I can't help but start with a few corrections to other blogs on this issue. ABC's rather half-baked analysis of the Hansen paper described it as a NASA-Columbia University paper. While it's true that these are the principle institutions, the paper is authored by 46 climatologists from 12 different institutions, private as well as public.
Dangerous human-made interference with climate: a GISS modelE study
J. Hansen1,2, M. Sato2, R. Ruedy3, P. Kharecha2, A. Lacis1,4, R.Miller1,5, L. Nazarenko2, K. Lo3, G. A. Schmidt1,4, G. Russell1, I. Aleinov2, S. Bauer2, E. Baum6, B. Cairns5, V. Canuto1, M. Chandler2, Y. Cheng3, A. Cohen6, A. Del Genio1,4, G. Faluvegi2, E. Fleming7, A. Friend8, T. Hall1,5, C. Jackman7, J. Jonas2, M. Kelley8, N. Y. Kiang1,
D. Koch2,9, G. Labow7, J. Lerner2, S. Menon10, T. Novakov10, V. Oinas3, Ja. Perlwitz5, Ju. Perlwitz2, D. Rind1,4, A. Romanou1,4, R. Schmunk3, D. Shindell1,4, P. Stone11, S. Sun1,11, D. Streets12, N. Tausnev3, D. Thresher4, N. Unger2, M. Yao3, and S. Zhang2
1NASA Goddard Institute for Space Studies, New York, NY, USA
2Columbia University Earth Institute, New York, NY, USA
3Sigma Space Partners LLC, New York, NY, USA
4Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
5Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
6Clean Air Task Force, Boston, MA, USA
7NASA Goddard Space Flight Center, Greenbelt, MD, USA
8Laboratoire des Sciences du Climat et de l’Environnement, Orme des Merisiers, Gif-sur-Yvette Cedex, France
9Department of Geology, Yale University, New Haven, CT, USA
10Lawrence Berkeley National Laboratory, Berkeley, CA, USA
11Massachusetts Institute of Technology, Cambridge, MA, USA
12Argonne National Laboratory, Argonne, IL, USA
Needless to say this is a study of rather significant impact. References are available in the original paper for those who wish to dig further.
In this paper, Hansen and colleagues use a global climate model that they developed over a number of years to predict temperature changes. It isn't perfect but it's PDG (pretty damn good). This model generally predicts a temperature increase of 3°C for a doubling of CO2 and is consistent with ancient (paleo) records of climate change (the best predictors we have of future climate behavior). As with other models, it projects that the largest temperature increases will occur in the polar regions. This is important because, as Hanson argues, the most likely catastrophic change will be sea level rise due to melting of ice sheets and glaciers.
Hansen emphasizes that the melting of the polar ice caps is a non-linear function and that the stage is currently set for dramatic acceleration of this process. Supporting observations include (among others) thinning of ice sheets, acceleration of glaciers and dramatic increases in the melting of ice at both poles over the last 3-5 years. That's particularly concerning since these ice masses were not melting appreciably just a decade ago. He also notes that ancient (paleo) climate records show a time in the past where CO2 was between 350 and 450 ppm (the current level is 384 ppm), the poles were ice-free, global temperatures were 2-3°C higher and the sea levels were approximately 25 meters (81 feet) higher than at present. Conclusion: it won't take much to push us past this tipping point, and we may have already gone too far.
He points out that there are positive climate feedbacks that are not accounted for in the climate models. These include increased release of methane from melting permafrost (already observed), saturation of the oceans with CO2 ( already observed for the Southern Ocean) and decreased capacity for CO2 in warmer oceans. Hansen also points out that unrestrained increases in CO2 could result in major releases of greehouse gases from methane hydrates resulting in runaway temperature inflation.
Another important prediction of the model is that if global CO2 exceeds 450 ppm, the temperature increases start to become self-sustaining, i.e. perpetual for at least the next few millenia. Hansen's major concern is that the models used by the IPCC in its recent projections are conservative. Independent of Hansen's concerns, observations that these models are underestimating the climate impact of greenhouse gas emissions are becoming more frequent, especially in the modeling of ice melting at the poles. Add in the recent, ominous uptick in the annual rate of global CO2 increase and the ( saturation of the Southern Ocean) and the picture looks grim.
Hansen remains optimistic that we can make the necessary changes in time, but I'm not so certain. He does not take into account the almost certain foot-dragging, intransigence and generally lack of cooperation from the conservative sector in the US. If you take Bush's latest statement of non-cooperation and add in recent statements of non-cooperation from China and India, and we have a significant problem on our hands. China is a particularly important issue since it currently generates as much CO2 as the US, but unlike the US is increasing its production of CO2 at a dramatic rate. China has an aggressive internal program to reduce carbon emissions, but it has not been as effective as it needs to be. What's noteworthy is that this plan went into effect in 2001 and it is only now beginning to have a (small) effect. The message is that these types of changes take time. Starting now will begin to have an impact 5 - 10 years down the line, and the longer we wait, the more it will cost. We've gone past concern to crisis.
Is there a positive side? I don't see very much of it. A group of CEO's from large US Corporations have asked President Bush to take action. That's like asking a petulant 2 year old to share his cookies. It's not going to happen, and they know it. Note that they are not taking action themselves. From their perspective it seems to be a future problem worth some PR noise. Thanks guys.
My view is that with the catastrophic failure of government under the Bush administration, the only effective action will be grassroots organization and (possible) state support. I'm not sure that we can organize rapidly enough as a nation to have an impact without some Federal support, but that shouldn't stop us from trying.
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