Research via the Rocky Mountain Climate Organization

Devastating extreme rain events are part of a growing trend in the Midwest, according to a new report looking at 50 years of storm data.

Over the last five decades, the types of deluges that washed out towns in Iowa, forced the Army Corps of Engineers to intentionally blow up levees to save Cairo, Illinois, and sent the Missouri River over its banks for hundreds of miles, have been increasing, according to analysis by the Rocky Mountain Climate Organization (RMCO) and the Natural Resources Defense Council (NRDC).

Big storms, leading to big floods, are occurring with increasing frequency in the Midwest, with incidences of the most severe downpours doubling over the last half century. The report’s lead author, Stephen Saunders, explained that “a threshold may have been crossed”:

“Global studies already show that human-caused climate change is driving more extreme precipitation, and now we’ve documented how great the increase has been in the Midwest and linked the extreme storms to flooding in the region.

In addition to region-wide trends, the report presents trends in the eight Midwestern states.  For the worst storms (three inches or more of rain in 24 hours) from 1961-2011, the report outlines the following state-level trends:  Indiana (+160 percent); Wisconsin (+203 percent); Missouri (+81 percent); Michigan (+180 percent); Minnesota (+104 percent); Illinois (+83 percent); Ohio (+40 percent); and Iowa (+32 percent).

Key findings include:

• Since 1961, the Midwest has had an increasing number of large storms.  The largest of storms, those of three inches or more of precipitation in a single day, increased the most, with their annual frequency having increased by 103 percent over the roughly half century period through 2011. For storms of at least two inches but less than three inches in a day, the trend was a 81 percent increase; for storms of one to two inches, a 34 percent increase. Smaller storms did not have a significant increase.

• The rates of increase for all large storms accelerated over time, with the last analyzed decade, 2001-2010, showing the greatest jumps. For the largest storms, in 2001-2010 there were 52 percent more storms per year than in the baseline period.

• The frequency of extreme storms has increased so much in recent years that the first 12 years of this century included seven of the nine top years (since 1961) for the most extreme storms in the Midwest.

• With more frequent extreme storms, the average return period between two such storms has become shorter. In 1961-1970, extreme storms averaged once every 3.8 years at an individual location in the Midwest. That is two to four times more frequent than a major hurricane making landfall at a typical location along the U.S. coast from North Carolina to Texas. By 2001-2010, the average return period for Midwestern extreme storms at a single location was down to 2.2 years—or four to eight times more frequent than landfalling major hurricanes.

The report also presents new evidence linking extreme storms in the Midwest to major floods, the region’s most costly regularly occurring natural disasters.

The new analysis shows that the two worst years in the Midwest for storms of three inches or more per day were 2008 and 1993, the years with the Midwest’s worst floods in some 80 years, which caused $16 billion and $33 billion in damages and rank,  among the nation’s worst natural disasters. The report presents new evidence linking the 2008 flooding to extreme storms, showing that in areas with the worst flooding 48 percent of the local precipitation came from extreme storms.

In 2010, which ranked fourth among years in regional extreme-storm frequency, Iowa alone had $1 billion in agricultural losses from extreme storms. In 2011, which ranked fifth, Midwestern flooding caused $2 billion in damages. This shows how the Midwest is increasingly vulnerable to flooding if extreme precipitation continues to increase with human-caused climate change, as scientists consistently project will happen.

This research brief was originally published at the Rocky Mountain Climate Institute.

The situation in the country illustrates the cruel reality of “rollercoaster” extreme weather — a problem that will only be exacerbated by accumulating heat-trapping gases in the atmosphere. Recent research also finds that the loss of Arctic ice favors extreme, prolonged weather events “such as drought, flooding, cold spells and heat waves.”

The rain has certainly helped some regions. But other parts of England were so dry, it could take months of record rainfall to bring groundwater levels back to normal. One aquifer close to London is 90 percent below normal levels for this time of year.

Experts in the country are explaining why the combination of extremely dry and extremely wet conditions make it harder to recover from drought. Climatewire reported on the problem:

“Heavy rain on parched ground is like pouring water on an old, dry sponge. Much of it will bounce off. The sponge needs to be wet in order to hold the water. Farmers are in a much better position than they were thanks to the rains. River levels have risen, soil moisture has increased and their water reserves have been replenished. But aquifers take much longer to fill,” said a spokeswoman for England’s Environment Agency.

According to figures from the Environment Agency, 42 percent of groundwater “indicator sites” are “exceptionally low.”

“Over the last two winters, the amount of rainfall we have had has been down 20 to 30 percent on what we would normally have. Most of the recharge of groundwater happens over the winter. We lost three to four months of groundwater recharge in total over that two-year period,” [explained Andrew McKenzie of the British Geological Survey McKenzie to Climatewire.]

“We have now had the wettest April ever, and you might think that would go halfway to recharging the groundwater. But we also had a very dry March, and the soils had already switched to summer, dry mode and had to switch back,” he added.

Ironically, when the rains hit in April after a dry March, the Environment Agency issued 13 severe flood warnings and 42 flood alerts for areas around the country — all while homeowners were banned from watering their gardens.

This will eventually be normal weather under a business as usual emissions scenario.

According to a study from the National Center for Atmospheric Research, our current rate of emissions puts us on a path to dust bowl conditions in many areas of the world, while “precipitation may become more intense but less frequent (i.e., longer dry spells) under GHG-induced global warming. This may increase flash floods and runoff, but diminish soil moisture and increase the risk of agricultural drought.”

Related Posts:

• Must-See Video: Has Global Warming Caused A Quantum Jump In Extreme Weather?
• NOAA: Human-Caused Climate Change Already a Major Factor in More Frequent Mediterranean Droughts
• Study: Global warming is driving increased frequency of extreme wet or dry summer weather in southeast, so droughts and deluges are likely to get worse

Figure 1. The ten warmest 12-month periods in the contiguous U.S. since record keeping began in 1895. Image credit: NOAA/NCDC.

by Jeff Masters, via WunderBlog

The past twelve months were the warmest twelve months in U.S. history, said NOAA’s National Climatic Data Center (NCDC) on Tuesday, in their monthly “State of the Climate” report. Temperatures in the contiguous U.S. during May 2011 – April 2012 broke the previous record for warmest 12-month period, set November 1999 – October 2000, by 0.1°F. The past twelve months have featured America’s 2nd warmest summer, 4th warmest winter, and warmest March on record. Twenty-two states were record warm for the 12-month period, and an additional nineteen states were top ten warm. NOAA said that the January – April 2012 period was also the warmest January – April period since record keeping began in 1895. The average temperature of 45.4°F during January – April 2012 was 5.4°F above the 20th century average for the period, and smashed the previous record set in 2006 by an unusually large margin–1.6°F.

Figure 2. The average temperature of 45.4°F during January – April 2012 was the warmest on record: 5.4°F above the 20th century average for the period, and was 1.6°F above the previous record set in 2006. January – April temperatures have been rising at about 1.9°F per century since 1895. Image credit: NOAA/NCDC.

April 2012: 3rd warmest on record
April 2012 was the third warmest April in the contiguous U.S. since record keeping began in 1895. Ten states had a top-ten warmest April, and no states were cooler than average. But what’s really remarkable about April was that eight states–Illinois, Indiana, Kentucky, Michigan, Wisconsin, Ohio, Pennsylvania, and West Virginia–had average April temperatures cooler than their March temperatures, even though their April temperatures were still above the long-term average for the month. These statistics show just how remarkably warm March 2012 was. Most extreme was Illinois, where April 2012 temperatures ranked in the top 20% for warmest Aprils, yet were cooler than March 2012 temperatures.

Figure 3. Temperature rankings for April 2012 in the Contiguous U.S. Ten states had a top-ten warmest April, and no states were cooler than average. Image credit: NOAA/NCDC.

Figure 4. NOAA’s U.S. Climate Extremes Index (CEI) for January – April shows that 2012 had the most extreme weather on record.

Most extreme January – April on record
NOAA’s U.S. Climate Extremes Index (CEI), an index that tracks the highest 10 percent and lowest 10 percent of extremes in temperature, precipitation, and drought, was 42% during the January-April period, over twice the average value, and the greatest on record. Remarkably, 82% of the contiguous U.S. had maximum temperatures that were in the warmest 10% historically, and 68% had warm minimum temperatures in the top 10%, with records going back to 1910. The previous records were 56% (2000) and 57% (1992) for maximum and minimum temperatures, respectively. The percentage area of the U.S. experiencing top-10% drought conditions during January – April was 19%, which was the 17th greatest since 1910. Extremes in precipitation as computed by the CEI were near average for the January – April period.

– Jeff Masters co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990. This piece was originally published at the WunderBlog and was reprinted with permission.

That alarming conclusion comes from the National Research Council in a new report assessing the progress of the nation’s Earth observation programs. In short: our leading scientific institutions aren’t actually making much progress.

Rather, a lack of funding and infrastructure will result in “a rapid decline” in our ability to monitor extreme weather and changes to the climate.

The committee found that the number of NASA and NOAA Earth observing instruments in space is likely to decline to as little as 25 percent of the current number by 2020….  The U.S. system of environmental satellites is at risk of collapse.

The projected loss of observing capability could have significant adverse consequences for science and society. The loss of observations of key Earth system components and processes will weaken the ability to understand and forecast changes arising from interactions and feedbacks within the Earth system and limit the data and information available to users and decision makers. Consequences are likely to include slowing or even reversal of the steady gains in weather forecast accuracy over many years and degradation of the ability to assess and respond to natural hazards and to measure and understand changes in Earth’s climate and life support systems.

The report is a mid-term update of the NSA’s 2007 decadal survey — a proposed 10-year plan for improving earth sciences programs at NASA and the National Oceanic and Atmospheric Administration (NOAA). The NSA assessment did find that NASA was able to launch new satellites into space and work on international partnerships to make up for shortfalls in money; however, those won’t be enough to meet needed technology improvements.

There are three major factors contributing to this unprecedented decline in Earth monitoring capabilities: budget cuts, a rapidly aging fleet of satellites, and a lack of launch capabilities.

The budgetary issues have been ongoing. According to the NSA progress report, NASA’s Earth science program still hasn’t been funded to the requested $2 billion to meet future objectives.

And as Climate Progress reported last year, Republican lawmakers proposed slashing $1.2 billion from NOAA’s funding levels, cutting into satellite programs. The satellite programs were eventually funded to requested levels, but future funding is uncertain. Senate lawmakers have proposed moving NOAA’s satellite program over to NASA where operational efficiencies could potentially save money.

Officials at these agencies say that more money is needed to replace the fleet of aging satellites that will inevitably fail in the coming years. According to the NSA report, there’s also a severe lack of launch vehicles for Earth satellites that “directly threatens programmatic robustness.”

After all, satellites aren’t much good without a way to launch them.

What’s the solution? Increasing the budget for new satellite infrastructure is the most obvious. But a major boost in funding for these programs is unlikely. So the NSA report recommends establishing new partnerships and “balancing costs with science objectives and priorities” by focusing on a more diverse range of projects rather than a few high-profile missions.

Programmatic efficiency is key. But it still doesn’t fully address what could become a national crisis. As our planet overheats — making extreme weather more intense, deadly and expensive — our ability to monitor the health of planet is collapsing.

by Bill McKibben, via TomDispatch

The Williams River was so languid and lovely last Saturday morning that it was almost impossible to imagine the violence with which it must have been running on August 28, 2011. And yet the evidence was all around: sand piled high on its banks, trees still scattered as if by a giant’s fist, and most obvious of all, a utilitarian temporary bridge where for 140 years a graceful covered bridge had spanned the water.

The YouTube video of that bridge crashing into the raging river was Vermont’s iconic image from its worst disaster in memory, the record flooding that followed Hurricane Irene’s rampage through the state in August 2011.  It claimed dozens of lives, as it cut more than a billion-dollar swath of destruction across the eastern United States.

I watched it on TV in Washington just after emerging from jail, having been arrested at the White House during mass protests of the Keystone XL pipeline.  Since Vermont’s my home, it took the theoretical — the ever more turbulent, erratic, and dangerous weather that the tar sands pipeline from Canada would help ensure — and made it all too concrete. It shook me bad.

And I’m not the only one.

New data released last month by researchers at Yale and George Mason universities show that a lot of Americans are growing far more concerned about climate change, precisely because they’re drawing the links between freaky weather, a climate kicked off-kilter by a fossil-fuel guzzling civilization, and their own lives. After a year with a record number of multi-billion dollar weather disasters, seven in ten Americans now believe that “global warming is affecting the weather.” No less striking, 35% of the respondents reported that extreme weather had affected them personally in 2011. As Yale’s Anthony Laiserowitz told the New York Times, “People are starting to connect the dots.”

