Must-See Hansen and Caldeira on Sensitivity: Paleoclimate Record Points Toward Potential Rapid Climate Changes

Amounts of warming previously thought to be safe may instead trigger widespread melting of the world’s ice sheets and other catastrophic impacts, scientists said….

There’s evidence that climate sensitivity may be quite a bit higher than what the models are suggesting,” said Ken Caldeira, a senior scientist at Stanford University’s Carnegie Institution for Science.

That’s from a Daily Climate piece on this panel discussion at last weeks AGU meeting:

The sensitivity issue is a complicated one, as I’ve discussed.  The AGU discussion certainly helps clarify key issues and suggests that some effort is being put into a reconciliation of the different ways of  calculating.

Don’t miss the back and forth on whether we are headed toward 25 meters of sea level rise or 70 meters at the end.  For some of the science, 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 — “We have shown that this dramatic rise in sea level is associated with an increase in CO2 levels of about 100 ppm”.

If you’re interested on Caldeira’s work on a very high sensitivity —  5.5°C to 8°C (10 to 14 F) — click here.  It is based on the PETM 55 million years ago and “having strong functioning methane feedbacks.” Thankfully we’ve got nothing to worry about in the Anthropocene (see”NSIDC : Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100).

Here’s more of the Daily Climate piece:

Accelerating melting on the world’s ice sheets and other new observations have scientists concluding that even a two-degree Celsius rise in temperatures – a benchmark long seen as safe in global climate talks and other emissions reductions scenarios – could lead to an 80-foot rise in sea levels.

“The dangerous level of global warming is less than what we thought a few years ago,” said James Hansen, director of NASA Goddard Institute for Space Studies. “It was natural to think that a few degrees wasn’t so bad…. (But) a target of two degrees is actually a prescription for long-term disaster.”

Antarctica and Greenland are losing ice at a surprising clip, Hansen said, and methane hydrates – a potent source of greenhouse gas frozen beneath the seas – are starting to bubble up.

The key question for climatologists: How sensitive is the climate to increasing amounts of fossil fuel emissions. Last year humanity pumped almost 10 billion tons of carbon dioxide into the atmosphere, a half-billion tons more than 2009 and the largest jump in any year since the Industrial Revolution, according to the Global Carbon Project.

See also Biggest Jump Ever in Global Warming Pollution in 2010, Chinese CO2 Emissions Now Exceed U.S.’s By 50%.

The problem, those researchers said, is the “hang time” for carbon dioxide in the atmosphere. Even if greenhouse gas emissions stopped tomorrow, “climatically important” amounts of carbon dioxide and other compounds emitted today would continue to influence the atmosphere for thousands of years, Caldeira said.

See also Fossil CO2 impacts will outlast Stonehenge and nuclear waste

That kind of pressure, or “forcing,” on the atmosphere could be devastating, he cautioned.

About 55 million years ago a tremendous amount of methane was released into the atmosphere over a period of about 1 million years, and the planet heated by five degrees to eight degrees Celsius, or 10 degrees to 14 degrees Fahrenheit. The result was an ice-free planet with sea levels 230 feet higher than they are today.

In the eons since, carbon dioxide levels dropped and the ice reformed. But humanity’s emissions have the potential to send the globe back to those conditions, Caldeira and Hansen said.

“If you doubled CO2, which practically all governments assume we’re going to do, that would eventually get us to the ice-free state,” Hansen said.

Scientists don’t expect that ice to melt quickly. Assuming the current accelerated melting continues on the world’s ice sheets and glaciers, various climate models predict the ocean would rise between 1.5 feet and 2.3 feet by century’s end, said Tad Pfeffer, a glaciologist with the University of Colorado.

But the ice melted with atmospheric carbon dioxide levels at about 1,000 parts per million, Caldeira said. And he suspects that even 750 ppm, or about double today’s levels, could send the globe spiraling toward an ice-free state. Current emissions trends suggest the globe could reach that by the end of the century.

“We can’t double CO2,” Hansen added. “We would be sending our climate back to a state we haven’t adjusted to as a species.”

The time to act was a while ago, but now is much, much better than later.

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40 Responses to Must-See Hansen and Caldeira on Sensitivity: Paleoclimate Record Points Toward Potential Rapid Climate Changes

  1. Rabid Doomsayer says:

    So climate sensitivity on an upswing in temperature is different to sensitivity in a downswing.

