Must-read Hansen and Sato paper: We are at a climate tipping point that, once crossed, enables multi-meter sea level rise this century

Climate change is likely to be the predominant scientific, economic, political and moral issue of the 21st century

Right now, we’re headed towards an ice-free planet.  That takes us through the Eemian interglacial period of about 130,000 years ago when sea levels were 15 to 20 feet higher, when temperatures had been thought to be about 1°C warmer than today.  Then we go back to the “early Pliocene, when sea level was about 25 m [82 feet] higher than today,” as NASA’s James Hansen and Makiko Sato explain in a new draft paper, “Paleoclimate Implications for Human-Made Climate Change.”

The question is how much warmer was it in the Eemian and early Pliocene than today — and how fast can the great ice sheets disintegrate?

We already know we’re at CO2 levels that risk catastrophe if they are sustained or exceeded for any extended period of time (see Science: CO2 levels haven’t been this high for 15 million years, when it was 5° to 10°F warmer and seas were 75 to 120 feet higher).

Hansen and Sato go further, saying we’re actually at or very near the highest temperatures of the current Holocene interglacial — the last 12,000 years of relatively stable climate that has made modern civilization possible.


They argue that the Eemian was warmer than the Holocene maximum by “at most by about 1°C, but probably by only several tenths of a degree Celsius.”  Their make the remarkable finding, that sea level rise will be highly nonlinear this century on our current business-as-usual [BAU] emissions that:

BAU scenarios result in global warming of the order of 3-6°C. It is this scenario for which we assert that multi-meter sea level rise on the century time scale are not only possible, but almost dead certain.

While this conclusion takes them well outside of every other recent prediction of sea level rise (SLR), Hansen deserves to be listened to because he has been right longer than almost anyone else in the field (see “Right for three decades: 1981 Hansen study finds warming trend that could raise sea levels“).   Also, at least one recent study that attempts to integrate a linear historically-based analysis with a rapid response term finds we are headed towards SLR of “as much as 1.9 metres (6ft 3in) by 2100” if we stay on BAU (see “Sea levels may rise 3 times faster than IPCC estimated, could hit 6 feet by 2100“).

Hansen and Sato make their case for a strong nonlinear SLR based on a “phase change feedback mechanism,” that, as we’ll see, appears consistent with the recent scientific literature and observations1:

There is a simple explanation for why the Eemian and Holsteinian were only marginally warmer than the Holocene and yet had (both) poles several degrees Celsius warmer. Earth at peak Holocene temperature is poised such that additional warming instigates large amplifying high-latitude feedbacks. Mechanisms on the verge of being instigated include loss of Arctic sea ice, shrinkage of the Greenland ice sheet, loss of Antarctic ice shelves, and shrinkage of the Antarctic ice sheets. These are not runaway feedbacks, but together they strongly amplify the impacts in polar regions of a positive (warming) climate forcing.

Augmentation of peak Holocene temperature by even 1°C would be sufficient to trigger powerful amplifying polar feedbacks, leading to a planet at least as warm as in the Eemian and Holsteinian periods, making ice sheet disintegration and large sea level rise inevitable.

Empirical evidence supporting these assertions abounds. Global temperature increased 0.5°C in the past three decades (Hansen et al., 2010) to a level comparable to the prior Holocene maximum, or a few tenths of a degree higher. Satellite observations reveal rapid reduction of Arctic sea ice (Stroeve et al., 2007) and surface melt on a large growing portion of the Greenland ice sheet (Steffen et al., 2004; Tedesco et al., 2011).

Arctic response to human-made climate forcing is more apparent than Antarctic change, because the response time is quicker due to the large proportion of land area and Greenland’s temperature, which allows a large expansion of the area with summer melting.

However, we must expect ice sheet mass balance changes will occur simultaneously in both hemispheres. Why? Because ice sheets in both hemispheres were in near-equilibrium with Holocene temperatures. That is probably why both Greenland and Antarctica began to shed ice in the past decade or so, because global temperature is just rising above the Holocene level.

Ice sheet disintegration in Antarctica depends on melting the underside of ice shelves as the ocean warms, a process well underway at the Pine Island glacier (Scott et al., 2009). The glacier’s grounding line has retreated inland by tens of kilometers (Jenkins et al., 2010) and thinning of the ice sheet has spread inland hundreds of kilometers (Wingham et al., 2009).

