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Mann: We Must Heed James Hansen On Global Warming And Extreme Weather Since He’s Been Right For So Long

By Joe Romm and Climate Guest Contributor on August 9, 2012 at 12:25 pm

"Mann: We Must Heed James Hansen On Global Warming And Extreme Weather Since He’s Been Right For So Long"


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NASA’s James Hansen has been accurately warning about the dangers of global warming for more than three decades. In fact, 31 years ago this month, Hansen and six other NASA atmospheric physicists, published a seminal article in Science, “Climate Impact of Increasing Atmospheric Carbon Dioxide.”

The paper has a number of caveats, as befits a major projection before modern climate models and modern supercomputers were available, before we had decades of verifying observations, and before we knew just how fast greenhouse gas emissions would rise.

Yet the analysis bears up unbelievably well — any one of us would be delighted if we published something three decades ago that was this prescient:

The global temperature rose 0.2°C between the middle 1960s and 1980, yielding a warming of 0.4°C in the past century. This temperature increase is consistent with the calculated effect due to measured increases of atmospheric carbon dioxide. Variations of volcanic aerosols and possibly solar luminosity appear to be primary causes of observed fluctuations about the mean trend of increasing temperature. It is shown that the anthropogenic carbon dioxide warming should emerge from the noise level of natural climate variability by the end of the century, and there is a high probability of warming in the 1980s. Potential effects on climate in the 21st century include the creation of drought-prone regions in North America and central Asia as part of a shifting of climatic zones, erosion of the West Antarctic ice sheet with a consequent worldwide rise in sea level, and opening of the fabled Northwest Passage.

The 1980s warmed, manmade warming has emerged from the noise, the Northwest passage opened, the drought prone-regions have emerged, and sea level rise is a top worry, in part because of erosion of WAIS (see Nature 2012: Antarctica Is Melting From Below, Which ‘May Already Have Triggered A Period of Unstable Glacier Retreat’). That’s five for five.

In 1990, Hansen coauthored a more detailed warning on the future of warming-driven drought  in the Journal of Geophysical Research. It projected that drought would become increasingly common in the ensuing decades — another accurate prediction. The study warned that severe to extreme drought in the United States, then occurring every 20 years or so, could become an every-other-year phenomenon by mid-century. Many recent studies support that conclusion (see “James Hansen Is Correct About Catastrophic Projections For U.S. Drought If We Don’t Act Now“).

Now Hansen has published an analysis of how warming is driving the extreme weather we have been slammed by in recent years, including the off-the-charts heat waves and droughts (see Hansen: ‘Climate Change Is Here — And Worse Than We Thought’). The AP quoted a number of credible independent experts supporting Hansen’s analysis:

The science in Hansen’s study is excellent “and reframes the question,” said Andrew Weaver, a climate scientist at the University of Victoria in British Columbia….

Another upcoming study by Kevin Trenberth, climate analysis chief at the National Center for Atmospheric Research, links the 2010 Russian heat wave to global warming by looking at the underlying weather that caused the heat wave. He called Hansen’s paper an important one that helps communicate the problem….

White House science adviser John Holdren praised the paper’s findings in a statement: … “This work, which finds that extremely hot summers are over 10 times more common than they used to be, reinforces many other lines of evidence showing that climate change is occurring and that it is harmful.”

… Granger Morgan, head of engineering and public policy at Carnegie Mellon University, called Hansen’s study “an important next step in what I expect will be a growing set of statistically-based arguments.”

The NY Times article on Hansen’s study also quoted Weaver in support of the analysis, but managed to find some credentialed critics:

Martin P. Hoerling, a researcher with the National Oceanic and Atmospheric Administration who studies the causes of weather extremes, said he shared Dr. Hansen’s general concern about global warming. But he has in the past criticized Dr. Hansen for, in his view, exaggerating the connection between global warming and specific weather extremes. In an interview, he said he felt that Dr. Hansen had done so again.

Dr. Hoerling has published research suggesting that the 2010 Russian heat wave was largely a consequence of natural climate variability, and a forthcoming study he carried out on the Texas drought of 2011 also says natural factors were the main cause.

Dr. Hoerling contended that Dr. Hansen’s new paper confuses drought, caused primarily by a lack of rainfall, with heat waves.

“This isn’t a serious science paper,” Dr. Hoerling said. “It’s mainly about perception, as indicated by the paper’s title. Perception is not a science.”