    Looking at the temperature graphs for the ice ages, what a surprise. (or maybe not)

    On the subject of methane feedbacks

  2. Solar Jim says:

    RE: “pumped 10 billion tons of carbon dioxide” appears to be a misstatement.

    I believe this should be “carbon” instead, which would oxidize to just under 37 billion tons carbon dioxide per year.

    Either way, Mother Nature is “getting crushed,” and it may actually be clathrate methane that delivers the most forceful catalyst for abrupt climate destabilization.

  3. Joe Romm says:

    Good catch.

  4. scas says:

    “Rapid rise in Arctic methane shocks scientists – ‘Some plumes are 1 kilometer or more wide”

    “Earlier, we found torch-like structures like this but they were only tens of metres in diameter. This is the first time that we’ve found continuous, powerful and impressive seeping structures, more than 1000m in diameter. It’s amazing,” Semiletov said. “I was most impressed by the sheer scale and high density of the plumes. Over a relatively small area, we found more than 100 but, over a wider area, there should be thousands.”

  5. Lewis Cleverdon says:

    Given that we have at least six out of seven interactive feedbacks already accelerating with around 0.7C of AGW,
    and that we cannot expect them to subside until airborne CO2e is greatly diminished (either naturally or via managed Carbon Recovery techniques)
    why is there any discussion of what amount of warming greater than 0.7C is ‘dangerous’?

    0.7C is patently bluddy dangerous in that it is more than most of the feedbacks needed to start accelerating towards an uninhabitable planet.

    The idea of waiting till 2050 for anthro-emissions cuts, and then for them to take effect after the usual 35-yr timelag: i.e. in 2085, is just wrong in principle. The feedbacks are responding to the warming we have now – of which there is at least 35 yrs more in the pipeline, plus warming from our ‘tailing-off’ GHG outputs, plus a further doubling due to the loss of the sulphate parasol. Those who assert that another ~75yrs of additional warming won’t be enough to push the feedbacks beyond any human control need to explain their reasoning.

    We certainly need to end anthro GHG outputs ASAP, but that cannot and will not halt the feedbacks’ continued acceleration. GHG cuts are thus necessary but not sufficient to resolve our predicament.

    To achieve the feedbacks’ deceleration, both Carbon Recovery and Albedo Restoration techniques are indispensable. It is time this was acknowledged by all who take the threat of climate destabilization seriously.

    To ensure that appropriate objectives and techniques are applied, the first requirement is logically the establishment of a UN scientific supervisory body to concert, mandate and oversee RD&D efforts.



  6. Peter Mizla says:

    Aradhna Tripati, a UCLA assistant professor in the department of Earth and space sciences and the department of atmospheric and oceanic sciences 2 years ago came up with this research.

    You would have to go back at least 15 million years to find carbon dioxide levels on Earth as high as they are today, a UCLA scientist and colleagues report Oct. 8 in the online edition of the journal Science.

    “The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland,

  7. ryan says:

    Persistent drought in Romania threatens Danube’s power

    Scotland storm: Engineers battling to restore power

    UPDATE 1-UK power, gas prices rise on N.Sea outage, storm

    “To ensure that appropriate objectives and techniques are applied, the first requirement is logically the establishment of a UN scientific supervisory body to concert, mandate and oversee RD&D efforts.”

    waiting for the UN to act on this is nuts. the compounding effects of economic downturn and environmental catastrophes will destabilize global government and the entire industrial system beyond its capacity to act or control the riots, revolutions, and diasporas of the next few years/decade.

    people will have to adjust to disaster mode and devote their energy to survival/local resources/emergency response on their own.

  8. Colorado Bob says:

    An ashy pallor has spread across South Florida’s coral reefs over the past few months, as stressed corals expelled the algae that gives them color.

    The worst case of coral bleaching since surveys began in 2005 struck reefs from the Florida Keys through Martin County, harming the base of the region’s most biologically productive and economically important marine ecosystem.

    A survey coordinated by The Nature Conservancy, involving 13 dive teams from government agencies, universities and non-profit groups, found that 21 to 50 percent of colonies checked in the Keys, Broward County, Biscayne Bay and Martin County had bleached or turned pale. Palm Beach County saw less bleaching, with three to 6 percent of colonies affected.