The article has a longer discussion of the ‘albedo flip’ underlying their conclusion:

Summer melting on lower reaches of the ice sheets and on ice shelves introduces the “albedo flip” mechanism (Hansen et al., 2007). This phase change of water causes a powerful local feedback, which, together with moderate global warming, can substantially increase the length of the melt season. Such increased summer melting has an immediate local temperature effect, and it also will affect sea level, on a time scale that is being debated, as discussed below.

We suggest that the warmest interglacials in the past 450,000 years were warm enough to bring the “albedo flip” phenomenon into play, while interglacials in the earlier part of the 800,000 year ice core record were too cool for surface melt on the Greenland and Antarctic ice sheets and ice shelves to be important. Increased surface melting, loss of ice shelves, and reduction of summer and autumn sea ice around the Antarctic and Greenland continents during the warmest interglacials would have a year-round effect on temperature, because the increased area of open water has its largest impact on surface air temperature in the cool seasons.

Further, we suggest that the stability of sea level during the Holocene is a consequence of the fact that global temperature remained just below the level required to initiate the “albedo flip” mechanism on Greenland and West Antarctica.

One implication of this interpretation is that the world today is on the verge of a level of global warming for which the equilibrium surface air temperature response on the ice sheets will exceed the global mean temperature increase by much more than a factor of two.

Coincidentally, a new article in Nature Geoscience, “Radiative forcing and albedo feedback from the Northern Hemisphere cryosphere between 1979 and 2008,” appears to lend support to this thesis.  After “synthesizing a variety of remote sensing and field measurements,” the authors find “the albedo feedback from the Northern Hemisphere cryosphere” is “substantially larger than comparable estimates obtained from 18 climate models.”  The news release notes:

A new analysis of the Northern Hemisphere’s “albedo feedback” over a 30-year period concludes that the region’s loss of reflectivity due to snow and sea ice decline is more than double what state-of-the-art climate models estimate.

The findings are important, researchers say, because they suggest that Arctic warming amplified by the loss of reflectivity could be even more significant than previously thought.

Also, the Hansen/Sato thesis seems consistent with a 2008 study in Geophysical Research Letters by leading tundra experts, “Accelerated Arctic land warming and permafrost degradation during rapid sea ice loss.” The lead author is David Lawrence of the National Center for Atmospheric Research (NCAR), who I have interviewed a number of times . The study’s ominous conclusion:

We find that simulated western Arctic land warming trends during rapid sea ice loss are 3.5 times greater than secular 21st century climate-change trends. The accelerated warming signal penetrates up to 1500 km inland”¦.

See also “What exactly is polar amplification and why does it matter?

Back to Hansen/Sato.  They have extended discussion of “linear versus non-linear ice sheet disintegration” and conclude:

The asymmetry of glacial-interglacial climate cycles, with rapid warming and sea level rise in the warming phase and a slower descent into ice ages, suggests that amplifying feedbacks can make the “wet” ice sheet disintegration process relatively rapid (Hansen et al., 2007). But how rapid?

Paleoclimate records include cases in which sea level rose several meters per century, even though known natural positive forcings are much smaller than the human-made forcing. This implies that ice sheet disintegration can be a highly nonlinear process.

We suggest that a nonlinear process spurred by an increasing forcing and amplifying feedbacks is better characterized by the doubling time for the rate of mass disintegration, rather than a linear rate of mass change. If the doubling time is as short as a decade, multi-meter sea level rise could occur this century. Observations of mass loss from Greenland and Antarctica are too brief for significant conclusions, but they are not inconsistent with a doubling time of a decade or less. The picture will become clearer as the measurement record lengthens.

What constraints or negative feedbacks might limit nonlinear growth of ice sheet mass loss? An ice sheet sitting primarily on land above sea level, such as most of Greenland, may be limited by the speed at which it can deliver ice to the ocean via outlet glaciers. But much of the West Antarctic ice sheet, resting on bedrock below sea level, is not so constrained.

And so they end their paper with this prediction and warning:

IPCC BAU (business-as-usual) scenarios assume that greenhouse gas emissions will continue to increase, with the nations of the world burning most of the fossil fuels including unconventional fossil fuels such as tar sands.
An alternative extreme, one that places a substantial rising price on carbon emissions, would have CO2 emissions beginning to decrease within less than a decade, as the world moves on energy systems beyond fossil fuels, leaving most of the remaining coal and unconventional fossil fuels in the ground. In this extreme scenario, let’s call it fossil fuel phase-out (FFPO), CO2 would rise above 400 ppm but begin a long decline by mid-century (Hansen et al., 2008).