Which is what we must do. As long as this remains one abstract problem in the long list of problems, we’ll never get to it.  There will always be something going on each day that’s more important, including, if you’re facing flood or drought, the immediate danger.

But in reality, climate change is actually the biggest thing that’s going on every single day.  If we could only see that pattern we’d have a fighting chance. It’s like one of those trompe l’oeil puzzles where you can only catch sight of the real picture by holding it a certain way. So this weekend we’ll be doing our best to hold our planet a certain way so that the most essential pattern is evident. At 350.org, we’re organizing a global day of action that’s all about dot-connecting; in fact, you can follow the action at climatedots.org.

The day will begin in the Marshall Islands of the far Pacific, where the sun first rises on our planet, and where locals will hold a daybreak underwater demonstration on their coral reef already threatened by rising seas. They’ll hold, in essence, a giant dot — and so will our friends in Bujumbura, Burundi, where March flooding destroyed 500 homes. In Dakar, Senegal, they’ll mark the tidal margins of recent storm surges.  In Adelaide, Australia, activists will host a “dry creek regatta” to highlight the spreading drought down under.

Pakistani farmers — some of the millions driven from their homes by unprecedented flooding over the last two years — will mark the day on the banks of the Indus; in Ayuthaya, Thailand, Buddhist monks will protest next to a temple destroyed by December’s epic deluges that also left the capital, Bangkok, awash.

Activists in Ulanbataar will focus on the ongoing effects of drought in Mongolia.  In Daegu, South Korea, students will gather with bags of rice and umbrellas to connect the dots between climate change, heavy rains, and the damage caused to South Korea’s rice crop in recent years. In Amman, Jordan, Friends of the Earth Middle East will be forming a climate dot on the shores of the Dead Sea to draw attention to how climate-change-induced drought has been shrinking that sea.

In Herzliya, Israel, people will form a dot on the beach to stand in solidarity with island nations and coastal communities around the world that are feeling the impact of climate change. In newly freed Libya, students will hold a teach-in.  In Oman, elders will explain how the weather along the Persian Gulf has shifted in their lifetimes. There will be actions in the cloud forests of Costa Rica, and in the highlands of Peru where drought has wrecked the lives of local farmers.  In Monterrey, Mexico, they’ll recall last year’s floods that did nearly $2 billion in damage. In Chamonix, France, climbers will put a giant red dot on the melting glaciers of the Alps.

And across North America, as the sun moves westward, activists in Halifax, Canada, will “swim for survival” across its bay to highlight rising sea levels, while high-school students in Nashville, Tennessee, will gather on a football field inundated by 2011’s historic killer floods.

In Portland, Oregon, city dwellers will hold an umbrella-decorating party to commemorate March’s record rains. In Bandelier, New Mexico, firefighters in full uniform will remember last year’s record forest fires and unveil the new solar panels on their fire station.  In Miami, Manhattan, and Maui, citizens will line streets that scientists say will eventually be underwater. In the high Sierra, on one of the glaciers steadily melting away, protesters will unveil a giant banner with just two words, a quote from that classic of western children’s literature, The Wizard of Oz. “I’m Melting” it will say, in letters three-stories high.

This is a full-on fight between information and disinformation, between the urge to witness and the urge to cover-up. The fossil-fuel industry has funded endless efforts to confuse people, to leave an impression that nothing much is going on.  But — as with the tobacco industry before them — the evidence has simply gotten too strong.

Once you saw enough people die of lung cancer, you made the connection. The situation is the same today.  Now, it’s not just the scientists and the insurance industry; it’s your neighbors. Even pleasant weather starts to seem weird.  Fifteen thousand U.S. temperature records were broken, mainly in the East and Midwest, in the month of March alone, as a completely unprecedented heat wave moved across the continent.  Most people I met enjoyed the rare experience of wearing shorts in winter, but they were still shaking their heads. Something was clearly wrong and they knew it.

The one institution in our society that isn’t likely to be much help in spreading the news is… the news. Studies show our papers and TV channels paying ever less attention to our shifting climate.  In fact, in 2011 ABC, CBS, NBC, and Fox spent twice as much time discussing Donald Trump as global warming. Don’t expect representatives from Saturday’s Connect the Dots day to show up on Sunday’s talk shows.  Over the last three years, those inside-the-Beltway extravaganzas have devoted 98 minutes total to the planet’s biggest challenge. Last year, in fact, all the Sunday talk shows spent exactly nine minutes of Sunday talking time on climate change — and here’s a shock: all of it was given over to Republican politicians in the great denial sweepstakes.

So here’s a prediction: next Sunday, no matter how big and beautiful the demonstrations may be that we’re mounting across the world, “Face the Nation” and “Meet the Press” won’t be connecting the dots. They’ll be gassing along about Newt Gingrich’s retirement from the presidential race or Mitt Romney’s coming nomination, and many of the commercials will come from oil companies lying about their environmental efforts. If we’re going to tell this story — and it’s the most important story of our time — we’re going to have to tell it ourselves.

This post was originally published at TomDispatch and was reprinted with permission.

Bill McKibben, a TomDispatch regular, and the author, most recently, of Eaarth: Making a Life on a Tough New Planet, is the founder of 350.org, which is coordinating Saturday’s Connect the Dots day.  You can find the event nearest you by checking climatedots.org.

Countless lives were saved this weekend by vigilant government officials who warned of deadly tornadoes in Oklahoma, Kansas, Iowa, Nebraska — states whose politics are dominated by anti-government, anti-science ideologues. Over 100 tornadoes struck down in 24 hours, but only six people died in Oklahoma, Sen. Jim Inhofe’s home state, thanks to warnings from the National Weather Service scientists he has worked to discredit:

The tornadoes were unrelenting – more than 100 in 24 hours over a stretch of the Plains states. They tossed vehicles and ripped through homes. They drove families to their basements and whipped debris across small towns throughout the Midwest. In some areas, baseball-size hail rained from the sky.

And yet, in a stroke that some officials have attributed to a more vigilant and persistent warning system, relatively few people were killed or injured.

Wichita, Kansas, the headquarters of Koch Industries, suffered $280 million in damage from a ferocious twister, but the “ever-increasing government” demonized by the Koch brothers prevented any loss of life.

Greenhouse pollution from the fossil fuel industries that control the region’s politics is making our weather more extreme and dangerous. The heat trapped by carbon pollution is powering these earlier and more intense storms with record-warm waters in the Gulf of Mexico. As Dr. Jeff Masters wrote on Friday:

This is the warmest March value on record for the Gulf of Mexico, going back over a century of record keeping. During the first two weeks of April, Gulf of Mexico waters remained about 1.5°C above average, putting April on pace to have the warmest April water temperatures on record. Only one year in the past century has had April water temperatures in the Gulf of Mexico more than 1.1°C above average; that year was 2002 (1.4°C above average.) All that record-warm water is capable of putting record amounts of water vapor into the air, since evaporation increases when water is warmer. Because moist air is less dense than dry air, this warm, moist air flowing northwards from the Gulf of Mexico into the developing storm system over the Plains will be highly unstable once it encounters cold, dry air aloft. The record-warm waters of the Gulf of Mexico are a key reason for the high risk of severe weather over the Plains this weekend.

Related Post:

• Tornadoes, Extreme Weather and Climate Change, Revisited

Host Carol Costello said, it’s “such a strange spring,” leading Steele to say

“It really is. That’s kind of the climate change we are seeing. You know, extremes are kind of ruling the roost and really what we are seeing, more become the norm.”

Costello said it made her “afraid” about what might happen next spring, to which Steele replied:

“This global warming is really kind of a misnomer. It’s global climate change. So the colds are colder and warms are warmer and severe is more severe.”

Watch it:

Thanks to this off the charts extreme weather and the growing body of scientific literature attributing it to human-caused global warming, we are starting to see more and more journalists, meteorologists and climate scientists make the connection.

Record-setting hailstone from the Hawaii 'supercell' thunderstorm that hit Oahu on March 9. Credit: NOAA.

by Jeff Masters, via the WunderBlog

A hailstone with the diameter of roughly that of a grapefruit that hit Oahu on March 9, 2012, has been confirmed as the largest hailstone on record for the state of Hawaii, according to NOAA.

The record-setting hailstone was dropped by a “supercell” thunderstorm on the windward side of Oahu. There were numerous reports of hail with diameters of 2 to 3 inches and greater. Hail the size of a penny (diameter of 3/4 inch) or quarter (diameter of one inch) has been reported in Hawaii only eight times since records began, and there is no record of hail larger than 1 inch in diameter. Hail the size of golf balls and baseballs can only form within intense thunderstorms called supercells. These supercells need warm, moist air to rise into progressively colder, drier air, as well as winds changing direction and increasing speed with increasing height off the ground.

For both sets of conditions to exist at the same time in Hawaii is extremely rare, but that did occur on March 9. Conditions that day were ideal for a supercell to form, and the storm looked very much like supercell thunderstorms common in the Central U.S. during spring. Supercells can also produce tornadoes, another rarity in Hawaii. The same hail-producing supercell produced a confirmed EF-0 tornado with winds of 60-70 mph in Lanikai and Enchanted Lakes on Oahu.

Jeff Masters is the co-founder of the Weather Underground, where this piece was originally published.

IPCC (2001) graph illustrating how a shift and/or widening of a probability distribution of temperatures affects the probability of extremes. (Via RealClimate)

The full 592-page (!) IPCC extreme weather report is out. Like most Intergovernmental Panel on Climate Change reports it has some value for people who don’t follow the science closely, which is to say the overwhelming majority of the media and policymakers.

Of course, the TV media ignored the summary report in November, so we will have to see if they pay any attention to this one now that the United States has just been through the most extreme winter heat wave in our recorded history.

But as Kevin Trenberth, one of the world’s leading experts on the link between climate change and extreme weather, put it to me in an email:

I have seen the chapter on the physical climate and I found it quite disappointing…. I don’t think it adds to AR4 [IPCC Fourth Assessment] much.

I agree with Trenberth that if, for instance, you want a more up to date and straightforward discussion of the impact of climate change on precipitation, you should just read his 2011 paper, “Changes in precipitation with climate change” (online here).

Indeed, the actual scientific literature from 2011 is generally more useful than this report — see “NOAA Study Finds Human-Caused Climate Change Already a Major Factor in More Frequent Mediterranean Droughts” and Hansen et al: “Extreme Heat Waves … in Texas and Oklahoma in 2011 and Moscow in 2010 Were ‘Caused’ by Global Warming.”

It is, as I wrote when the summary came out in November, the report is “Another Blown Chance to Explain the Catastrophes Coming If We Keep Doing Nothing.”  I also wrote that the summary has a good chart that hints at dust-bowlification, but is mostly silent on warming’s gravest threat to humanity.

The full report has more on drought, but fails to clearly describe what the literature now suggests is coming if we stay anywhere near our current emissions path. In 2010, the National Center for Atmospheric Research did a far more valuable literature review and analysis of what we face, which makes clear we risk multiple, devastating global droughts even on moderate emissions path.

In the case of extreme weather, my guess is that decades from now, people will look back on the staggering growth in off-the-charts “outlandish” extreme events in the past few years and conclude that a regime change had occurred in the climate. That change is probably a combination of the sharp loss in summer/fall Arctic sea ice and the sharp increase in ocean heat content.

We’re only in the past year or so seen analyses that demonstrate the human fingerprint in these uber-extreme events, including the studies above and these two:

• Nature Climate Change: Strong Evidence Manmade ‘Unprecedented Heat And Rainfall Extremes Are Here … Causing Intense Human Suffering’
• Study Finds 80% Chance Russia’s 2010 July Heat Record Would Not Have Occurred Without Climate Warming

So rather than citing this timely, but already out-of-date IPCC report, let me just repost below an excellent new piece from RealClimate by the authors of those two studies, who have been doing some of the best recent work in this area.

Extremely hot

By Stefan Rahmstorf and Dim Coumou

One claim frequently heard regarding extreme heat waves goes something like this: ”Since this heat wave broke the previous record by 5 °C, global warming can’t have much to do with it since that has been only 1 °C over the 20th century”. Here we explain why we find this logic doubly flawed.

One can ask two different questions about the influence of global warming on heat waves (Otto et al. 2012), and we take them in turn.

1. How much hotter did global warming make this heat wave?

We have some trouble with framing the question like this, because it tacitly assumes that the same weather situation would have also arisen without global warming, only at a (say) 1 °C lower temperature level. That need not be the case, of course, since weather is highly stochastic and global warming can also affect the circulation patterns of the atmosphere.