Nonsense, literally.

Having reviewed the drought literature (and talked to leading drought experts) for my Nature piece, “The Next Dust Bowl,” I was able to show in May that Hoerling’s attacks on Hansen do not reflect the scientific literature and are incorrect.

Indeed, given that Hansen’s 1990 study was titled, “Potential evapotranspiration and the likelihood of future drought,” we know that he and the community of drought experts have long understood that drought conditions are driven by more than precipitation changes. The whole point of that paper was to examine the impact of warming-driven evaporation on soil moisture and drought. You can actually worsen droughts in semi-arid regions that don’t see a net precipitation change just from the heat drying out the soils.

Let me also add, separate from any argument that Hansen has made, that there is increasing evidence we are in the midst of a step function or quantum change in the climate because of Arctic warming (see Arctic Warming Favors Extreme, Prolonged Weather Events ‘Such As Drought, Flooding, Cold Spells And Heat Waves’). If this research holds up, then all analyses of current droughts based on precipitation trends that predate the massive loss of Arctic ice in the past few years may well ultimately be overturned.

In any case, Hansen has scientific “street cred” because he has been right for so long. I’ve written that we ignore him at our grave peril because Hansen’s mastery of climate science is quite literally what gives him climate prescience.

One of the country’s top climatologists, Michael Mann, makes the same point in a recent Daily Climate piece that I repost below in its entirety:

Opinion: Ignore climate Cassandra at our peril

James Hansen’s latest findings linking extreme weather to climate change is science society cannot afford to ignore.

by Michael Mann, via The Daily Climate

The first scientist to alert Americans to the prospect that human-caused climate change and global warming was already upon us was NASA climatologist James Hansen. In a sweltering Senate hall during the hot, dry summer of 1988, Hansen announced that “it is time to stop waffling…. The evidence is pretty strong that the [human-amplified] greenhouse effect is here.”

At the time, many scientists felt his announcement to be premature. I was among them.

I was a young graduate student researching the importance of natural – rather than human-caused – variations in temperature, and I felt that the “signal” of human-caused climate change had not yet emerged from the “noise” of natural, long-term climate variation. As I discuss in my book, The Hockey Stick and the Climate Wars, scientists by their very nature tend to be conservative, even reticent, when it comes to discussing findings and observations that lie at the forefront of our understanding and that aren’t yet part of the “accepted” body of scientific knowledge.

Dire warning

Hansen, it turns out, was right, and the critics were wrong. Rather than being reckless, as some of his critics charged, his announcement to the world proved to be prescient – and his critics were proven overly cautious.

Given the prescience of Hansen’s science, we would be unwise to ignore his latest, more dire warning.

In a paper published today in the prestigious journal Proceedings of the National Academy of Sciences, Hansen and two colleagues argue convincingly that climate change is now not only upon us, but in fact we are fully immersed in it. Much of the extreme weather we have witnessed in recent years almost certainly contains a human-induced component.

Hansen, in his latest paper, shows that the increase in probability of hot summers due to global warming is such that what was once considered an unusually hot summer has now become typical, and what was once considered typical will soon become a thing of the past – a summer too improbably cool to anymore expect.

We need to view this summer’s extreme weather in this wider context.

Not random

It is not simply a set of random events occurring in isolation, but part of a broader emerging pattern. We are seeing, in much of the extreme weather we are experiencing, the “loading of the weather dice.” Over the past decade, records for daily maximum high temperatures in the U.S. have been broken at twice the rate we would expect from chance alone. Think of this as rolling double sixes twice as often as you’d expect – something you would readily notice in a high stakes game of dice. Thus far this year, that ratio is close to 10 to 1.  That’s double sixes coming up ten times as often as you expect.

So the record-breaking heat this summer over so much of the United States, where records that have stood since the Dust Bowl years of the 1930s are now dropping like flies, isn’t just a fluke of nature; it is the loading of the weather dice playing out in real time.

The record heat – and the dry soils associated with it – played a role in the unprecedented forest fires that wrought death and destruction in Colorado and New Mexico. It played a role in the hot and bone-dry conditions over the nation’s breadbasket that has decimated U.S. agricultural yields. It played a role in the unprecedented 50 percent of the U.S. finding itself in extreme drought.

Other threats

Climate change is also threatening us in other ways of course, subjecting our coastal cities to increased erosion and inundation from rising sea level, and massive flooding events associated with an atmosphere that has warmed by nearly 2˚F, holding roughly 4 percent more water vapor than it used to – water vapor that is available to feed flooding rains when atmospheric conditions are right.