The European Union 2°C scenario, call it EU2C, falls in between these two extremes.

BAU scenarios result in global warming of the order of 3-6°C. It is this scenario for which we assert that multi-meter sea level rise on the century time scale are not only possible, but almost dead certain. Such a huge rapidly increasing climate forcing dwarfs anything in the peleoclimate record. Antarctic ice shelves would disappear and the lower reaches of the Antarctic ice sheets would experience summer melt comparable to that on Greenland today.

The other extreme scenario, FFPO, does not eliminate the possibility of multi-meter sea level rise, but it leaves the time scale for ice sheet disintegration very uncertain, possibly very long. If the time scale is several centuries, then it may be possible to avoid large sea level rise by decreasing emissions fast enough to cause atmospheric greenhouse gases to decline in amount.

What about the intermediate scenario, EU2C? We have presented evidence in this paper that prior interglacial periods were less than 1°C warmer than the Holocene maximum. If we are correct in that conclusion, the EU2C scenario implies a sea level rise of many meters. It is difficult to predict a time scale for the sea level rise, but it would be dangerous and foolish to take such a global warming scenario as a goal.

If Hansen and Sato are right, we will know within a decade or two.  Unfortunately, continuing to do nothing while we wait to find out all but ensures we cross the tipping point and entire the realm of worst-case scenarios.  Further delay is beyond immoral.

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37 Responses to Must-read Hansen and Sato paper: We are at a climate tipping point that, once crossed, enables multi-meter sea level rise this century

  1. Steve Bloom says:

    Joe, note that the Flanner et al. numbers work out to the same forcing as 30 PPM CO2.

    Also, would it be possible for you to ask Hansen about the implications of Flanner et al.? Flanner himself was, um, reticent in the press release.

    [JR: Link?]

  2. WitsEnd says:

    To: “James Hansen”
    Date: Thursday, January 20, 2011, 7:47 AM

    “Climate change is likely to be the predominant scientific, economic, political and moral issue of the 21st century.”

    Actually, I disagree. The existential threat posed to humanity by climate change is going to be completely eclipsed by the collapse of the ecosystem, leading to mass starvation, well before the worst impacts of climate change are manifested.

    Consider this. Climate scientists use paleoclimatic data to compare the concentration of CO2 in the atmosphere to temperature. But, NEVER in the past have plants grown in an atmosphere with significant levels of caustic ozone, and that is what they are struggling to grow in now. There’s no way to go back in history and see how plants adapt to higher levels of ozone.

    And the answer is, they can’t, anymore than the corals and pteropods can adapt in a short period of time to ocean acidification. First the trees and long-lived species exposed to cumulative damage over years and decades showed signs of a mass die-off, and in just the past couple of years, annual plants have the same symptoms.

    Your own agency, NASA, estimates US agricultural yield losses in the billions annually. And as the background levels inexorably increase, so will the stunting of food crops. It’s been proven in scientific research that higher levels of ozone increase the virulence of disease, fungus and insects, and extreme weather.

    At the very least, climate models should be taking into account the loss of one of the most important CO2 sinks, trees. Our forests will be gone in the next few years if we continue in the collective delusion that we aren’t killing them with toxic emissions.

    I seriously suggest you take a little inventory. Pick a plot of ground, anywhere at all, and examine the trees. See how many have cracking, splitting bark, holes, and broken branches. Try to find a coniferous tree that has enough needles that you can’t see right through it to the other side. That’s not normal, it is indicative of impending death.



  3. Jeff Huggins says:

    “Further delay is beyond immoral.”


    A great book to read — I’m not finished yet, but it’s SUPER so far — is “Moral Ground: Ethical action for a planet in peril”, edited by Kathleen Dean Moore and Michael P. Nelson. Every climate and environmental activist should read this book and even carry it to meetings. Really.