But even if we accept the basic premise (and it could be meant in a purely statistical sense, although that is not usually how it is expressed), would an average anthropogenic warming by 1 °C in the relevant location mean that 1 °C is also the amount added to an extreme event? Only in a linear climate system. Imagine a heat wave that pushes temperatures up to 30 °C in a world without global warming. In the same weather situation with global warming, you might expect that this weather then results in a 31 °C heat wave. But that could well be wrong. Possibly in the situation with warming, the soil has dried out over the previous months because of that extra 1 °C. So now you lost evaporative cooling, the incoming sunlight turns into sensible heat rather than a large fraction going into latent heat. That is a non-linear feedback, and not an imagined one. Detailed studies have shown that this may have played an important role during the European heat wave of 2003 (Schär et al. 2004).

The basic phenomenon is familiar to oceanographers: if the mean sea level in one location rises by 30 cm, this does not mean that the high-tide level also rises by 30 cm. In some cases it will be more, due to nonlinear feedback. I.e., a higher water level increases the flow cross-section (think of a tidal inlet) and reduces bottom friction so the tide rolls in faster, reaching a higher peak. The tidal range increases as well as the mean sea level.

Numerous other non-linear mechanisms are possible, which we are only beginning to understand – think of the recent studies that show how changes in snow cover or sea ice cover as a result of global warming affect weather systems. Or think of factors that could affect the stability of particularly strong blocking events. Thus, we’d be very cautious about making an essentially linear, deterministic argument about heat extremes to the public.

In the scientific literature, the influence of global warming on extreme events is therefore usually discussed in terms of probabilities, which is more fitted to stochastic events. The typical question asked is:

2. How much more likely did global warming make this heat wave?

For this question, it is easily shown that the logic “the greater the extreme, the less global warming has to do with it” is seriously flawed. The change in probability of certain temperature values being reached can be visualised with a probability density function (see Figure [above]). The probability distribution could be shifted unchanged towards warmer values, or it could be widened, or a combination of both (or some other deformation).

For illustration, let’s take the most simple case of a normal distribution that is shifted towards the warm end by a given amount – say one standard deviation. Then, a moderately extreme temperature that is 2 standard deviations above the mean becomes 4.5 times more likely (see graph below). But a seriously extreme temperature, that is 5 standard deviations above the mean, becomes 90 times more likely! Thus: the same amount of global warming boosts the probability ofreally extreme events, like the recent US heat wave, far more than it boosts more moderate events. This is exactly the opposite of the claim that “the greater the extreme, the less global warming has to do with it.” The same is also true if the probability distribution is not shifted but widened by a constant factor. This is easy to show analytically for our math-minded readers.

Graph illustrating how the ratio of the probability of extremes (warmed climate divided by unchanged climate – this increased likelihood factor is shown as a dashed line, scale on right) depends on the value of the extreme.

So in summary: even in the most simple, linear case of a shift in the normal distribution, the probability for “outlandish” heat records increases greatly due to global warming. But the more outlandish a record is, the more would we suspect that non-linear feedbacks are at play – which could increase their likelihood even more.

P.s.

Our Perspective article on the unprecedented extremes of the last decade was just published by Nature Climate Change: Coumou & Rahmstorf (2012) A decade of weather extremes (paywalled)

References:

Otto et al., Reconciling two approaches to attribution of the 2010 Russian heat wave, Geophysical Research Letters 2012, VOL. 39, L04702, doi:10.1029/2011GL050422

Schär, C. et al. The role of increasing temperature variability in European summer heat waves. Nature 427, 332–336 (2004).

– Stefan Rahmstorf and Dim Coumou

It is very likely that several of the unprecedented extremes of the past decade would not have occurred without anthropogenic global warming.

That’s the conclusion of a major new analysis of the scientific evidence in Nature Climate Change, “A decade of weather extremes” (subs. req’d). The research is by Dim Coumou and Stefan Rahmstorf of Germany’s Potsdam Institute for Climate Impact Research.

The study includes this table of extreme events — “The selection criterion for this (incomplete) list was that the event was documented to be record-breaking (that is, unprecedented) in a long measurement series”:

The study points out how devastating some of these events have been for people:

The Moscow heatwave and Pakistan flooding that year illustrated how destructive extreme weather can be to societies: the death toll in Moscow has been estimated at 11,000 and drought caused grain-harvest losses of 30%, leading the Russian government to ban wheat exports. At the same time Pakistan was hit by the worst flooding in its history, which affected approximately one-fifth of its total land area and 20 million people.

It explains that the context for these events is unprecedented human-caused global warming:

The unprecedented meteorological events listed in Table 1 occurred in a decade that was likely the warmest globally for at least a millennium

A number of these individual events have been the subject of “attribution” analysis  making clear that they would have been extremely unlikely to have happened without human caused global warming (see Hansen et al: “Extreme Heat Waves … in Texas and Oklahoma in 2011 and Moscow in 2010 Were ‘Caused’ by Global Warming” and ”Study Finds 80% Chance Russia’s 2010 July Heat Record Would Not Have Occurred Without Climate Warming,” also by Rahmstorf and Coumou).

In addition, we’ve had analyses link recent drought and dust-bowlification to warming — see NOAA Bombshell: Human-Caused Climate Change Already a Major Factor in More Frequent Mediterranean Droughts:

“The magnitude and frequency of the drying that has occurred is too great to be explained by natural variability alone,” said Martin Hoerling, Ph.D. of NOAA’s Earth System Research Laboratory in Boulder, Colo., lead author.

The new study was of course completed before the blow-out, all-time record winter/spring heat wave, which many leading experts have said bears the fingerprints of human-caused warming.

Clearly, the more unprecedented climate extremes that we see, the stronger the case grows for the overall human fingerprint (see also Eight Must-Have Charts Summarize the Evidence for a “Human Fingerprint” on Recent Climate Change).

The powerful conclusion of this study builds off of Hansen’s famous 1988 testimony:

In 1988, Jim Hansen famously stated in a congressional hearing that “it is time to stop waffling so much and say that the evidence is pretty strong that the greenhouse effect is here”. We conclude that now, more than 20 years later, the evidence is strong that anthropogenic, unprecedented heat and rainfall extremes are here — and are causing intense human suffering.

What is most worrisome is that manmade warming is causing intense human suffering now, and we have only warmed 1.4°F in the past century. We’re projected to warm more than 5 times that this century if we are foolish enough to stay anywhere near our current emissions path.

Climate Progress has written many times about the 2009 study on the increase in the ratio of heat records to cold records in the United States, “spurred by a warming climate.”

The new study has an good analysis and chart on the increase in the number of monthly heat records worldwide:

Monthly heat extremes document the most persistent and thus destructive heatwaves. Their number increases faster with climate change than do daily extremes, because more-aggregated data has smaller variance and the number increases in proportion to the ratio of warming trend to variance. The number of observed local monthly heat records around the globe is now more than three times as high as expected in a stationary climate (Fig. 2). This observed increase is consistent with that expected from a simple stochastic model including the warming trend. For Moscow, which has experienced strong warming in the past 30 years, this model even gives a fivefold increase in the expected number of monthly heat records. Extremely hot summers (exceeding three standard deviations) are now observed in about 10% of the global land area, compared with only about 0.1–0.2% for the period from 1951 to 1980….

Results from modelling attribution studies are consistent with these observations: the risk of a heatwave of the magnitude of the 2003 European event has at least doubled but probably quadrupled (best estimate) as a result of human influence on climate.

Ten-year running averages of the number of unprecedented records in monthly mean temperature in 204 time series are shown, namely 17 weather stations from around the world for each calendar month, given as the ratio of the observed number of extremes to that expected in a stationary climate.

The study has an extended discussion in the conclusion about media coverage of extreme events and the famous “loaded dice” analogy:

Many climate scientists (including ourselves) routinely answer media calls after extreme events with the phrase that a particular event cannot be directly attributed to global warming. This is often misunderstood by the public to mean that the event is not linked to global warming, even though that may be the case — we just can’t be certain. If a loaded dice rolls a six, we cannot say that this particular outcome was due to the manipulation — the question is ill-posed. What we can say is that the number of sixes rolled is greater with the loaded dice (perhaps even much greater). Likewise, the odds for certain types of weather extremes increase in a warming climate (perhaps very much so). Attribution is not a ‘yes or no’ issue as the media might prefer, it is an issue of probability. It is very likely that several of the unprecedented extremes of the past decade would not have occurred without anthropogenic global warming. Detailed analysis can provide specific numbers for certain types of extreme, as in the examples discussed above.

Climatologist Kevin Trenberth takes a somewhat different view in his new Climatic Change piece, which I reposted over the weekend. He also thinks the question is ill-posed:

The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be….

The air is on average warmer and moister than it was prior to about 1970 and in turn has likely led to a 5–10 % effect on precipitation and storms that is greatly amplified in extremes. The warm moist air is readily advected onto land and caught up in weather systems as part of the hydrological cycle, where it contributes to more intense precipitation events that are widely observed to be occurring.

I had asked Rahmstorf  about the dice analogy when I interviewed him for his earlier study on the Russian heat wave.  I specifically asked him about whether one could say that we had not just loaded the dice but painted higher numbers on the dice. He said:

Painting higher numbers on the dice is a good analogy. There are new records that we haven’t seen before.

Rahmstorf’s new study has collected a variety of those — and we keep experiencing new ones, such as the “spring heat wave like no other in U.S. and Canadian history.”

Finally, the Potsdam Institute’s news release explains some of the background of the study for those who don’t subscribe to the journal:

Three pillars: basic physics, statistical analysis and computer simulations

The scientists base their analysis on three pillars: basic physics, statistical analysis and computer simulations. Elementary physical principles already suggest that a warming of the atmosphere leads to more extremes. For example, warm air can hold more moisture until it rains out. Secondly, clear statistical trends can be found in temperature and precipitation data, the scientists explain. And thirdly, detailed computer simulations also confirm the relation between warming and records in both temperature and precipitation.

With warmer ocean temperatures, tropical storms – called typhoons or hurricanes, depending on the region – should increase in intensity but not in number, according to the current state of knowledge. In the past decade, several record-breaking storms occurred, for example hurricane Wilma in 2004. But the dependencies are complex and not yet fully understood. The observed strong increase in the intensity of tropical storms in the North Atlantic between 1980 and 2005, for example, could be caused not just by surface warming but by a cooling of the upper atmosphere. Furthermore, there are questions about the precision and reliability of historic storm data.

To repeat the bottom line: “The evidence is strong that anthropogenic, unprecedented heat and rainfall extremes are here — and are causing intense human suffering.”

The time to act is now.

Related Post:

• Two seminal Nature papers join growing body of evidence that human emissions fuel extreme weather, flooding that harm humans and the environment
• Study: Global warming is driving increased frequency of extreme wet or dry summer weather in southeast, so droughts and deluges are likely to get worse
• Russian President Medvedev: “What is happening now in our central regions is evidence of this global climate change, because we have never in our history faced such weather conditions in the past”

The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question. All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be….

The air is on average warmer and moister than it was prior to about 1970 and in turn has likely led to a 5–10 % effect on precipitation and storms that is greatly amplified in extremes. The warm moist air is readily advected onto land and caught up in weather systems as part of the hydrological cycle, where it contributes to more intense precipitation events that are widely observed to be occurring.

Seasonal Jun-Jul-Aug 2010 sea surface temperature (SST) anomalies relative to 1951–70. Record high SSTs were recorded in the locations and at the times indicated with record flooding nearby.

Kevin E. Trenberth, senior scientist, National Center for Atmospheric Research, in the journal Climatic Change, released under a Creative Commons-Attribution license (PDF here, HTML here)

Framing the way to relate climate extremes to climate change

3 Some examples of recent climate extremes

3.1 SSTs

ENSO played a major role in climate extremes in 2010 and 2011 (TF12). El Niño conditions persisted through April 2010 but rapidly gave way to La Niña conditions by June. The SST anomalies for the northern summer (JJA) of 2010 (Fig. 1) reveals the La Niña conditions in the Pacific and hence the cooler than normal conditions mean that this was the region where the thunderstorms, tropical storms, and other convective activity were not occurring. However, as shown in TF12, very high SST anomalies from 0.5 to 1.5 °C, indeed record high SSTs in many instances (Fig. 1), occurred in the Indian Ocean and Indonesian region as well as throughout the tropical Atlantic (relative to a 1951–1970 normal that precedes most anthropogenic warming), regions that are normally very warm anyway (TF12). The total SSTs exceeded 29 °C over broad regions and were at an all time high in May 2010 (30.4 °C) in the northern Indian Ocean encompassing the Arabian Sea and Bay of Bengal (TF12). SSTs were also very high (second highest on record) north of Australia for September to November 2010, and by December they were the highest on record for that month. SST anomalies were also highest on record in the Gulf of Mexico in August 2010 and in the Caribbean in September 2010 (TF12). In 2011, SSTs were well above normal in the Gulf of Mexico in April but had cooled off by May. However, SSTs were still very high in the tropical Atlantic.