    “It’s really widespread,” said James Byrne, Marine Science Program Manager for The Nature Conservancy. “We’ve seen it in past years in one or two areas, but we’ve never seen it across the whole reef.”,0,2186829.story

  9. Colorado Bob says:

    “Weather bomb” causes chaos, destruction across New Zealand
    The statement said the Nelson Region had been “heavily hit by a weather bomb with rainfall of up to 320mm in a 24 hour period”.

    The rainfall was heaviest in Takaka township which had record levels of rain. Around 510mm was recorded there over 48 hours, with 423mm of that falling over a 24 hour period, breaking a 35-year record for the area.

  10. Rabid Doomsayer says:

    What happens when we run out of fossil fuels and the Sky begins to clear?

  11. Zach says:

    Interesting post. I wouldn’t be so utterly depressed about this topic if it weren’t for the widespread apathy on this issue, as well as lack of leadership at a federal level. If America led the charge on fighting climate change, we’d all be laughing about this issue a decade from now, because we would be well on our way to solving it. We control our own future, so if we get to a point where we have catastrophic climate changes, we’ll have ourselves to blame.

    Also, not to downplay this, but Joe what do you think about recent studies published that say climate sensitivity (in terms of doubling of CO2) is actually less than previously thought?
    This paper claims that based on the last glacial maximum 20,000 years ago and climate models, the median climate sensitivity for a doubling of CO2 is 2.3C, as opposed to the commonly-believed 3C. Less bad is still bad, don’t get me wrong, but .7C seems pretty significant in terms of fighting and having more time to mitigate this looming disaster.

    At least we can put some hope in solar and other energy sources becoming cost-competitive very soon.

  12. Zach says:

    Direct link to the paper I was referencing:

  13. Merrelyn Emery says:

    Lewis, I understand your concern and have reluctantly come to agree with it as long as it is extremely tightly controlled, is based on research which treats the planet as a whole open system, and there are enforceable sanctions against rich, private enterprise efforts by ‘cowboys’ to put their own bright ideas into effect.

    All it will probably do is buy us some time but just at the moment, it looks like we will need that time to restore sanity, ME

  14. scas says:

    According to geoengineering theory temperature rise will spike almost immediately, possibly creating worse conditions than if SRM (or global dimming in this case) was not used.

    According to Hansen and Ramanathan, we’ve severely underestimated global dimming…

    According to Climate Code Red there will be an instantaneous 0.4 C rise..

    According to James Lovelock, contrails, shiptrails, and combustion is blocking 2-3 degree C of warming…

    In any case, i’ve seen geoengineering suggested in order to mask the deleterious effects of reducing reflective pollution.

  15. Mulga Mumblebrain says:

    I had heard that there was an immediate increase of 1 degree C in the days after September 11, 2001, when air traffic was grounded in the USA.

  16. Raul M. says:

    A naked scientist.
    A naked scientist might want some clothes and to compensate with carbon recovery for the total carbon output for the attire the scientist could offset with biochar to put carbon into savings.
    For high emissions clothing and obtaining such a service worker might need to put many lbs. of biochar into savings to keep a carbon balance for that one endeavor.
    At that point without social structure and training one might become confused and discouraged!!!

    Otherwise without doing so eventually all goes to carbon floating in the air and ourselves too. Maybe someday we will all come back down to the ground having learned something.

  17. Raoul says:

    Zach, Joe has already blogged about the study you mention (Schmittner et al.) here

  18. Rabid Doomsayer says:

    The days got warmer but the nights got colder

  19. John McCormick says:

    Lewis and ME, I’m coming around to similar ideas about greater involvement of the UN to begin a binding structure to oversee any attempt to massively apply a tourniquet to the hemorrhage we have caused.

  20. Esko Pettay says:

    Even voluntary reductions will make a big difference: Projected RCP4.5 aerosol emission reductions result in 1 C additional global warming by the end of the 21st century.

    And Prof. Solomon has stated that aerosols cool as much as removing 30-150 ppm of CO2 from the atmosphere. IPCC reports also show that aerosols might have a very strong cooling effect (with very high uncertainty, but cooling effect anyway).