    It contains short and compelling essays (and other materials) by all sorts of folks, including (just to name a few): E. O. Wilson, The Dalai Lama, the late Pope John Paul II, Bill McKibben, James Gustave Speth, Dale Jamieson, Thomas Friedman, Oren Lyons, James Garvey, Peter Singer, Bron Taylor, Wendell Berry, Thomas Berry, Brian Swimme, Paul Hawken, Barack Obama, and many many others. A super book.

    Be Well,


  4. Chlduvth70s says:

    The authors don’t appear to factor in the effect of possible methane release from beneath the East Siberian Ice Shelf and Northern Canada. Why do you think that is? It seems to me that a predictive model for climate change that doesn’t attempt to account for the potential release of methane will yield unrealistically optimistic forecasts.

  5. Leif says:

    A copy of this is being hand delivered to my local Paper Editors tomorrow.

  6. #Gail – what a superb letter to Hansen. Joe- thank you for posting.

    In one sense, Hansen is stuck by his science. His dire warnings are still very measured and careful. Paleo-humanity population was small and burned far less carbon than we do today.

    We are still under-evaluating our danger.

  7. James Newberry says:

    Hansen and Sato’s vital work, along with that of many other researchers (such as M. Pagani at Yale), indicates that even conventional climate change wisdom may be much too conservative. That is, the present international dialog about whether 50% or 80% reduction of GHG by 2050 is necessary, thereby implying a linear planetary response, is fundamentally incorrect.

    The climate response may be exponential. We find it hard to perceive because today’s response is that due to emissions up to several decades ago. With about half of total historic emissions having occured since about 1970, along with thermal inertia of geophysical response, we may be on the horizontal part of a curve going vertical.

    In that case, the phrase clear and present danger would be a vast understatement. Young people alive today may live to see the inundation of civilization’s great seaport cites and natural coastlines. Any human response would have to consider removing carbon “carbon negativity” while at the same time beginning ramp-down to industrial neutrality (of carbon). Starting now, starting yesterday, since we really do not know how this could be done without calamity.

    As youth say, dude are you kidding me? Good luck with that. What’s on the tube?

  8. Mel says:


    van Mantgem et. al. recently published a paper in Science (2009) that determined mortality rates in western North American forest have doubled in the last few decades – all elevations, all major species, all age categories – and they attribute this increase in mortality to climate change.

  9. K Nockels says:

    We are in the next decade, decade and a half at the most. about to be witness to the great unraveling of all the natural systems of this planet. We have not even considered at the political level anything above a 10% cut in CO2. If we do not start putting the ecology of this planet above the economy the converging crisis that is about to befall us will be massive in its impact on civilization.

  10. Lou Grinzo says:

    Recipe for toast: Us.

  11. Bob Lang says:

    James #7 Couldn’t agree more. According to the following paper, even Chu and Holdren are out to lunch.

    Here’s a quote from Anderson and Bows (2008), Phil. Trans. R. Soc. A 13 November 2008 vol. 366 no. 1882 3863-3882:

    “The analysis presented within this paper suggests that the rhetoric of 2°C is subverting a meaningful, open and empirically informed dialogue on climate change …

    The paper concludes that it is increasingly unlikely any global agreement will deliver the radical reversal in emission trends required for stabilization at 450 ppmv carbon dioxide equivalent (CO2e). Similarly, the current framing of climate change cannot be reconciled with the rates of mitigation necessary to stabilize at 550 ppmv CO2e and even an optimistic interpretation suggests stabilization much below 650 ppmv CO2e is improbable….

    Unless economic growth can be reconciled with unprecedented rates of decarbonization (in excess of 6% per year15), it is difficult to envisage anything other than a planned economic recession being compatible with stabilization at or below 650 ppmv CO2e.”

  12. Ominous Clouds Overhead says:

    Sometimes I wish I didn’t read this blog, it makes me want to drink – so far I haven’t started, but who knows, with news like this.

  13. Michael T. says:

    Here is a NASA GISS paper from Hogrefe et al. 2011 about ozone over the Northeast US:

    “An analysis of long-term regional-scale ozone simulations over the Northeastern United States: Variability and trends”

  14. I just read this paper this morning, and immediately understood it was an important piece. The moment I finished reading it I knew our “buffer” to avoid some of the more serious impacts of climate change is rapidly disappearing. If it’s not gone already.

    IPCC BAU scenario here we come.

    @ Wit’s End.

    I’m going to post your comments on my blog with permission. Truth spoken with passion.