Fig. 1 Seasonal Jun-Jul-Aug 2010 SST anomalies relative to 1951–70, based on HADISST data (Rayner et al. 2003). Record high SSTs were recorded in the locations and at the times indicated with record flooding nearby

---

Because the water holding capacity of the atmosphere increases exponentially with temperature (e.g., Trenberth et al. 2003), a positive anomaly on top of already high SSTs has much greater effect than if located elsewhere. Indeed, the high SSTs were accompanied by very high water vapor amounts. The high SSTs provide ample moisture to the atmosphere and the resulting evaporative cooling of the ocean dropped the subsequent SST values down, but meanwhile heavy rains, often record breaking in intensity, occurred nearby to where the winds carried the moisture. This happened in China, India and Pakistan (June to early August 2010); Queensland, Australia (December 2010 and January 2011), and Colombia (October to December 2010) (Fig. 1). It also seems to have been a factor from 19 to 25 April 2011 when exceptionally heavy rains, exceeding 300 mm, occurred over southern Missouri, parts of Arkansas, eastern Oklahoma, and southern Illinois, and extended along the Ohio River Valley http://earthobservatory.nasa.gov/IOTD/view.php?id=50243, as a prelude to the flooding in the Mississippi.

3.2 La Niña and the Americas

La Niña conditions are well known to be associated with major anomalies in the Americas, and precipitation and flooding risk increase substantially in northern South America, such as in Colombia (Poveda et al. 2011). In La Niña summer and autumn the hurricane season is more active owing to a more favorable tropical circulation that allows storms to form in an environment of reduced wind shear and stability (Vecchi et al. 2008).

The SSTs (Fig. 1) in the Atlantic sector throughout the region north of Colombia were above 29 °C from July to September, and August 2010 was the warmest on record in both the Caribbean and in the Gulf of Mexico: anomalies exceeded 0.5–1.5 °C relative to the 1971–2000 base period (Fig. 1) (TF12). SST anomalies were especially large off the Colombian coast. The much cooler conditions to the west of the Central American isthmus both in absolute and anomaly terms understandably focused convective activity as a whole into the Atlantic and away from the Pacific. North of the equator, the result was a much above normal Atlantic hurricane season, in which there were 19 named storms, and 12 hurricanes, of which 4 were category 4 or 5, likely making it the second most active year after 2005. These aspects related to specific extremes are documented in TF12, including links between the heavy rains and the Russian heat wave of 2010, and the Colombian rains and the drought in the Amazon.

When La Niña is present, it strongly influences where the storms track across the United States, and the storms track in such a way as to miss the South. Consequently, Texas and surrounding areas (especially parts of Arizona, New Mexico and Oklahoma) suffered severe drought, and subsequently heat waves and wild fires in the northern spring and summer 2011. Nevertheless in spring, the storms crossing the central Midwest were able to link up with the warm moist air from the Gulf of Mexico, creating extra instability and buoyancy for the air that was entrained into the storms. This led to extensive heavy rains, flooding and tornado outbreaks. The pattern of rainfall in the spring is characteristic of La Niña although the extreme nature of the changes is not. The intense heat wave and “exceptional drought” continued in Texas through August. Many of these events are described in detail on line at the NOAA National Climatic Data Center, State of the Climate, Global Hazards site: http://www.ncdc.noaa.gov/sotc/hazards/2010/m (or 2011/m) where m is the month.

In spring, when land-sea contrasts transition to zero, strong westerly winds blow from the Pacific Ocean across the United States. Because the Rockies block the wind at low levels, the result is a strong westerly jet stream aloft while at low levels the air east of the Rockies comes from elsewhere including the Gulf of Mexico when there is a pronounced southerly component ahead of cold fronts. Both the change in wind speed and direction with height (southerlies at low levels, strong westerlies aloft) create wind shear, which sets the stage for super-cell thunderstorms to form tornadoes as the shear gets converted into rotation. According to NOAA, there were 539 deaths from over 1075 (actual count) tornadoes in April and May 2011 in the United States, the most deadly on record. Trends in the tornado record are not reliable, as increases in population over previously rural areas lead to more reporting of tornadoes, but the exceptional nature of the 2011 spring is not in doubt.

Global warming does not contribute directly to tornadoes themselves, but it does contribute to the vigor of the thunderstorms that host them through the increased warmth and moisture content (moist static energy) of the low level air flow. The increase in buoyancy of the air flowing through the Gulf of Mexico helps fuel the storms. Similarly, the extra moisture provided incremental amounts to the heavy rains that ultimately led to flooding along the Mississippi and later, farther north, heavy rains and melting snows contributed to extensive flooding of the Missouri River.

3.3 The Asian sector

The heavy rains and flooding in China, India, and Pakistan in JJA 2010 were associated with the very high SSTs to the south (Fig. 1) that provided extra moisture for the monsoon rains. The strong monsoon circulation then played a role in the Russian heat wave from mid-June to mid-August 2010 (Barriopedro et al. 2011; TF12), perhaps not unlike that in 2003 (Black and Sutton 2007) although influences from the Atlantic likely also played a role. The drought and famine in East Africa was also related to the high Indian Ocean SSTs (Williams and Funk 2011). Very large anomalies also existed at this time in Arctic sea ice and, in conjunction with positive Arabian Sea SST anomalies, connections to the events in Eurasia are suggested (Sedláček et al. 2011).

In the Asian sector, as the northern monsoon faded in late August of 2010, activity began to pick up in Australia, which switched to become very wet in September, continent wide, again reflecting the very high SSTs to the north (second highest on record), abundant moisture and the La Niña conditions. This was a fore-runner to the exceptionally heavy rains in Queensland in December 2010, and January 2011 where the southern monsoon rains kicked in with the presence of record high SSTs. Category 5 hurricane Yasi made landfall in Queensland in early February 2011.

4 Conclusions

References

Contiguous U.S. temperatures for winter (the months of December – January – February), from 1895 – 2012. The winter of 2011 – 2012 was the 4th warmest winter on record, behind 2000, 1999, and 1992. Winter temperatures have increased by abot 1.7°F per century (red linear trend line.) Image credit: National Climatic Data Center.

by Jeff Masters, excerpted from the WunderBlog

February is gone, and the non-winter of 2011 – 2012 is the history books as the fourth warmest in U.S. history, said NOAA’s National Climatic Data Center yesterday. The winter average temperature of 36.8°F was just 0.4°F cooler than the warmest winter on record, the winter of 1999 – 2000. If you lived in the Northern Plains, Midwest, Southeast and Northeast, it seemed like winter never really arrived this year–27 states in this region had top-ten warmest winters. Across the U.S., only New Mexico (41st coolest) and Alaska (35th coolest) had winter temperatures colder than average. According to NOAA’s Climate Extremes Index, the percent area of the U.S. experiencing extremes in warm maximum temperatures (top 10% on record) was 49 percent–the 4th highest value since the index began being computed in 1911. Jackson, Kentucky, Mount Pocono, Pennsylvania, and Trenton, New Jersey all had their warmest winter on record.

Contiguous U.S. temperature rankings for the winter of 2011 – 2012 (the months of December – January – February.) The 117-year period of record begins in 1895, and each state is given a ranking based on how cold this winter was, relative to the other 116 years. Thus, a ranking of 116 means it was the 2nd warmest winter on record. Image credit: NCD.

Third least snowy winter on record for the contiguous U.S.
Warm and dry conditions during the winter of 2011 – 2012 led to snow cover extent that was the 3rd lowest in the 46-year satellite record, according to data from the Rutgers Global Snow Lab. Snowfall was particularly low across parts of the West, where much of California, Nevada, and Arizona had a snowpack less than half of average. Fortunately, the West had a near-record snowpack the previous winter, so this year’s lack on snow will not cause serious water availability problems during the summer. In the Upper Midwest, the lack of a winter snowpack will substantially reduce the chances of spring flooding along the Mississippi and Missouri rivers. NOAA issues their annual spring flood outlook on March 15, and it is likely to show a much lower risk of flooding compared to last year, when 1-in-100 to 1-in-500 year floods hit much of the Missouri and Lower Mississippi rivers. However, the remarkably low snow cover this winter over the Upper Midwest will allow soils to dry out much more quickly than usual, leading to increased chances of summer drought. The latest Drought Monitor map shows moderate to severe drought covering nearly all of Minnesota and Northwest Iowa; these regions are at high risk of suffering damaging drought conditions during the summer growing season.

State-by-state rankings of precipitation for the winter of 2011 – 2012. Four Western states had a top-ten driest winters on record, and Kansas had a top-ten wettest winter. Drought-stricken Texas, which entered the winter expecting drier than average conditions, since it was a La Niña year, lucked out, getting an unusually wet winter. Records go back to 1895. Image credit: NCDC.

– Jeff Masters is Co-founder of the Weather Underground. This piece was originally published at the WunderBlog.

Related Post:

• ABC News Explains Warm Winter, ‘Wild Swings In Weather’, Driven by Global Warming, Only Going to Get Worse

Scientist: “The planet is getting warmer and it will continue to warm, on average, as we go into the future.”

ABC News: “That means we are in for more extreme weather, more Snowmageddon type winters and torrential downpours that can flood entire towns.”

Here’s the whole story from Wednesday night, which warns the public about “the wild swings in the weather we can expect in the future.”

Kudos to ABC for talking to a climate scientist and explaining how warming drives the extreme weather we’re seeing. They seem to be doing some of the best reporting on this:

• With No End in Sight for Texas Drought, ABC News Explains: “Every Farmer in the World Will Be Affected by Climate Change”
• Another terrific ABC News story — on the role global warming is playing in extreme winter weather
• Terrific ABC News story: “Raging Waters In Australia and Brazil Product of Global Warming”

NBC: “It’s as if a huge chunk of the country has suffered a deep, deep scar.”

National Weather Service Warnings for Past Week

The unexpectedly fierce and fast tornado outbreak so early in the season has folks asking again about a possible link to climate change. Climatologist Dr. Kevin Trenberth emailed me that, because of climate change, “there is every expectation that the [tornado] season will move up in time.  The warm winter in the US is perhaps an indicator of the nature of the changes to be expected.”

The former head of the Climate Analysis Section of the National Center for Atmospheric Research stands by his 2011 statement, “It is irresponsible not to mention climate change in stories that presume to say something about why all these storms and tornadoes are happening.” Below is some clarification of the context of that quote that he added. Trenberth also said:

Joe, what we can say with confidence is that heavy and extreme precipitation events often associated with thunderstorms and convection are increasing and have been linked to human-induced changes in atmospheric composition.

Insured losses due to thunderstorms and tornadoes in the U.S. in 2011 dollars. Data and image from Property Claims Service, Munich Re.

After April 2011 saw records set for most tornadoes in a month and in 24 hours, I examined the link in great detail here, looking at the data, the literature, and expert analysis.  That piece concluded:

1. When discussing extreme weather and climate, tornadoes should not be conflated with the other extreme weather events for which the connection is considerably more straightforward and better documented, including deluges, droughts, and heat waves.
2. Just because the tornado-warming link is more tenuous doesn’t mean that the subject of global warming should be avoided entirely when talking about tornadoes.

This post will run through the scientific literature along with some analyses from this year and last by leading experts.

First, though, some of the details on this week’s tornado outbreak.

MONDAY UPDATE: USA Today has a good piece, ”Warm winter helped fuel tornado outbreak,” which cites today’s post by Weather Underground meteorologist Dr. Jeff Masters

This year’s unusually mild winter has led to ocean temperatures across the Gulf of Mexico that are approximately 1°C above average–among the top ten warmest values on record for this time of year, going back to the 1800s. (Averaged over the month of February, the highest sea surface temperatures on record in the Gulf between 20 – 30°N, 85 – 95°W occurred in 2002, when the waters were 1.34°C above average). Friday’s tornado outbreak was fueled, in part, by high instability created by unusually warm, moist air flowing north from the Gulf of Mexico due to the high water temperatures there. This exceptionally warm air set record high temperatures at 28 airports in Louisiana, Arkansas, Mississippi, Alabama, Tennessee, Kentucky, and Georgia the afternoon of the tornado outbreak (March 2.) Cold, dry air from Canada moved over the outbreak region at high altitudes. This created a highly unstable atmosphere–warm, low-density air rising in thunderstorm updrafts was able to accelerate rapidly upwards to the top of the lower atmosphere, since the surrounding air was cooler and denser at high altitudes. These vigorous updrafts needed some twisting motion to get them spinning and create tornadoes. Very strong twisting forces were present Friday over the tornado outbreak area, thanks to upper-level jet stream winds that blew in excess of 115 mph. These winds changed speed and direction sharply with height,imparting a shearing motion on the atmosphere (wind shear), causing the air to spin. High instability and a high wind shear are the two key ingredients for tornado formation.