    Many others have also shown that reducing aerosol emissions will cause additional warming. We do have to consider the health effects of aerosol emissions but there are areas where such emissions don’t have negative health effects (ocean going ships). So it might be a good idea to reduce only the harmful aerosol emissions now and clean the rest when we have greenhouse gas emissions under control.

  21. Zach says:

    Thanks, I missed that post for some reason.

  22. Amoeba says:

    This link is dead [404]:
    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 — “We have shown that this dramatic rise in sea level is associated with an increase in CO2 levels of about 100 ppm”.

    This is one that works.

  23. Leif says:

    Or in the ground having learned nothing…

  24. Raul M. says:

    Not taking into account the revenge of nature, what is mankind’s carbon debt to the Earth’s climate? Revenge of Nature could be considered as interest and penalties to the carbon debt.
    Bankrupt. Bankruptcy.
    Certainly no bank could sustain service operating with such a red ink ledger.

  25. ryan says:

    Air traffic effects climate:

    air traffic won’t run out of fuel before social disruptions such as massive strikes, economic downturn, or “terrorism” cause declines in air travel.

  26. Raul M. says:

    Anyway I’m thinking of a new type of service business, say a service that does boichar budget for common activities. Say 60 lbs. Of biochar put in the ground as a nature repayment account for the burning of 10 gallons of gas. Repayment for car might be 2000 lbs. of biochar. Nice dinner say 5 lbs. Plane trip cross country at 2000 lbs.
    It should be easy that a carbon repayment plan could keep several servants busy to keep up with the activities of just one successful business person.
    Any helpful thoughts?

  27. catman306 says:

    You might actually have a workable plan, instead of a carbon tax, the carbon is repaid with biocharcoal. This is a jobs program for those gathering bio-materials and manufacturing biocharcoal, a farm aid program plowing the land, burying the biochar and enriching the soil, and an atmospheric gas re-balancing program reclaiming CO2 from the atmosphere.

    I wonder how much this program would add to the price of fossil fuel? It might be a price we have to pay.

  28. Joe Romm says:

    FIxed. Thanks.

  29. Raul M. says:

    No need to wait for the world to be saved.
    Hobo stove to the rescue.
    Just pull the charcoal chunks out and dunk in water.

  30. Lou Grinzo says:

    I’m going to be slammed for this, but please hear me out, everyone.

    Capturing and sequestering carbon from the air in an affordable manner is definitely a high priority item. It’s global even if done in only one place (i.e. it leverages the fact that CO2 is a well mixed gas), and it attacks the problem at the root, the basic mechanism that’s causing the warming.

    But imagine this scenario: We invent a way to suck carbon out of the air and sequester it at a reasonable cost/ton. I think that’s a quite low probability event, but for the sake of discussion assume it happens. As soon as some country or private entity commences carbon sucking on a large scale, that will reduce the pressure on other entities to reduce their emissions. In effect, it changes the basic supply/demand relationship in the marketplace by making each additional ton of CO2 emitted slightly less damaging (since it pushes the atmospheric level to a lower level than it would in the absence of the carbon sucking), and therefore slightly less valuable to avoid emitting. I would fully expect to see some entities pull back slightly in their CO2 mitigation efforts and emit slightly more than they would have sans carbon sucking.

    I know, I know — people are just itching to respond and tell me how absurd this is, that we “can’t” do things that way, etc. Yes, it is absurd, and yes it would be quite ridiculous and damaging and wildly counterproductive. But look around at this world that so fervently worships the free market and assumes it can do no wrong — which is how we got into this mess in the first place — and convince me it wouldn’t happen.

  31. Lou Grinzo says:

    Plus, we have the ongoing effort to de-sulfurize the emissions of coal power plants, with China really getting into the act as part of their effort to improve their atrocious local air quality.

    To borrow an expression from Thomas Jefferson, sulfur aerosols are like holding a wolf by the ears. You don’t like it, but you don’t dare let go.

  32. John McCormick says:

    Lou, you make a valid point. But, it isn’t going to happen. Tech challenge too great. Cost, beyond the beyond. Time is our enemy. You cann’t build an airplane in the air.

    And your comment on removing global dimming by cleaning up the particulate and aerosol emissions from stationary sources is right on point. Nobody is willing to challenge you because they believe you are right but want pollution controls to be 99.99 percent efficient anyway; just because they are stuck on clean air and not on the .5 degree C increase being masked by those effluents.