  15. Barry says:

    Chlduvth70s (#4) : “The authors don’t appear to factor in the effect of possible methane release from beneath the East Siberian Ice Shelf and Northern Canada. Why do you think that is? It seems to me that a predictive model for climate change that doesn’t attempt to account for the potential release of methane will yield unrealistically optimistic forecasts.”

    My understanding is that Hansen and Sato aren’t using models to make these predictions. They are looking at the paleoclimate to see what it did in similar circumstances.

    If so, the methane feedbacks at the time were included in the way the planet reacted back then.

    That is the beauty of Hansen’s approach over the years: focus on what the earth did in the past in similar situations. Using the Earth rather than models is what has allowed Hansen to be more right for much longer than anyone else about what is happening.

  16. Barry says:

    The one certainty about how much CO2 humanity will pump into the air in the coming decades is that nobody has any idea.

    The climate is reacting much more like an aggressive drunkard than anyone expected. 2010 freaky weather has damaged and scared a lot of people. Clear signs of landscape level instability are emerging in ecosystems across the globe. Everyone can see the genie coming out of the bottle now.

    In the same way that the climate is being forced to change more rapidly than it has in the past…humanity too is entering a stage where it will be forced to change rapidly along with it — one way or the other.

    I think humanity is very unlikely to continue BAU anything, including fossil fuel burn rate. The old normalcy is going away fast.

    The question is whether we get our act together in time to manage the transition gracefully. I’m pretty hopeful we have it in us to turn the crisis around into an opportunity to work united towards a real, meaningful and profound goal. Humans can be very good at that once they see the urgency and path forward.

  17. Paulm says:

    I think we are on for a impressive ice sheet event before 2015′ certainly by 2020.

  18. Colorado Bob says:

    WASHINGTON — Now that the House of Representatives has voted to repeal the health care law, Republicans say they’re likely to move soon to another target — a rewrite of the Clean Air Act so that it can’t be used to fight climate change.

    Read more:

  19. forestecocide says:

    Thanks Mel. I am familiar with that paper – there is a link to it on my website. However, the fact is, that it’s just about impossible to find a tree species anywhere in the world that isn’t described as threatened by one thing or another, whether its climate change, or insects, or various diseases, or drought, or cankers or fungus. And I’m including young trees being grown in nurseries in pots, receiving ample water. My point is, there is a global trend and the only thing that explains a global trend is the composition of the atmosphere. Scientists and foresters who focus on specific local issues are missing the overall picture.

    Try googling any kind of tree you can think of and without much searching you will find some research or news report that it is dying.

  20. NikFromNYC says:

    How about the calm cool collected visage of actual single site thermometer records to sooth the soul?

  21. DavidCOG says:

    Joe, typo:

    > …and entire the realm of worst-case scenarios.


  22. J Bowers says:

    Re. 20 NikFromNYC

    We were coming out of the Maunder Minimum then, but there is no similar solar or volcanic forcing today or recently to explain any similar rise as seen in England at that time. Also, your graph only shows one location’s measurements from that time period plotted in the 1700s (central England), most of the rest starting later. It isn’t the season for cherry picking in England yet. Perhaps you could adjust the X axis of each graph so that they actually match, in case inexperienced viewers miss the disparity in timelines?

    400 years of sunspot observations…

  23. John McCormick says:

    RE # 11

    Bob Lang, thanks for the cite on the Anderson paper. A link to it is below for those who are interested. Says it all.

    John McCormick

  24. John McCormick says:

    RE # 15
    Barry your comment is intuitive. Thanks.

    Hansen and Sato’s paper included the following that affirms your comment:

    “Paleoclimate records include cases in which sea level rose several meters per century, ***even though known natural positive forcings are much smaller than the human-made forcing***. This implies that ice sheet disintegration can be a highly nonlinear process.”

    John McCormick

  25. Aaron Lewis says:

    Re 17: That is also my conclusion based on changes in atmospheric circulation, heat transport in the atmosphere as latent heat, heat transport into ice sheets via water falling through moulins, and changes in the strength ice as it warms.