Here’s more from Masters on the record-setting storms:

A key ingredient for tornado formation is the presence of warm, moist air near the surface, which helps make the atmosphere unstable. On the day of the March 2, 2012 outbreak, record warm air surged northwards into the tornado formation region, setting or tying daily high temperature records at 28 airports in Louisiana, Arkansas, Mississippi, Alabama, Tennessee, Kentucky, and Georgia.

The March 2 – 3 tornado outbreak: one EF-4, 39 deaths

The violent tornado rampage killed 39 and injured hundreds more, wreaking property damage that will likely exceed $1 billion. Hardest hit were Kentucky and Southern Indiana, which suffered 21 and 13 dead, respectively. Three were killed in Ohio, and one each in Alabama and Georgia. The scale of the outbreak was enormous, with a preliminary total of 117 tornadoes touching down in eleven states, from southern Ohio to Northern Florida. The National Weather Service issued 297 tornado warnings and 388 severe thunderstorm warnings. At one point, 31 separate tornado warnings were in effect during the outbreak, and an area larger than Nebraska–81,000 square miles–received tornado warnings. Tornado watches were posted for 300,000 square miles–an area larger than Texas….

Incredibly fast-moving storms
The speed with which some of the storms moved was truly exceptional, thanks to jet stream winds of up to 115 mph that pushed the thunderstorms forward at amazing speeds. A number of the tornadoes ripped through Kentucky with forward speeds of 70 mph, and two tornado warnings in Central Kentucky were issued for parent thunderstorms that moved at 85 mph. NWS damage surveys have not yet determined if one of the tornadoes from the outbreak has beaten the record for the fastest moving tornado, the 73 mph forward speed of the great 1925 Tri-State Tornado, the deadliest U.S. tornado of all-time.

Largest 5-day and 2nd largest 2-day tornado outbreak for so early in the year?

The March 2 tornado outbreak spawned 107 tornadoes, according to preliminary reports as of 8 am EST March 5 from NOAA’s Storm Prediction Center. An additional 10 tornadoes (preliminary) touched down on March 3, in Florida and Georgia; 3 additional tornadoes touched down on March 1 (Wikipedia does a great job tallying the stats for this tornado outbreak.) These preliminary reports are typically over-counted by 15%, but a few delayed reports will likely come in, bringing the total number of tornadoes from the March 2 – 3 outbreak to 90 – 100, propelling it into second place for the largest two-day tornado outbreak so early in the year. The top five two-day tornado outbreaks for so early in the year, since record keeping began in 1950:

January 21 – 22, 1999: 129 tornadoes, 4 deaths
March 2 – 3, 2012: 117 tornadoes (preliminary), 39 deaths
February 5 – 6, 2008: 87 tornadoes, 57 deaths
February 28 – March 1, 1997: 60 tornadoes, 10 deaths
January 7 – 8, 2008: 56 tornadoes, 4 deaths

Though the 36 tornadoes that occurred during the February 28 – 29 Leap Day outbreak were part of a separate storm system, the five-day tornado total from February 28 – March 3, 2012 is likely to eclipse the late January 18 – 22, 1999 five-day tornado outbreak (131 tornadoes) as the most prolific five-day period of tornado activity on record for so early in the year.

And yes we need to improve housing for those in tornado alley.  That’s a great thing for blogs that don’t focus on climate to write about.  Just as obviously we need an aggressive strategy for reducing GHGs that also supports real adaptation.

You can donate to the American Red Cross disaster relief here.

BACKGROUND ON THE SCIENCE

For decades, scientists have predicted that if we kept pouring increasing amounts of heat-trapping greenhouse gases into the atmosphere, we would change the climate.   They specifically predicted that that many key aspects of the weather would become more extreme — more extreme heat waves, more intense droughts, and stronger deluges.

As far back as 1995, analysis by NOAA’s National Climatic Data Center (led by Tom Karl) showed that over the course of the 20th century, the United States had suffered a statistically significant increase in a variety of extreme weather events, the very ones you would expect from global warming, such as more “” and more intense “” precipitation. That analysis concluded the chances were only “5 to 10 percent” this increase was due to factors other than global warming, such as “natural climate variability.” And since 1995, the climate has gotten measurably more extreme.

Multiple scientific studies find that indeed the weather has become more extreme, as expected, and that it is extremely likely that humans are a contributing cause (see “Two seminal Nature papers join growing body of evidence that human emissions fuel extreme weather, flooding that harm humans and the environment” and links therein).

Beyond that, as Dr. Kevin Trenberth, former head of the Climate Analysis Section of the National Center for Atmospheric Research, explained here in 2010: “There is a systematic influence on all of these weather events now-a-days because of the fact that there is this extra water vapor lurking around in the atmosphere than there used to be say 30 years ago. It’s about a 4% extra amount, it invigorates the storms, it provides plenty of moisture for these storms.”  He told the NY Times, “It’s not the right question to ask if this storm or that storm is due to global warming, or is it natural variability. Nowadays, there’s always an element of both.”

Munich Re, one of the world’s leading reinsurers, issued a news release in 2010, “large number of weather extremes as strong indication of climate change,” which noted:

Munich Re’s natural catastrophe database, the most comprehensive of its kind in the world, shows a marked increase in the number of weather-related events. For instance, globally there has been a more than threefold increase in loss-related floods since 1980 and more than double the number of windstorm natural catastrophes, with particularly heavy losses as a result of Atlantic hurricanes.

The rise in natural catastrophe losses is primarily due to socio-economic factors. In many countries, populations are rising, and more and more people moving into exposed areas. At the same time, greater prosperity is leading to higher property values. Nevertheless, it would seem that the only plausible explanation for the rise in weather-related catastrophes is climate change. The view that weather extremes are more frequent and intense due to global warming coincides with the current state of scientific knowledge as set out in the Fourth IPCC Assessment Report.

Here is their data:

I have tended to focus on the extreme weather events for which the causal chain is clearest and which will do the most damage to the most people in the foreseeable future.  Dust-Bowlification is probably at the top of that list (see NCAR analysis warns we risk multiple, devastating global droughts even on moderate emissions path).

But tornadoes are among the most visibly and viscerally destructive events — though I do find it interesting how much media coverage these tornadoes have gotten compared to, say, Tennessee’s 1000-year deluge aka Nashville’s ‘Katrina’.   So it was inevitable that scientists would be asked the obvious question of whether recent remarkable outbreaks are connected to human-caused climate change — and they were indeed remarkable.

Many scientists have weighed in on the climate-tornado link.  Two of the people who have done more research and publication on extreme weather and climate change than most are Trenberth and Karl, now director of NCDC.  I emailed Karl for his thoughts and here is what he wrote me last year:

Best info we have on the relationship between a warmer world and severe convective storms that can produce tornadoes is in the 2008 Synthesis and Assessment Report of the US Global Change Research Program. Chapter three of that Weather and Climate Extremes Assessment indicates that several studies do show that environmental conditions favorable for convection are more likely with more greenhouse gases, but results are not conclusive.

We now have improved resolution models running at our Oak Ridge Supercomputer thanks to the Stimulus funding.  We may be  able to make more definitive statements (one way or the other) after these get analyzed over the next few years. Meanwhile, we know that La Nina years tend to have a greater chance of severe outbreaks.  So as usual, there are natural factors that have to be considered, and any human made factors would be confounded within these naturally occurring events making our attribution much more difficult.

Joe, what we can say with confidence is that heavy and extreme precipitation events often associated with thunderstorms and convection are increasing and have been linked to human induced changes in atmospheric composition.

You can find that 2008 Report here.  I wrote about it here (see Sorry, deniers & delayers, Even Bush Administration says human emissions are changing the climate).

Trenberth made clear to me a year ago in an extended interview that he was dismayed by the media coverage of extreme weather, especially extreme deluges, that made no mention whatsoever of global warming:

I find it systematically tends to get underplayed and it often gets underplayed by my fellow scientists. Because one of the opening statements, which I’m sure you’ve probably heard is “Well you can’t attribute a single event to climate change.” But there is a systematic influence on all of these weather events now-a-days because of the fact that there is this extra water vapor lurking around in the atmosphere than there used to be say 30 years ago. It’s about a 4% extra amount, it invigorates the storms, it provides plenty of moisture for these storms and it’s unfortunate that the public is not associating these with the fact that this is one manifestation of climate change. And the prospects are that these kinds of things will only get bigger and worse in the future.

I emailed Trenberth last year to check his quote in ThinkProgress. And I again checked with him yesterday. He stands by the quote with the clarification he had added of the context:

It is irresponsible not to mention climate change in stories that presume to say something about why all these storms and tornadoes are happening.

The environment in which all of these storms and the tornadoes are occurring has changed from human influences (global warming). Tornadoes come from thunderstorms in a wind shear environment. This occurs east of the Rockies more than anywhere else in the world. The wind shear is from southerly (SE, S or SW) flow from the Gulf overlaid by westerlies aloft that have come over the Rockies. That wind shear can be converted to rotation. The basic driver of thunderstorms is the instability in the atmosphere: warm moist air at low levels with drier air aloft. With global warming the low level air is warm and moister and there is more energy available to fuel all of these storms and increase the buoyancy of the air so that thunderstorms are strong. There is no clear research on changes in shear related to global warming. On average the low level air is 1 deg F and 4 percent moister than in the 1970s.

Just because attribution is difficult doesn’t mean that the subject of global warming should be avoided entirely when talking about tornadoes.  Equally important, when discussing extreme weather and climate, tornadoes should not be conflated with the other extreme weather events for which the connection is considerably more straightforward and better documented:

TP quotes climate scientist Gavin Schmidt, climate modeller at the NASA Goddard Institute for Space Studies, who said:

It is a truism to say that everything has been affected by climate change so far and therefore this latest outbreak must in some sense have been affected, but attribution is hard and the further down the chain the causality is supposed to go, the harder this is. For heat waves it is easier, for statistics on precipitation intensity it easier – there are multiple levels of good modelling, theory and observations to back it up. But we have much less to go on with tornadoes.

There are lots of posts from last year on this.  Stu Ostro, Weather Channel Senior Meteorologist, wrote in his May 2011 post, “The Katrina of tornado outbreaks“:

The atmosphere was explosively unstable with summerlike heat and humidity, interacting with a classic wind shear setup as a strong jet stream and upper-level trough crashed overhead”….

The atmosphere is extraordinarily complex, and ultimately what’s happened the past month is probably a combination of influences, including La Nina, other natural variability, and anthropogenic global warming.

Here is how meteorologist and former hurricane hunter Dr. Jeff Masters put it May 31, 2011:

In summary, this year’s incredibly violent tornado season is not part of a trend. It is either a fluke, the start of a new trend, or an early warning symptom that the climate is growing unstable and is transitioning to a new, higher energy state with the potential to create unprecedented weather and climate events. All are reasonable explanations, but we don’t have a long enough history of good tornado data to judge which is most likely to be correct.

Here is how Masters puts it today:

Last year’s tornado season was incredibly severe, and we are off to one of the worst early-season starts to tornado season on record now in 2012. However, it is too soon to ring the alarm bells on climate change being responsible for this. The tornado data base going back to 1950 doesn’t show an increasing trend in strong tornadoes in recent decades. While climate change could potentially lead to an increase in tornadoes, by increasing instability, it could also decrease them, by decreasing wind shear. I’d need to see a lot more bad tornado years before blaming climate change for the severe tornado seasons of the past two years. One thing that climate change may be doing, though, is shifting the season earlier in the year. The 5-day total of tornadoes from February 28 – March 3 will probably break the record of 131 set in 1999 for the largest tornado outbreak so early in the year. Warmer winters, and an earlier arrival of spring due to a warming climate, will allow tornado season to start earlier–and end earlier. This year’s early start to tornado season is consistent with what we would expect from a warming climate. I have a more extensive article on this subject that has just been published by Weatherwise magazine….

Michael Tobis pointed out Judith Curry’s post, which I wouldn’t normally link to given her general abandonment of science, but she pointed out the study I cited at the top, The Effect of Climate Change on Tornado Frequency and Magnitude:

A research project by Michael Pateman and Drew Vankat found that the frequency of tornadoes had increased between 1950 and 1999″”though better detection likely played a significant role in those statistics. But if there’s strong evidence that climate change and tornadoes are connected, researchers have yet to uncover it….

The researchers themselves found:

There is an obvious increase in tornado frequency between 1950-1999. This could be due to increased detection. Also this could be due to changing climatic conditions. Looking at the raw data we have seen that there are generally less tornadoes in El Nino years compared to La Nina Years. But, since we were unable to get climate data, we were unable to see if the change in the frequency was due to climate factors.