The state of Oklahoma became the hottest state ever with last summer’s record heat. It is sadly ironic that the state’s senior senator, Republican James Inhofe, has dismissed human-caused climate change as the “greatest hoax ever perpetrated on the American people.” Just last week he insisted that concern over the impacts of climate change has “completely collapsed.” This as Oklahoma City has just seen 18 days in a row over 100˚F (with more predicted to follow), Tulsa saw 112˚F Sunday, and 11 separate wildfires are burning in the state, with historic Route 66 and other state highways and interstates all closed.

The time for debate about the reality of human-caused climate change has now passed. We can have a good faith debate about how to deal with the problem – how to reduce future climate change and adapt to what is already upon us to reduce the risks that climate change poses to society. But we can no longer simply bury our heads in the sand.

Michael Mann is a widely renowned and much-vindicated climate scientist at Penn State University. This piece was originally published at The Daily Climate and was reprinted with permission.


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21 Responses to Mann: We Must Heed James Hansen On Global Warming And Extreme Weather Since He’s Been Right For So Long

  1. Spike says:

    Hansen states

    “In a new analysis of the past six decades of global temperatures, which will be published Monday, my colleagues and I have revealed a stunning increase in the frequency of extremely hot summers, with deeply troubling ramifications for not only our future but also for our present.”

    It’s plain to see the paper is an an analysis of measured temperatures over recent decades. I was shocked to read Hoerling’s rather dismissive suggestion that Hansen had confused heat with drought. One wonders what lies behind this.

    • I think we can qualify denial in various stages.

      1. Global warming isn’t happening (head in sand)
      2. Global warming is happening but it won’t be so bad (comfort zone)
      3. Global warming can’t be as bad as the numbers indicate (shock)
      4. I don’t believe it, it looks like science fiction (out of context shock)

      I think it’s safe to say that a number of scientists are in the second, third, and fourth categories.

      Hansen’s looking at the hard data and he’s telling the truth about what he sees. That’s why it’s so important to listen to him. He’s one of the few people who’ve managed to take themselves out of the picture and directly communicate what the science implies.

      The rest, well, they’re still struggling with how brutal the truth can be.

      • Buzz B says:

        You’re missing three more biggies:
        5. Global warming is happening but it’s all natural variability.
        6. Global warming is happening but it is going to be, on net, beneficial.
        7. Global warming is happening but there is nothing we can do about it (or it’s too expensive or hard to fix).

  2. prokaryotes says:

    Anybody who is still in denial should be forced to explain why. And then this argument shall be discussed and probably be debunked.

    Then we take our best risk management people from all branches of government and start with mandatory large scale action, to transition to a new economy, the clean industrial revolution 2.0

    But we have to leave the old path of fossil addiction, which includes geopolitical strategies and the warmongering, because we need these resources soon to combat climate change. And climate change will kill more people in a shorter time period than any war could do (maybe except for a global Nuclear War).

    The positive message is this, that oil firms can transition to generate renewables and weapon factories can be transformed to help stem all kind of new technologies on our way to a carbon negative future.

    But is must be clear that there is no future for a world where most people live in poverty. This just means, more birth rates and less technological advancements, which means fossil consumption and logging.

    Every single task must be weight in light of environmental footprints.

    We have to begin now, because we risk large climate feedbacks from thawing permafrost. This could mean abrupt outgassing of large quantities of methane. If we do not change the way we treat each other we will not make it, because we face a global phenomenon. And because otherwise we will just make war and then climate disruption will eventually tick civilization to collapse, everywhere.

    We require new thinking and the enemy is fossil combustion, Co2 emissions.

  3. john c. wilson says:

    Regarding that step change in bold text: If I understand Jennifer Francis’ work at all there is an observed high correlation between sea ice area and the amplitude of Rossby waves. And there is not a lot of time lag between new low ice area and observed effects on weather. We are only a few days away from a new record low for sea ice area. By mid-September the new low is going to be a large step change down. The presumed consequence should be even more extreme weather than 2012 without any remission. Please someone tell me I’m wrong.

    • John McCormick says:

      Phoenix is suffered through extreme temp highs.

      Today 113 °F
      Tomorrow 118
      Saturday 111
      Sunday 109
      Monday 109

      Extreme even for Phoenix.