  26. Ed Hummel says:

    I’m finding it very hard to not just through up my hands, forget about everything and just wait to die (I’m 63). As others have already noted, Hansen’s conclusions probably carry more weight than most simply because he’s been so consistently right by using paleo data to see what Earth has done in the past under similar situations. It seems that every new study he puts out shows that we are in a more precarious situation than previously thought just a few months ago. I’m coming to the conclusion that the faster than expected changes we are seeing are due to all positive feedbacks that are kicking in simply because we are changing the atmosphere at a pace only seen in Earth’s history when a cataclismic event such as an asteroid or comet impact occurred. I guess one could say that the human race and its global, industialized, consumer driven, civilization has achieved the status of the latest impact event to affect this planet. Geologically speaking we seem to be just at the point of impact if any future geologists are around to analyze the equivalent of a KT boundary (holocene-anthropocene boundary?). I really don’t know what to say or do any more, since the politics in this country and in most of the world are an increasingly impervious impediment to what has to be done. I really feel for my nephews and their children and all the other innocents out there who won’t know what hit them in the next few years and decades – if they last that long!

  27. Colorado Bob says:

    Fresh attacks on Hansen –

    NASA’s Hansen: Dictatorship can save the Earth
    The New American – James Heiser – ‎4 hours ago‎
    As the tortured science which is invoked to support the theory of anthropogenic climate change continues to lose its credibility in the eyes of the American …

  28. J Bowers says:

    Re. 27 Colorado Bob

    Already been going up against idiots trying to pull down climate science with it. Notice that none of the bloggers directly link to Hansen’s original piece. Here’s a direct link for anyone to check it out for themselves, China and the Barbarians Part 1:

    I came away feeling that not only is it nearly impossible to get effective legislation through Congress, but that the special interests can prevent implementation almost interminably. Democracy of the sort intended in 1776 probably could have dealt with climate change, but not the fossil-money-‘democracy’ that now rules the roost in Washington.

    Stop press: James Hansen tells us something we already know.

    His South China Morning Post op-ed:

    It’s worth pointing to the must read NAS study: RISING ABOVE THE GATHERING STORM, REVISITED. Sign up at left to download a free PDF version.

  29. John Mason says:

    Joe, thanks for linking to this. I’ve printed a hard copy to read this afternoon over a Guinness or two :)

    It’s a very powerful theme: the past is the key to the future and what has happened before can happen again given the correct set of circumstances. However, what is unique on this occasion is the deliberate combustion of countless gigatonnes of fossil carbon by one of the planet’s resident species. That’s a first in the 4.6 billion year history of the place. What an experiment to perform – what the hell were we thinking?

    Cheers – John

  30. Sasparilla says:

    #29 John Mason, well said, non intentional geo-engineering at its best.

  31. @mel

    Gail is not far off in insisting that people look at ozone. And it is only one chemical that is causing plant death.

    There is another that is emitted by commonly used asphalt. Check the trees around newly paved parking lots this coming summer.

  32. Gnobuddy says:

    @26, Ed Hummel says:

    I’m finding it very hard to not just through up my hands, forget about everything and just wait to die (I’m 63).
    Ed, may I recommend reading “The Power of Now” by Eckhart Tolle? The central idea of the book is that this one instant – the Now – is virtually always trouble free, and almost all our pain and suffering comes from either memories of the past, or anticipation of the future. Reading the book and adjusting my viewpoints toward its philosophy have helped me get through many difficult times, by focussing on the beauty of this tiny instant of time, the Now.

    You and I are both alive at this instant, and there have never been any guarantees of anything else. Let’s live life and enjoy this moment, which is all we ever really have. The future is nothing more than a guess, a figment of our imagination. I might die in 50 years of old age, or in 20 years as the ecosystem collapses, or in five years of a heart attack, or I might get terminal cancer next year, or I might be hit by a car and killed five minutes from now. I don’t know, and if I did, I hope I would still find the courage to enjoy my life while it lasted.

    Science and intellect both predict that almost certainly the future for a vast amount of life on this planet is bleak, yes, and there will be collective suffering and death. But, you know, where there is life there is *always* death. Every one of us humans, and every other living thing on planet earth, will die eventually. The only difference this time around is that lots of us will be dying together, and that is not so unusual either, as there have been great extinctions in the past.

    It has been obvious to me for years now that humankind cannot voluntarily change on the scale needed to avert global catastrophe, and therefore catastrophe is inevitable. This comes as a shock to us, since our brains are biologically wired to essentially make us believe that we will continue to live forever. But in fact death is certain for all of us, but that individual catastrophic future end need not keep us from being happy and living full lives in the Now.