Our data has failed to show a strong correlation in increase in tornado frequency and magnitude during El Nino and La Nina events.

The jury is out.

For more data on the increase in frequency, which is certainly due in large part to better detection, here is NCDC’s State of the Climate:  Tornadoes Annual 2010:

A NYT blogger directed us to this chart:

There is no apparent trend in the strongest tornadoes (F5 is the most destructive).  The NYT blogger quotes Harold Brooks of the National Severe Storms Laboratory:

The primary changes appear to occur ~1975, most likely as a result of the retrospective rating process that assigned ratings to tornadoes prior to the near-real-time ratings that began when the [National Weather Service] adopted the F-scale operationally in the mid-1970s, and ~2000, for reasons that aren’t completely clear, but are likely due to an increased emphasis on examining construction details and policies that changed the nature in how the ratings are created for the strongest tornadoes. Both have lead to a decrease in probability of a tornado being very strong, given that it’s strong. It’s possible that there’s a meteorological component, but the reporting practice changes are large enough that I don’t think we can pull a physical signal out, even if it’s fairly large.

So it may simply be that the data is simply is too confused by the reporting practices for analysis to draw any strong conclusions.  That doesn’t mean the question shouldn’t be asked or that scientists shouldn’t give their best answer.

In general I do think it’s best to avoid statements like “global warming is to blame for” or “global warming caused” or “this is evidence of global warming,” especially in regards tornadoes.

Finally, while tornadoes will continue to grab the headlines wherever they flatten cities and take lives, it is virtually certain that other extreme events — and ultimately the permanently changed climate — will cause the greatest harm attributable to human emissions of greeenhouse gases.

The population hasn’t even acclimatized to the climate change we’ve had already — in part because the GOP and the fossil-fuel-funded disinformation campaign have obfuscated efforts to inform the public.

We’ve only warmed about a degree Fahrenheit in the past half-century.  If we keep listening to the disinformers, we are on track to warm nearly 10 times that this century (see M.I.T. doubles its 2095 warming projection to 10°F — with 866 ppm and Arctic warming of 20°F).  We ain’t seen nothing yet. Or, as one commenter put it:

“Mother nature is only warming up.”

Note: The NBC quote is by Tom Costello from the March 3, 2012 Evening News. Also, h/t Gail at Wit’s End

Related Posts:

• Climate Story of the Year: Warming-Driven Drought and Extreme Weather Emerge as Key Threat to Global Food Security
• A New Record: 14 U.S. Billion-Dollar Weather Disasters in 2011

• NOAA: Climate change “largely irreversible for 1000 years,” with permanent Dust Bowls in Southwest and around the globe.  This January 2009 PNAS paper finds “¦the climate change that is taking place because of increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop”….   Among illustrative irreversible impacts that should be expected if atmospheric carbon dioxide concentrations increase from current levels near 385 parts per million by volume (ppmv) to a peak of 450-600 ppmv over the coming century are irreversible dry-season rainfall reductions in several regions comparable to those of the “dust bowl” era

• Study: Global warming is driving increased frequency of extreme wet or dry summer weather in southeast, so droughts and deluges are likely to get worse

The number of people who believe that the planet is warming is at its highest level since the fall of 2009. According to a survey conducted in December 2011 by the National Survey of American Public Opinion on Climate Change, 62% of Americans say they think global warming is happening. That’s up 7% from last spring.

That matches other recent public opinion research Climate Progress has reported on (see “Gallup poll: Public understanding of global warming gains” and “Independents, Other Republicans Split With Tea-Party Extremists on Global Warming.”

Significantly, Americans are attributing their increased belief in global warming to their (correct) perception that the planet is warming and the weather is getting more extreme. Roughly half of people who believe in global warming said that these were the primary influence.

This is certainly understandable. On the one hand, the media and key opinion-makers have all but stopped talking about the subject, so it would be hard for people to be convinced by those two sources. On the other hand, it’s kind of hard to miss the extreme heat and uber-extreme weather events of the past two years.

With record-shattering droughts, floods and storms in 2011 that scientists attribute to an increasing degree to warming, atmospheric circulation changes, and extra moisture in the atmosphere driven by greenhouse gas emissions, and with 4 out of 5 Americans impacted by extreme weather since 2006, more people say that temperatures and weather changes are influencing their perception of global warming.

Even though extreme weather events are increasing in frequency and intensity, the close relationship between weather and beliefs about global warming can potentially make public opinion fickle over the short term — particularly since the continental United States comprises only a tiny fraction of the world and thus its weather is even more erratic than the Earth’s climate as a whole.

[As an aside, it isn't entirely clear to me that when people say they have "observed" warmer temperatures or weather changes, they only mean weather they personally observed locally -- as opposed to what they might have observed on TV or even heard from friends and relatives around the country -- JR.]

The Brookings Institution, which released a report on the poll, explains how the phenomenon can swing beliefs on the issue:

A sampling of the open-ended comments provided by survey respondents helps demonstrate the role that weather plays in shaping individual views on global warming. A male senior citizen from Illinois, who feels that there is solid evidence of global warming, said that the primary reason that led him to this conclusion was “winters just aren’t as cold as they were in the past.” Similarly, a middle-aged woman in Florida attributed her position on global warming primarily to her observations that “this time of year is warmer than it is expected to be.” A young man in Texas identified the primary reason for his view that the Earth is warming to “temperatures last summer that were awful,” while another young Texan stated that the “droughts this past summer” were the primary reason that she believed temperatures on earth were increasing. In these cases and many others Americans turn first to the weather they experience as the key reason for their acceptance of global warming.

Of those stating that they don’t think temperatures on earth are increasing, 1 in 3 cited observations of weather as the main cause. Again, the open-ended responses are illustrative of the effect that personal observations of weather have on views about climate change. A young New Jersey woman said “our weather seems just as cold as in the past,” while a middle-aged man in Minnesota noted that “we had more snow last year than ever.” A senior citizen from Ohio said that “winters were just as cold as when I was a kid,” and a young man from Maine simply said “that it’s freezing out” when asked what the primary factor was for his view that global warming was not occurring. As with those who believe global warming is happening, skeptics regularly turn to experience with weather to explain why they have arrived at their position on the matter.

A deeper look at regional differences illustrates this trend. The pollsters asked Americans in different regions of the U.S. about whether drought impacted their belief that the earth is warming. In the south, where states are dealing with an historic, crippling drought that has caused billions of dollars in damages to agriculture, people were far more likely to attribute the lack of rain to global warming:

Here’s another interesting example of the swings in perception, according to the poll: After the cold winter of 2010 and 2011, 40% of those who did not believe global warming said personal observations were their core reason. However, before the snowy winter started, only 30% of non-believers said personal observations were the reason.

That’s human nature. This poll suggests that the number of Americans who understand the climate is changing will likely increase with more extreme weather events as the problem gets worse — not simply because of increasing scientific evidence that tells us we should do something today.

It also tells us what other polls have demonstrated: Talking about global warming isn’t as touchy as politicians (notably our President) make it out to be. According to the data, 55% of Independents believe the earth is warming, while only 30% say it is not. Republicans are split down the middle, with 47% saying they believe in global warming and 42% saying they do not.

Related Story:

• Democrats Taking “Green” Positions on Climate Change “Won Much More Often” Than Those Remaining Silent

Figure 1. County-level map of federally-declared weather-related disasters between 2006 – 2011. Tornadoes and severe thunderstorms in the Midwest, and heavy rains and snows from Nor’easters, hurricanes, and other storms in the Northeast gave those two regions the most disaster declarations. An interactive version of this map that allows one to click and see the individual disasters by county is on the Environment America website.

by Jeff Masters, reposted from the WunderBlog

Since 2006 , federally declared weather-related disasters in the United States have affected counties housing 242 million people–or roughly four out of five Americans. That’s the remarkable finding of Environment America, who last week released a detailed report on extreme weather events in the U.S.

The report analyzed FEMA data to study the number of federally declared weather-related disasters. More than 15 million Americans live in counties that have averaged one or more weather-related disasters per year since the beginning of 2006. Ten U.S. counties–six in Oklahoma, two in Nebraska, and one each in Missouri and South Dakota–have each experienced ten or more declared weather-related disasters since 2006. South Carolina was the only state without a weather-related disaster since 2006.

The report did a nice job explaining the linkages between extreme weather events and climate change, and concluded, “The increasing evidence linking global warming to certain types of extreme weather events–underscored by the degree to which those events are already both a common and an extremely disruptive fact of life in the United States–suggests that the nation should take the steps needed now to prevent the worst impacts of global warming and to prepare for the changes that are inevitably coming down the road.”

Jeff Masters is co-founder of the Weather Underground. This piece was originally published at the WunderBlog.

AtmosNews takes a lighthearted look at an unexpected analogy, explaining why some people call carbon dioxide (and the other greenhouse gases) the steroids of the climate system. Statistics and extreme behavior are involved, whether we’re talking about baseball or Earth’s atmosphere. NCAR scientist Gerald “Jerry” Meehl explains why.

NCAR has puts it together an very informative website on global warming and extreme weather, which I highly recommend.

Related Post:

• PBS Covers Link Between 2011′s “Mind-Boggling” Extreme Weather and Global Warming: It’s Like “Being on Steroids”

The laws of physics demand that the huge amount of heat-trapping gases humans are pumping into the atmosphere must be significantly altering the fundamental large-scale circulation pattern of the atmosphere.

Stronger hurricanes, bigger floods, more intense heat waves, and sea level rise have been getting many of the headlines with regards to potential climate change impacts, but drought should be our main concern. Drought is capable of crashing a civilization.

by Christine Shearer, reposted from the Conducive Chronicle

If you are interested in weather, chances are you have visited Weather Underground and read the posts of its director of meteorology, Dr. Jeff Masters. The consistently reliable Masters has been a rare voice in helping make sense of, rather than cloud (zing!), the increasingly strange weather events hitting the planet.

Masters has studied weather both on the ground and in the air. He received his bachelors and masters degrees in meteorology from the University of Michigan, and then worked as a Miami-based flight meteorologist for the National Oceanic and Atmospheric Administration’s (NOAA) Hurricane Hunters team. It was there that Masters and his crew, having lost temporary control of their radar and thinking they were heading toward a mild twister, flew right into the eye of Hurricane Hugo — a category 5 storm and the most destructive of its time.

Masters later wrote of the event in “Hunting Hugo“: “I look out my window, and behold the eye of Hurricane Hugo in its full fury. It is awesome, terrifying, supernatural.”

Although two engines of the plane were damaged, the crew made it out, which Masters attributes to the navigating of the team, the strength of the P3 plane, and luck. Masters returned to Ann Arbor for his PhD at U-M in 1991, continuing his work on the more applied science of air pollution meteorology: “I had a lot of concerns back then about how human activities were harming the environment and people who rely on the environment for jobs or for a strong economy.” He studied smog, but his attention soon turned to the growing issue of climate change.

He also started an earlier version of Wunderground in 1991, before it went online as the first weather site in 1995. Today, Wunderground.com is fed by the world’s largest network of 17,000 individual weather stations, and is the second most visited weather site in the world.

Masters shared some of his thoughts on meteorology, the effect of increasing greenhouse gases on weather and weather cycles, and the future of the earth’s climate.

Christine Shearer: As far as I can tell, you are one of the few meteorologists that puts daily weather events in a historic context, and therefore really looks at averages and deviations from the average. Would that be a fair assessment of what you do?

Jeff Masters: I focus on current weather events that have a high impact on people or society, and put them in a historical context. If there is current research which is relevant, I will mention that, particularly if the weather event in question is unusual and fits in with the general predictions of climate change.

Christine Shearer: How did you get interested in weather?

Jeff Masters: Growing up in Michigan is enough to get anyone interested in weather! The Midwest U.S. has a lot of weather extremes. I had my own home weather station back in junior high school, and used to go out and take regular wind, snow depth, and precipitation measurements. I was interested in all Earth Sciences, and had my own telescope, microscope, and rock collection. Both my uncle and grandfather taught physics (one at Stanford, the other at Purdue), so I initially thought I should be a physicist. But once I got into college, I found my interest drawn more to meteorology.

Christine Shearer: Very interested in meteorology – you became part of NOAA’s Hurricane Hunters team and had some pretty close calls, which you’ve written about. Do you ever miss flying into hurricanes? It must be quite an experience.

Jeff Masters: It was a fantastic opportunity to get to experience the world’s greatest storms first-hand, but I did enough flying into storms to satisfy this curiosity. I do miss the camaraderie of the great people I worked with, but I don’t miss the flying. Those 10 – 12 hour flights were long, and being on the road so much was difficult.

Christine Shearer: You helped start the website Weather Underground – what made you and your colleagues start the site?

