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

Third least snowy winter on record for the contiguous U.S.

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.

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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”

“Likely …. the most prolific five-day period of tornado activity on record for so early in the year“

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:

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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:

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Climate Change Worsens Many of These Disasters

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.

Readers asked what a good extended metaphor was for global warming.  Here’s one, courtesy of the National Center for Atmospheric Research:

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”

An Interview with Weather Underground’s Dr. Jeff Masters

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.

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Next Up: The Droughts, Heat Waves, and Floods from the Last Two Decades’ Surge in CO2 Levels

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?

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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

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