    For the climate scientists who are still fighting to save people from themselves, a tip of my hat to you. Given the nature of the collective human psyche, you are doing thankless and inevitably futile work. Your warnings will not be sufficiently heeded, and your recommendations will not be sufficiently acted upon. But your courage and intelligence and labour is greatly appreciated, and your discoveries at least allow us to hold our heads high and face the facts with knowledge rather than ignorance. Nero may have had exactly the right idea, fiddling while Rome burned – he knew he couldn’t stop it, so he enjoyed the Now as much as he could in the face of certain disaster.

    And now I’m going off to get a nice early lunch, and then play my guitar and enjoy some music and the lovely sunshine we’re experiencing today. And I encourage you, Ed Hummel, and anyone else feeling depressed by the unending stream of bad news about the future of the ecosystem, to find something enjoyable to you, and go enjoy it. We’re not dead yet, and there are still first loves to be kissed, peanut-butter-and-jelly sandwiches to be enjoyed, spring flowers to be smelled, and beautiful songs to be sung.


  33. There are many reasons why James Hansen deserves to be the most respected climate change scientist. However such as the strange world of climate change science that even Hansen does not recognize that the greatest dangers to the survival of huge most climate change vulnerable human populations and of most if not all of humanity, is not slowly rising sea levels in the future. The catastrophe of the loss of the Arctic summer sea ice is to our food supply in all regions right now at today’s committed warming.

    The impact of global warming on agriculture is the number one tipping point but is the only one not recognized. We have to maintain the only climate that we know that can feed a human population of billions, which is much less than ten thousand years ago when agriculture dawned in several regions of the world due to an agriculturally kind global climate.

    Certainly sea level rise would cause a terrible increase in environmental refugees but there are no projections suggesting that sea level rise could wipe out huge regional populations, or civilization, or most of humanity. The other impacts of global climate disruption on human populations are dead certainties to bring these about if we don’t heed Hansen’s 2008 call to recognize today’s planetary emergency. The public are not going to be alarmed at the debate over the centimetres of sea level rise over the next few decades and the public is not being warned that their food security is on the line today.

    The other odd thing about the restricted focus on sea level rise is that it is not defined by the 1992 Framework Convention on Climate Change as an adverse climate change impact danger, while human population health and food security specifically are.

    Even James Hansen does not include in his dangerous metrics the multiple disastrous impacts on agriculture from global warming and climate disruption. It is surely intuitive that mid continental land heating, climate seasonal variation, plus increases in heat waves droughts heavy downpours and floods will render even the most productive lands unsuitable for agriculture. The computer models, that we do not need to identify these climate change dangers, are very slowly confirming this. Even though the models still do not capture at least half of the adverse impacts the models put agriculture in all regions in decline above 3°C (IPCC AR4 2007). The climate food security assessment however ignores the loss of the summer Arctic ice ‘air conditioner’ effect to the entire northern hemisphere which would put the great agricultural regions of the northern hemisphere in peril. That alone would deprive people of food security in all regions.

    The other catastrophe to all life on Earth from the loss of the Arctic summer sea ice is the carbon feedback emissions from peat lands, thawing permafrost and ‘melting’ subsea Arctic methane hydrates. These cascading carbon feedbacks amplified by loss of albedo are absent from this year’s Hansen and Sato paper which is odd because they were in the Hansen albedo flip planet ‘in imminent peril’ 2007 paper. The loss of Arctic summer albedo would, as Hansen said in the 2007 paper, unleash a ‘cataclysm’. The cataclysm we need to fear most is from the combined force of Arctic methane carbon feedbacks and they are all operant today.

    If and when the seas threaten to rise over our coastal cities I am afraid their populations will be long gone. The global food security climate change emergency is today.

  34. Jack P. says:

    Thank you, thank you for this posting; big thanks also to the people who responded so intelligently and thoughtfully. Living among so many “flat-earthers” who still question whether climate change is even happening, I’m delighted to know there are good minds and hearts at work on this.

    As a youth I witnessed one violent act of mass deforestation, and it taught me forever the value of planting trees. I’ve recently moved to a new community that sits treeless and in seeming ignorance; I’m planting trees there as quickly as I can on the land I own.