Jeff Masters: We launched the predecessor of the web site at the University of Michigan, as a text-only menu-based educational service called “um-weather” back in 1991, before the web. The um-weather program became the most popular service of any kind on the entire Internet between 1992 – 1993, according to Merit Networking, Inc., who ran the Internet backbone at that time. So, we knew we had a popular concept, and we applied for and got several NSF grants to expand the effort into K-12 schools. When the web was established in 1995, the University and NSF encouraged us to take the next step and start a business.

Christine Shearer: Did you or your colleagues call the site Weather Underground after the 1960s activist group of the same name?

Jeff Masters: The company that became The Weather Underground grew out of an educational weather project with the same name that began in the early 1990s. Since the educational weather project and the original radical group The Weather Underground both got their start at the University of Michigan, the professor that supervised the educational project (Perry Samson) thought it would be an amusing tongue-in-cheek name for our small weather project. When the project became an amazingly successful one, and was spun off into a business, the name Weather Underground was kept — perhaps unwisely!

Christine Shearer: Could you give us a bit of insight on how meteorologists make their assessments? Beyond technological improvements, have you noted techniques that meteorologists can do themselves that make for more accurate forecasts?

Jeff Masters: We rely heavily on computer models, but there is no substitute for looking at the raw radar, satellite, and station data oneself to make a forecast. A lot of forecasting is experience–if you’ve been doing it for many decades, then you tend to pick up on recurring patterns more easily.

Christine Shearer: How do you think about the relationship between climate, climate change, and daily weather?

Jeff Masters: Climate is what you expect; weather is what you get. I like to think of the weather as a game of dice. Mother Nature rolls the dice each day to determine the weather, and the rolls fall within the boundaries of what the climate will allow. The extreme events that happen at the boundaries of what are possible are what people tend to notice the most. When the climate changes, those boundaries change. Thus, the main way people will tend to notice climate change is through a change in the extreme events that occur at the boundaries of what is possible. If you want a longer explanation, think of the weather as a game of dice like craps or backgammon, where Mother Nature rolls two six-sided dice to decide the day’s weather. There are 36 possible combinations of the two dice, and rolls can range from two to twelve. Most often, an ordinary roll like six, seven, or eight comes up; seven is the most common, with a 6 in 36 probability. Rolls of six and eight are only slightly less common, coming up with a 5 in 36 probability. These rolls of the “weather dice” correspond to typical summer weather–high temperatures in the mid- to upper 70s on a nice summer day in New York City, for instance. It is much harder to roll an extreme event–snake eyes (corresponding to a record cold day, with a high near 65), or double sixes (a record warm day, with a high near 100.) These rolls only have a 1 in 36 chance of occurring–about 3%.

Now think about what happens if we take one of the six-sided “weather dice” and paint an extra spot on each side. The old die still rolls a one through six, but the new die now rolls a two through seven. The most likely roll increases to an eight, so we’ve shifted to a warmer climate, getting a typical summertime high of 78 degrees instead of 76. However, the increase in 78 degree days isn’t that noticeable, since we’ve only increased the likelihood of getting an eight on our “weather dice” from 5 in 36 to 6 in 36. But now look at what has happened to extreme events as a result of loading our “weather dice” in favor of higher rolls. Whereas before we had only a 3% chance of rolling an twelve on our “weather dice”–an extreme heat day of 100 degrees in New York City–we’ve now tripled these chances to almost 9%, since there are three possible combinations of the dice that total twelve or higher. Moreover, it is no longer possible to roll snake eyes, corresponding to a record cold day, but it is now possible to roll a 13–a previously unprecedented weather event. Temperatures higher than 106, New York City’s previous all-time high temperature, can now occur.

Christine Shearer: Despite these shifting parameters, many meteorologists do not consider climate change when offering their reports, even when it comes to events where it seems it would at least deserve a mention. Why do you think that is – is there something fundamentally different about how meteorologists and climatologists are trained?

Jeff Masters: TV meteorologists are not required to have training in climate change in order to get their AMS [American Meteorological Society] seal of approval, and most do not have any formal training in climate science. In a subject as complicated and politically charged as climate change, I would expect most of them would be reluctant to offer their views on the subject if they have little training.

Christine Shearer: A recent popular science magazine had an article stating that many experts so far attribute this year’s warm weather in the continental U.S. to La Niña and the effect of the Arctic and North Atlantic Oscillations on the jet stream, “not global warming.” But is there a case to be made that increasing greenhouse gases and their effects could be affecting pressure systems? What is your take on this year’s U.S. winter and what you have said is the most “unusual configuration” of the jet stream ever recorded?

Jeff Masters: The natural weather rhythms I’ve grown used to during my 30 years as a meteorologist have become disrupted over the past few years. Many of Earth’s major atmospheric circulation patterns have seen significant shifts and unprecedented behavior; new patterns that were unknown have emerged; extreme weather events were incredibly intense and numerous during 2010 – 2011. The laws of physics demand that the huge amount of heat-trapping gases humans are pumping into the atmosphere must be significantly altering the fundamental large-scale circulation pattern of the atmosphere. Unprecedented behavior like we’ve witnessed in the configuration of the winter jet stream over North America–with the four most extreme years since 1865 occurring since 2006–could very well be due to human-caused climate change. Something is definitely up with the weather, and it is clear to me that over the past two years, the climate has shifted to a new state capable of delivering rare and unprecedented weather events. Human emissions of heat-trapping gases like carbon dioxide are the most likely cause of such a shift in the climate.

Christine Shearer: Having really looked closely at the weather for a while now, is there something that stands out to you most?

Jeff Masters: The atmosphere I grew up with no longer exists. My new motto with regards to the weather is, “expect the unprecedented.”

Christine Shearer: Anything you would like to say?

Jeff Masters: Stronger hurricanes, bigger floods, more intense heat waves, and sea level rise have been getting many of the headlines with regards to potential climate change impacts, but drought should be our main concern. Drought is capable of crashing a civilization. To illustrate, drought has been implicated in the demise of the Mayan civilization in Mexico, the Anasazis of the Southwest U.S., and the Akkadians of Syria in 2200 B.C. The Russian heat wave and drought of 2010 led to a spike in global food prices that helped cause unrest in Africa and the Middle East that led to the overthrow of several governments. It’s likely that global-warming intensified droughts will cause far more serious impacts in the coming decades, and drought is capable of crashing our global civilization in a worst-case scenario, particularly if we do nothing to slow down emissions of carbon dioxide.

Extreme weather years like 2010 and 2011 are very likely to increase in frequency, since there is a delay of several decades between when we put heat-trapping gases into the atmosphere and when the climate fully responds. This is because Earth’s oceans take so long to heat up when extra heat is added to the atmosphere (think about how long it takes it takes for a lake to heat up during summer.) Due to this lag, we are just now experiencing the full effect of CO2 emitted by the late 1980s; since CO2 has been increasing by 1 – 3% per year since then, there is a lot more climate change “in the pipeline” we cannot avoid.

We’ve set in motion a dangerous boulder of climate change that is rolling downhill, and it is too late to avoid major damage when it hits full-force several decades from now. However, we can reduce the ultimate severity of the damage with strong and rapid action. A boulder rolling downhill can be deflected in its path more readily early in its course, before it gains too much momentum in its downward rush. For example, the International Energy Agency estimates that every dollar we invest in alternative energy before 2020 will save $4.30 later. There are many talented and dedicated people working very hard to deflect the downhill-rolling boulder of climate change–but they need a lot more help very soon.

JR: Meteorologist Dr. Jeff Masters said in June that, driven by global warming, “It Is Quite Possible That 2010 Was The Most Extreme Weather Year Globally Since 1816.″ In a late December PBS story on the link between 2011′s “mind-boggling” extreme weather and global warming, Masters said it’s like “being on steroids … for the atmosphere.” Now Masters examines “Where is the climate headed?”

by Jeff Masters, cross-posted from the WunderBlog

The year 2011 tied with 1997 as the 11th warmest year since records began in 1880, NOAA’s National Climatic Data Center said last week. NASA rated 2011 as the 9th warmest on record. Land temperatures were the 8th warmest on record, and ocean temperatures, the 11th warmest. For the Arctic, which has warmed about twice as much as the rest of the planet, 2011 was the warmest year on record (between 64°N and 90°N latitude.) The year 2011 was also the 2nd wettest year over land on record, as evidenced by some of the unprecedented flooding Earth witnessed. The wettest year over land was the previous year, 2010.

Figure 1. Departure of global temperature from average for 2011. The Arctic was the warmest region, relative to average. Image credit: NASA Earth Observatory.

How much of the warming in recent decades is due to natural causes?

The El Niño/La Niña cycle causes cyclical changes in global temperatures that average out to zero over the course of several decades. La Niña events bring a large amount of cold water to the surface in the equatorial Eastern Pacific, which cools global temperatures by up to 0.2°C. El Niño events have the opposite effect. The year 2011 was the warmest year on record when a La Niña event was present. Global temperatures were 0.12°C (0.2°F) cooler than the record warmest year for the planet (2010), and would very likely have been the warmest on record had an El Niño event been present instead.

Figure 2. Departure from average of annual global temperatures between 1950 – 2011, classified by phase of the El Niño-Southern Oscillation (ENSO). The year 2011 was the warmest year on record when a La Niña event was present. ENSO is a natural episodic fluctuation in sea surface temperature (El Niño/La Niña) and the air pressure of the overlying atmosphere (Southern Oscillation) across the equatorial Pacific Ocean. Over a period of months to a few years, ENSO fluctuates between warmer-than-average ocean surface waters (El Niño) and cooler-than-average ocean surface waters (La Niña) in that region. Image credit: National Climatic Data Center.

[JR:  See also It’s “Extremely Likely That at Least 74% of Observed Warming Since 1950″ Was Manmade; It’s Highly Likely All of It Was.]

Correcting for natural causes to find the human contribution
We know that natural episodes of global warming or cooling in the distant past have been caused by changes in sunlight and volcanic dust. So, it is good to remove these natural causes of global temperature change over the past 33 years we have satellite data, to see what the human influence might have been during that time span. The three major surface temperature data sets (NCDC, GISS, and HadCRU) all show global temperatures have warmed by 0.16 – 0.17°C (0.28 – 0.30°F) per decade since satellite measurements began in 1979. The two satellite-based data sets of the lower atmosphere (UAH and RSS) give slightly less warming, about 0.14 – 0.15°C (.25 – .27°F) per decade (keep in mind that satellite measurements of the lower atmosphere temperature are affected much more strongly by volcanic eruptions and the El Niño phenomena than are surface-based measurements taken by weather stations.) A 2011 paper published by Grant Foster and Stefan Rahmstorf, Global temperature evolution 1979 – 2010, took the five major global temperature data sets and adjusted them to remove the influences of natural variations in sunlight, volcanic dust, and the El Niño/La Niña cycle. The researchers found that adjusting for these natural effects did not change the observed trend in global temperatures, which remained between 0.14 – 0.17°C (0.25 – 0.31°F) per decade in all five data sets. The warmest years since 1979 were 2010 and 2009 in all five adjusted data sets. Since the known natural causes of global warming have little to do with the observed increase in global temperatures over the past 33 years, either human activity or some unknown natural source is responsible for the global warming during that time period.

Figure 3. Departure from average of annual global temperatures between 1979 – 2010, adjusted to remove natural variations due to fluctuations in the El Niño-Southern Oscillation (ENSO) cycle, dust from volcanic eruptions, and changes in sunlight. The five most frequently-cited global temperature records are presented: surface temperature estimates by NASA’s GISS, HadCRU from the UK, and NOAA’s NCDC, and satellite-based lower-atmosphere estimates from Remote Sensing Systems, Inc. (RSS) and the University of Alabama Huntsville (UAH.) Image credit Global temperature evolution 1979- 2010 by Grant Foster and Stefan Rahmstorf, Environ. Res. Lett. 6, 2011, 044022 doi:10.1088/1748-9326/6/4/044022.

Commentary: What do climate scientists think?
Some scientists have proposed that previously unknown natural causes could be responsible for global warming, such as a decrease in cloud-producing galactic cosmic rays. Others have proposed that the climate may be responding to the heat-trapping effects of carbon dioxide by producing more clouds, which reflect away sunlight and offset the added heat-trapping gases. These theories have little support among actively publishing climate scientists. Despite public belief that climate scientists are divided about the human contribution to our changing climate, polling data show high agreement among climate scientists that humans are significantly affecting the climate.