  4. prokaryotes says:

    Dr. Kevin Trenberth: “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.” http://thinkprogress.org/climate/2012/06/27/507119/hell-and-high-water-strikes-media-miss-the-forest-for-the-burning-trees/

    Because of more water vapor around than in the past, there is more energy for weather phenomena, hence each single event is pushed by this type of “steroids”.

  5. Zimzone says:

    I’ve watched three ’500 year’ weather events occur up here in MN & ND in the past 2 years. The 2012 drought may well be the fourth.

    NOAA is going to have to find new language to describe what’s becoming far too common, yet Dr. Hansen continues to be a pariah to conservatives like Inhofe.

  6. M Tucker says:

    “The 1980s warmed, manmade warming has emerged from the noise, the Northwest passage opened, the drought prone-regions have emerged, and sea level rise is a top worry, in part because of erosion of WAIS. That’s five for five.”

    The science is crystal clear. The warming “has emerged from the noise.” From my days as an Army radio operator we would say, “I read you 5 by 5.” Inhofe and his ilk need to put on their headsets and get with the program! We are stalled. We huddle with great apprehension and fear behind a false wall of security provided by an economy that seems to continue on in spite of the attacks from drought and heat waves on our food and water supply. We are like soldiers of a great amphibious assault, stalled on the beach, sitting ducks to deadly fire from a completely disrupted and chaotic climate. We can stay on that beach behind that false wall of security and die or we can move inland to the true security provided by modern, 21st century, clean energy technology. I quote Colonel George Taylor who said on June 6, 1944 (you all know where that was), “There are only two kinds of people who are staying on this beach: those who are already dead and those that are gonna die. Now get off your butts…!” You hear me Inhofe and Ryan and Issa and Boehner and McConnell and all the others too afraid to cast off the false security of fossil fuel dependence!? Are you going to show some leadership and lead the way? Are you going to show some backbone and demonstrate what American excellence is truly all about? Or are you going to cower in fear and doom us all to misery and death?

    • prokaryotes says:

      RE GOP -> GOP Insider: How Religion Destroyed My Party
      In the new book, “The Party Is Over,” veteran Republican Mike Lofgren writes about the rise of politicized religious fundamentalism and how the GOP devolved into anti-intellectual nuts. http://www.alternet.org/news-amp-politics/gop-insider-how-religion-destroyed-my-party

      They should at least have the courage to prioritize on climate change, because it is a matter of patriotism, to defend our lands in it’s current state and preserve it for next generations. But all you get is recklessness… they act like Buck Turgidson.

      • Economic Democracy says:

        As bad as extremist Christian fundamentalism is, the biggest “religion” that has been destroying both parties and destroying the USA, but, yes, to an even more larger degree and to greater extremes transforming the Republican party is the Religion of “Free” (read: corporate-dictated and corporate centrally planned) “Free” Market Fundamentalist Economics

        • Spike says:

          Absolutely correct. I am re-reading Clive Hamilton’s great book, Requiem for a Species. He points out that that a projected delay of 13 months in reaching 2050′s projected GDP numbers has been enough for Homo economicus to sacrifice a stable climate.

  7. fj says:

    Eco-debt is a great concept!

    Monetary debt is vapid in comparison; as are the folks preaching austerity in the face of rapidly advancing environmental devastation; an emergency situation we must remedy at wartime speed.

    We are clueless as to how to produce the stuff that supports life on earth as it’s rapidly being depleted before our eyes.

  8. prokaryotes says:

    New focus in climate messages

    Experts tend to communicate climate change as either an environmental or a political issue but this approach has had limited impact on public concern. Other dimensions of climate change, such as public health and national security, could be used to engage the public. http://www.nature.com/nclimate/journal/v2/n8/full/nclimate1650.html

    • prokaryotes says:

      Psychology: Fear and hope in climate messages

      Scientists often expect fear of climate change and its impacts to motivate public support of climate policies. A study suggests that climate change deniers don’t respond to this, but that positive appeals can change their views. http://www.nature.com/nclimate/journal/v2/n8/full/nclimate1610.html

      I think of this in this way: More clean environment -> healthier/happier people -> more economical potential -> a better business environment (if all chains work sustainable).

  9. prokaryotes says:

    Increasing drought under global warming in observations and models Published online 05 August 2012 by Aiguo Dai http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate1633.html

    • prokaryotes says:

      I conclude that the observed global aridity changes up to 2010 are consistent with model predictions, which suggest severe and widespread droughts in the next 30–90 years over many land areas resulting from either decreased precipitation and/or increased evaporation.