    Clearly there’s a global need to change our BAU mindset and change it fast. I believe we all know, however, that it’s not likely to happen quickly unless we start seeing natural disruption on an even more ominous scale than we have to date. Planting new trees would not only buy us time that we otherwise would not get, but apparently is even more necessary than I knew. I have not heard of such steep declines in old-growth forest health across the globe. (Deforestation, yes; dying of protected/unexploited forests, no.)

    Can anyone talk a bit about the ozone problem? Is this an issue of the loss of the outer ozone, or are plants facing problems more as a result of ground-level ozone? I know trees and urban pollution can exacerbate ground-level ozone. Is there anything natural that consumes low-level ozone — or boosts upper-atmospheric ozone?

    Thank you so much for this discussion. Passing this one on to those I love and respect.


  35. iceman says:

    As John McCormick (#24) points out, nonlinearity is the crucial issue here. Hansen and colleagues helped bring the concept of “albedo flip” into mainstream thinking in a 2007 paper – notably, before the big Arctic ice melt-back that year. So his analysis of doubling time for ice loss merits close consideration. Two recent developments indicate that he is on target.
    In the Arctic, the updated GRACE data for Greenland ice mass shows that the downward arc of Fig.8(a) continues. (see
    – note that this graph has a different zero point on the vertical axis). The last low data point could be anomalous because of the enormous ice island that broke off the Petermann glacier. On the other hand, excess heat from the late-season 2010 open water in the eastern Baffin Bay could lead to an early melt onset in 2011.
    At the other pole, we have unusually rapid sea ice melt in the Antarctic early summer: see
    The first-year ice in the Ross Sea disappeared quickly, despite relatively cool temperatures recently. This points to ocean heat as the culprit, as Joe called out in an earlier post:
    The location and timing of the melt means even more summer sun heating the Antarctic Circumpolar Current “upstream” of the Western Antarctic Peninsula. So Paulm’s (#17) prediction of an “impressive ice sheet event” could well be realized in the West Antarctic region.

  36. Gnobuddy says:

    @26, Ed Hummel says:

    I guess one could say that the human race and its global, industialized, consumer driven, civilization has achieved the status of the latest impact event to affect this planet. Geologically speaking we seem to be just at the point of impact if any future geologists are around to analyze the equivalent of a KT boundary (holocene-anthropocene boundary?).
    There was a really interesting post on this website ( a while ago that compared the current excess solar thermal forcing (due to our greenhouse gas emissions) with the energy from the asteroid impact that wiped out the dinosaurs (and a lot of other lifeforms). The rough order-of-magnitude calculation came to the conclusion that over one century or so, the current level of thermal forcing would put the same energy into the earths atmosphere as that asteroid impact.

    If that calculation turns out to be right, it lines up almost exactly with what you (Ed Hummel) said. And, with all this climate change science going on, it is the clearest example of seeing the forest without being distracted by all the trees that I’ve seen yet. We may never figure out all the fine details of the thousands of coupled partial differential equations involved in a complete climate model, and politicians and other retards can argue about the details till the end, but it would take extraordinary stupidity to ignore the knowledge that we’re dealing with something with as big an impact as the asteroid that wiped the dinosaurs off this planet.

    I haven’t seen anyone else revisit this idea and do an independent estimate of the energies involved, and I’d really like to see that.


    P.S. I found the original post: it’s post #109, by FedUpWithDenial, in this thread:

    It’s a long post, but here’s the most relevant snippet:

    “It follows that over the course of a century one hundred billion tons (100 Gt) of man-made CO2 (a fraction of the current anthropogenic total) adds at minimum the heat equivalent of one hundred trillion tons (100 Tt) of TNT to the climate system, comparable to the energy yield of roughly 100,000,000 tons of a nuclear explosive such as Uranium-235. This is approximately the energy released by the prehistoric K-T impact which triggered the dinosaur extinction at the end of the Cretaceous Period.”

  37. Marc A says:

    I’m working through this paper and trying to follow the science as a layman. Overall it’s going well, but after 2 passes I’m still having trouble with one point in section 3, Fast-Feedback Climate Sensitivity (p. 5).

    It’s this: “Any planetary energy imbalance was at most a small fraction of 1 W/m2, as shown by considering the contrary: an imbalance approaching 1 W/m2 would be sufficient to melt all ice on Earth or change ocean temperature a large amount…”

    How do we know that a 1 W/m2 imbalance would do that?