A 2008 poll of actively publishing climate scientists found that 97% said yes to the question, “Do you think human activity is a significant contributing factor in changing mean global temperatures?” In my personal experience interacting with climate scientists, I have found near-universal support for this position. For example, I am confident that all 23 climate scientists and meteorologists whom I am personally acquainted with at the University of Michigan’s Department of Atmospheric, Oceanic, and Space Science would agree that “human activity is a significant contributing factor in changing mean global temperatures.” It is good that we have scientists skeptical of the prevailing consensus challenging it, though, because that is how scientific progress is made. It may be that one of the scientists making these challenges will turn out to be the next Einstein or Galileo, and overthrow the conventional scientific wisdom on climate change. But Einsteins and Galileos don’t come along very often.

The history of science is littered with tens of thousands of discredited scientific papers that challenged the accepted scientific consensus and lost. If we rely on hopes that the next Einstein or Galileo will successfully overthrow the current scientific consensus on climate change, we are making a high-stakes, low-probability-of-success gamble on the future of civilization. The richest and most powerful corporations in world history, the oil companies, have spent hundreds of millions of dollars to push us to take this gamble, and their efforts have been very successful. Advertising works, particularly when your competition has little money to spend to oppose you.

Where is the climate headed?
The 2007 United Nations-sponsored IPCC report predicted that global temperatures between 2007 and 2030 should rise by an average of 0.2°C (0.36°F) per decade. The observed warming over the past 30 years is 15 – 30% below that (but within the range of uncertainty given by the 2007 IPCC climate models.) Most of the increase in global temperatures during the past 30 years occurred in the 1980s and 1990s. The 2000s have seen relatively flat temperatures, despite increasing CO2 emissions by humans. The lower-than-expected warming may be partially due to a sharp decrease in stratospheric water vapor that began after 2000. The missing heat may also be going into the deep ocean waters below about 1,000 feet (300 meters), as part of a decades-long cycle that will bring extra heat to the surface years from now.

Regardless, the laws of physics demand that the huge amount of heat-trapping gases humans are pumping into the atmosphere must be significantly altering the weather and climate, even if we are seeing a lower than predicted warming. As wunderground’s climate change blogger, Dr. Ricky Rood said in a recent post, Changing the Conversation: Extreme Weather and Climate: “Given that greenhouse gases are well-known to hold energy close to the Earth, those who deny a human-caused impact on weather need to pose a viable mechanism of how the Earth can hold in more energy and the weather not be changed. Think about it.”

Our recent unusual weather has made me think about this a lot. The natural weather rhythms I’ve grown to used to during my 30 years as a meteorologist have become significantly disrupted over the past few years. Many of Earth’s major atmospheric circulation patterns have seen significant shifts and unprecedented behavior; new patterns that were unknown have emerged, and extreme weather events were incredibly intense and numerous during 2010 – 2011.

It boggles my mind that in 2011, the U.S. saw 14 – 17 billion-dollar weather disasters, three of which matched or exceeded some of the most iconic and destructive weather events in U.S. history–the “Super” tornado outbreak of 1974, the Dust Bowl summer of 1936, and the great Mississippi River flood of 1927. I appeared on PBS News Hour on December 28 (video here) to argue that watching the weather over the past two years has been like watching a famous baseball hitter on steroids–an analogy used in the past by climate scientists Tony Broccoli and Jerry Meehl.

We’re used to seeing the slugger hit the ball out of the park, but not with the frequency he’s hitting them now that he’s on steroids. Moreover, some of the home runs now land way back in the seats where no one has ever been able to hit a home run before. We can’t say that any particular home run would not have occurred without the steroids, but the increase in home runs and the unprecedented ultra-long balls are highly suspicious. Similarly, Earth’s 0.6°C (1°F) warming and 4% increase in global water vapor since 1970 have created an atmosphere on steroids. A warmer atmosphere has more energy to power stronger storms, hotter heat waves, more intense droughts, and heavier flooding rains.

Natural weather patterns could have caused some of the extreme events we witnessed during 2010 – 2011, and these years likely would have been naturally extreme years even without climate change. But it strains the bounds of credulity that all of the extreme weather events–some of them 1-in-1000-year type events–could have occurred without a significant change to the base climate state. Mother Nature is now able to hit the ball out of the park more often, and with much more power, thanks to the extra energy global warming has put into the atmosphere.

Extreme weather years like 2010 and 2011 are very likely to increase in frequency, since there is a delay of several decades between when we put heat-trapping gases into the atmosphere and when the climate fully responds. This is because Earth’s oceans take so long to heat up when extra heat is added to the atmosphere (think about how long it takes it takes for a lake to heat up during summer.) Due to this lag, we are just now experiencing the full effect of CO2 emitted [by] the late 1980s; since CO2 has been increasing by 1 – 3% per year since then, there is a lot more climate change “in the pipeline” we cannot avoid.

We’ve set in motion a dangerous boulder of climate change that is rolling downhill, and it is too late to avoid major damage when it hits full-force several decades from now. However, we can reduce the ultimate severity of the damage with strong and rapid action. A boulder rolling downhill can be deflected in its path more readily early in its course, before it gains too much momentum in its downward rush. For example, the International Energy Agency estimates that every dollar we invest in alternative energy before 2020 will save $4.30 later. There are many talented and dedicated people working very hard to deflect the downhill-rolling boulder of climate change–but they need a lot more help very soon.

– Jeff Masters is co-founder of the Weather Underground. This piece was originally published at the WunderBlog.

Related Climate Progress Posts:

• We’ve only warmed about a degree and a half Fahrenheit in the past century.  We are on track to warm five times times that or more this century (see M.I.T. doubles its 2095 warming projection to 10°F — with 866 ppm and Arctic warming of 20°F ).
• In 2007, Science (subs. req’d) published research that “predicted a permanent drought by 2050 throughout the Southwest” — levels of aridity comparable to the 1930s Dust Bowl would stretch from Kansas to California.
• In October 2010, a National Center for Atmospheric Research (NCAR) study warned, “The United States and many other heavily populated countries face a growing threat of severe and prolonged drought in coming decades … possibly reaching a scale in some regions by the end of the century that has rarely, if ever, been observed in modern times.”

Seven countries and one territory set all-time hottest temperature records in 2011, and one nation set an all-time coldest temperature record. Image credit: Ilissa Ocko, Princeton University.

By Dr. Jeff Masters, in a Wunderblog repost

The year 2011 was the tenth warmest year on record for the globe, but the warmest year on record when a La Niña event was present (Ricky Rood has a discussion of this in his lastest post.) Seven nations and one territory broke all-time hottest temperature records. This is a far cry from 2010 (which tied for the warmest year on record), when twenty nations (plus one UK territory) set all-time hottest temperature records. One all-time coldest temperature record was set in 2011; this was the first time since 2009 one of these records was set. The all-time cold record occurred in Zambia, which ironically also set an all-time hottest temperature record in 2011. Here, then, are the most most notable extreme temperatures globally in 2011, courtesy of weather records researcher Maximiliano Herrera:

1. Hottest temperature in the world in 2011: 53.3°C (127.9°F) in Mitrabah, Kuwait, August 3
2. Coldest temperature in the world in 2011: -80.2°C (-112.4°F) at Dome Fuji, Antarctica, September 18
3. Hottest temperature in the Southern Hemisphere: 49.4°C (120.9°F) at Roebourne, Australia, on December 21
4. Coldest temperature in the Northern Hemisphere: -67.2°C (-89°F) at Summit, Greenland, March 18. This is also the coldest March temperature ever recorded in the Northern Hemisphere.
5. Hottest undisputed 24-hour minimum temperature in world history: A minimum temperature of 41.7°C (107°F) measured at Khasab Airport in Oman on June 27

New country hottest temperature records set in 2011

Iraq recorded its hottest temperature on record on August 3, 2011 in Tallil (Ali military airbase), when the mercury hit 53°C (127.4°F). The previous record was 52.3°C recorded at Diwanya FOB airbase a few days before.

Armenia recorded its hottest temperature on record on July 31 in Meghri, when the mercury hit 43.7°C (110.7°F). The previous record was 43.1°C in Meghri on July 17, 2005.

Iran recorded its hottest temperature in its history on July 28, 2011, when the mercury hit 53°C (127.4°F) at Dehloran. The previous previous record was set just one day earlier at Omidieh and Shoshtar, when the mercury hit 52.6°C (126.6°F). Older hotter temperatures have been measured in Iran using automated stations, but these temperatures have been found to be overestimated.

Kuwait recorded its hottest temperature on record on August 3, 2011, when the mercury hit 53.3°C (127.9°F) at Mitrabah. The previous record was 53.1°C in Sulaibiya on June 15, 2010. The Kuwait Meteorological Center confirmed the reading as authentic, though the temperature sensor had problems between 2009 and July 2010. Some temperatures as high as 53.5°C measured at the Kuwait City Airport during 2011 were in error. The 53.3°C (127.9°F) at Mitrabah thus represents:

1) The hottest temperature measured on Earth in 2011
2) New official national record for Kuwait
3) Second highest (undisputed) temperature ever recorded in Asia
4) Highest temperature ever recorded in an Arabic country
5) Third hottest location in the planet together with Lake Havasu City, AZ (after Death
Valley, CA and Moenjodaro, Pakistan)
6) A new world record for August

China broke its national heat record for both uninhabited and inhabited locations on July 14, 2011, when the temperature soared to 50.2°C (122.4°F) at a automatic station near Adyngkol Lake (just south of Turfan), and 49.4°C (120.9°F) at the town of Tuyoq. A higher reading of 50.7°C at Aydingkol Mirabilite on 23 July 1986 has not been verified as official by the Chinese.

Republic of the Congo set a new all-time extreme heat record on March 8, 2011, when the temperature hit 39.2°C (102.6°F) at M’Pouya. Congo’s previous all-time hottest temperature was 39.0°C (102.2°F) at Impfondo on May 14, 2005.

Zambia set an all-time national heat record of 109.0°F (42.8°C) at Mfuwe, on October 26, 2011, breaking the previous national record of 108.1°F (42.3°C) also set at Mfuwe, on November 17, 2010. A no longer functioning station at Lusitu, Zambia measured a higher temperature in November 1990, but surrounding stations were all about 10°C cooler, so the Lusitu 1990 reading is considered unreliable.

The French Southern and Antarctic Lands Territory tied its all-time hottest temperature record when Europa Island recorded 35.6°C (96.1°F) on November 12, 2011. The previous record was set at Juan de Nova Island on March 31, 1997.

New country coldest temperature records set in 2011
For the first time since 2009, a new national extreme cold temperature record was set. Zambia set an all-time national cold record of -9°C (16°F) at Choma on June 27, 2011, breaking the previous national record of -8°C (18°F), set on July 10, 1898, at Nalisa Western Province.

Special mention:
Russia had its hottest temperature on record at a regular synoptic reporting staion on July 30, 2011, when the mercury hit 44.3°C (111.7°F) at Divnoe in Russia’s Kalmykia Republic. Three hotter temperatures have been recorded at automated stations: 45.4°C in 2010 at a hydrological station at Utta, plus readings of 45°C at El’ton and 44.5°C at Verhjnky Baskunkak in August 1940.

Weather records researcher Maximiliano Herrera is the primary source of the weather records listed here and has worked tremendously hard to research them. He maintains a comprehensive list of extreme temperature records for every nation in the world on his website. If you reproduce this list of extremes, please cite Maximiliano Herrera as the primary source of the weather records.

Other posts looking back at the remarkable weather events of 2011
U.S. weather in 2011: unprecedented rains and wet/dry extremes
Top ten global weather events of 2011
2011: Year of the Tornado
Deadliest weather disaster of 2011: the East African drought
Tropical Storm Lee’s flood in Binghamton: was global warming the final straw?
Wettest year on record in Philadelphia; 2011 sets record for wet/dry extremes in U.S.
Hurricane Irene: New York City dodges a potential storm surge mega-disaster

– Dr. Jeff Masters, in a Wunderblog repost

Relate Climate Progress Post:

• PBS Covers Link Between 2011′s “Mind-Boggling” Extreme Weather and Global Warming: It’s Like “Being on Steroids”
• Hansen et al: “Extreme Heat Waves … in Texas and Oklahoma in 2011 and Moscow in 2010 Were ‘Caused’ by Global Warming”

“Climate dice,” describing the chance of unusually warm or cool seasons relative to climatology, have become progressively “loaded” in the past 30 years, coincident with rapid global warming.   The distribution of seasonal mean temperature anomalies has shifted toward higher temperatures and the range of anomalies has increased.  An important change is the emergence of a category of summertime extremely hot outliers, more than three standard deviations (σ) warmer than climatology.

This hot extreme, which covered much less than 1% of Earth’s surface in the period of climatology [1951-1980], now typically covers about 10% of the land area.  We conclude that extreme heat waves, such as that in Texas and Oklahoma in 2011 and Moscow in 2010, were “caused” by global warming, because their likelihood was negligible prior to the recent rapid global warming.