    We are running the race of our lives with one foot wedged into a bucket. But, you are either on the clean air bus or you are under it.

  33. John McCormick says:

    Lou, your comment on removing global dimming by cleaning up the particulate and aerosol emissions from stationary sources is right on point. Nobody is willing to challenge you because they believe you are right but want pollution controls to be 99.99 percent efficient anyway; just because they are stuck on clean air and not on the .5 degree C increase being masked by those effluents.

    We are running the race of our lives with one foot wedged into a bucket. But, you are either on the clean air bus or you are under it.

  34. Mulga Mumblebrain says:

    Why not re-forest the planet?

  35. Mulga Mumblebrain says:

    Precisely Ryan. Social disruption is not far away, as immiserated populations who have been ripped off by the parasites discover that they have, in addition, been lying about climate destabilisation, and we are all stuffed. One important psychological anchor of mass society is the desire to leave things better for one’s descendants. When it becomes plain that they will, in fact, die prematurely, or survive Hell (‘The living will envy the dead’), somehow, people will be unhinged, some more that others.

  36. Lewis Cleverdon says:

    Merrylyn & John –
    thanks for your confirmation of the need for Geo-E as the complement to global emissions reductions, and particularly for confirming the need of stringent UN oversight.

    The fact that 40,000 readers of Joe’s blog are unable/unwilling to put up a coherent refutation of these needs is an indication of the argument’s soundness. I could wish it were not so, as extending the scope of mitigation doesn’t ease the scale of effort needed. But such is our position – we succeed in collective international action, or fall apart into isolationism, destabilization and conflict.

    Ryan – “people will have to adjust to disaster mode and devote their energy to survival/local resources/emergency response on their own.”

    Yours is the outlook whereby I part company with the thinking of what passes for dissent in this society. Without successful collective action at the diplomatic level, there will be neither the requisite cut of global emissions nor the essential concerted effort at Carbon Recovery and Albedo Restoration to control the pipeline-warming and feedbacks resulting from society’s past conduct.

    The republican derision of government has been widely adopted by dissenters – in ignorance of the fact that government is the sole potential means of establishing an equitable and open global society – In presuming the collapse of international governmental co-operation you are thus heading straight for isolation, for internal repression and for borders – such as US-Mexico – becoming militarized with machine-gun posts and minefields.

    As for unilateral Geo-E efforts, I guess you assume they’d be run by and on behalf of Americans over the next century. Given China’s rise to global dominance, you should consider whether you’re willing to have a foreign power controlling just which nations will get the rainfall they need to survive ?
    And whether Americans would launch WW3 to prevent that outcome ?

    Global co-operation to avoid that bitter choice is plainly where it’s at.

    As a farmer I can tell you that Climate Destabilization in the pipeline precludes any prospect of autonomous farming communities enduring without successful binding international co-operation.

    Lou –
    I’d agree that the objective of Carbon Recovery efforts is critical, and that it cannot function to cut airborne stocks if nations’ ‘offsetting’ of current outputs is not precluded by the mandate of a UN supervisory body. The best rationale I’ve seen is that CR should be applied by all nations in a legal duty to recover their past carbon emissions (well-documented since 1950). This both precludes the offsetting problem and frees the logjam in treaty negotiations over “historical responsibilities”.



  37. Raul M. says:

    It’s so sad that my grandparents and parents didn’t live to know that biochar could replace carbon in the ground. Some of them did learn the need for a reasonable response to nature for their personal choices of living. I think that if some of them had seen it in action and learned to account for their own choices they would have liked the freedom to respond.

  38. Solar Jim says:

    RE: “that will reduce the pressure on other entities”

    Lou, I’m sorry to say that I believe the important “entity” that will have partial pressure reduction are the seven seas. Attempting to remove carbonic acid gas from air, assuming zero human emissions, would likely result in outgassing from the ocean (for a long time).

  39. David Stern says:

    Capture of CO2 from the air is a big part of the story. A lot of integrated assessment models incorporate BioCCS – burning biomass and burying the carbon. These models end up with very low or negative emissions late in the century at reasonable costs but I’m skeptical that enough biomass can be harvested and burnt… The other is direct capture from the air which is an emerging area. Check out the work of David Keith (just moved to Harvard) on this. He is also CEO of a start-up company in this space.