  10. David F. says:

    I think one thing that’s sometimes lost on people is the sensitivity in the climate to a change in global temperature. We often hear about the sensitivity of the global temperature to CO2 emissions, but this doesn’t really tell us much about the climate. A one-degree temperature rise seems negligible. However, even a small rise like this can greatly affect the climate.

    As a case in point, see this graph from several years: http://scienceblogs.com/deltoid/wp-content/blogs.dir/443/files/2012/04/i-a2839c2cbd0cf4e7d39c9ccec500f917-hansen.png

    The graph was created to show Dr. Hansen’s projections from 1988 really weren’t too far off the mark. He had just used a slightly higher CO2 sensitivity than now thought likely. It was a response to Michael Crichton’s lies in State of Fear. But, I digress. What I really am trying to get at is that global temperatures are now as high as they were during the Altithermal (8-5 kya) and before that during the Eemian warm period (130-114 kya).

    During the Altithermal period, which is generally held to have been caused by Milankovitch Cycles, the American Midwest was a much drier and warmer place than it has been in the thousands of years since. On the other hand, other locations are thought to have been wetter during that period. So you can really see, looking back in the earth’s recent history, just how much of an effect even a small temperature change can bring. Of course, the LGM (25-15 kya) was only about 6C cooler than the recent past. And then much of the Northern Hemisphere was located under a mile or more of ice.

  11. Don says:

    Dr. Hansen was ahead of his time and on the mark. Whether one uses the GISS, NCDC, or HadCRUT datasets, the message is clear that the world is warming. The last cool monthly global land and sea anomaly occurred in February 1994 on GISS and February 1985 on the NCDC dataset. The last cool annual anomaly occurred in 1976 on both the GISS and NCDC datasets.

    The data are unambiguous and unanimous: the global climate has warmed.

    If the contrarians are to gain credibility they need to resolve a number of issues.

    1. They must find a new natural forcing or some combination of natural factors that allows them to recreate the climate record since the mid-20th century when the explanatory power of natural forcings declined. They need to find another variable or set of variables that allows them to explain the climate evolution at least as well as it is explained when anthropogenic forcings (CO2) are incorporated.

    2. They must find an explanation for the abrupt and dramatic reversal in the millennial scale decline in Arctic temperatures that was being driven by orbital forcings. As there is no evidence that the Atlantic Multidecadal Oscillation (AMO) has radically changed, the AMO cannot explain the dramatic shift that more than counters slowly declining summer solar insolation.

    3. They must find an explanation for the large expansion of extreme temperature anomalies (3σ or more) that has occurred in recent years. Such anomalies once covered an average of 0.1% to 0.2% of the globe during summers. They now cover around 10%. As synoptic patterns and oceanic cycles continue to play out as they have in the past, they need to explain why such expansive areas of extremes are only now occurring.

    To date, they have not done so. Rather, they have attacked the temperature record, arguing that the record has been “manipulated” to create the illusion of rising temperatures. Yet, if temperature adjustments were mainly the basis for the recorded rise in temperatures, one would find a relatively stable response from nature. Aside from declining summer sea ice extent in the Arctic, one finds a lengthening of growing seasons, northward shift in winter nesting ranges for birds, shortening duration of lake ice, and northward shift in plant hardiness zones, and general retreat of glaciers. The warming is real. It is not an artificial construct of temperature adjustments.

    Finally, there is a fingerprint of an ongoing energy imbalance that will continue to lead to additional warming. One finds a continuing increase in oceanic heat content (OHC), which shows up at the 0-700m and 0-2000m depths. The increase in OHC is consistent with greenhouse gas forcing.

    All said, AGW is real. It is ongoing. Dr. Hansen made the right call and arguably one of the great calls any scientist has ever made.

  12. Jim O' says:

    My Gawd! That’s what we say in Boston when we are wondering what planet some one just flew in from. This is from the National Snow and Ice Data Center Web Page:

    “Along with the substantial summer sea ice extent decline and the early Northern Hemisphere snow melt, the pace of Greenland surface melt suggests that 2012 is yet another interesting summer in the Arctic.”

    Are you f’g kidding me?! “another INTERESTING SUMMER IN THE ARCTIC”! Our scientific heroes stepping up to the plate big time!