Reality has overtaken the political games that have surrounded the subject of global warming in the US for the past decade or more. In a paper published this past summer, James Hansen, the climate scientist at NASA who famously defied Bush's anti-science agenda, has asserted for the first time in a peer-reviewed publication that a tipping point most likely exists at or near 1 degree Celsius above the year 2000 average global temperature. This tipping point will almost certainly be surpassed if an atmospheric concentration of 450 parts per million by volume (ppmv) of carbon dioxide (CO2) is reached. We are currently at 384ppmv, and current rates of increase are at 2ppmv/yr and rising. Another decade or less will put us over 400ppmv, but that's not all. By then, the energy infrastructure that will already be in place will virtually guarantee that we will exceed the tipping point by 2050, unless we as a species abandon significant crucial energy infrastructure in a manner that will cripple economies all over the world. This will place the human race in the difficult position of deciding whether to starve a quarter to a third of the world's population by crippling economies worldwide to try to avoid melting the Greenland and West Antarctic Ice Sheets, or starve a quarter to a third of the world's population when they melt.
Hansen and the other forty-six authors of this paper present compelling evidence with a high level of certainty to show that if the Earth's average global temperature increases by just 1 degree Celsius, the West Antarctic Ice Sheet will melt very quickly, certainly by the end of the century. If this happens, sea levels will rise by 4-6 meters (13-20 feet), and the surface of the Earth will lose tens or hundreds of thousands of square miles of land area, much of it in heavily populated and/or economically important regions. Washington DC, New York, Los Angeles, Bangladesh, Indonesia, Tokyo, Hong Kong, Shang Hai, London, Amsterdam, Hamburg, and Haifa would be affected, to name but a few; and inland areas such as flood plains next to rivers would also be affected. They furthermore show that this melting will most likely not happen gradually, but suddenly, when enough heat is present in the summer to cause the ice to start moving on top of liquid water, lubricating its movement into the sea. They also suggest based on an earlier paper that if the Arctic Ocean is free of sea ice in the summer and fall, substantial or total melting of the Greenland Ice Sheet is virtually certain, and hypothesize this melting also may happen much more quickly than is currently believed. This will add a further 2-3 meters (6-10 feet) of sea level rise, for a total of 6-9 meters (20-30 feet).
Worst of all, this paper suggests that it is possible that the continental shelves, the relatively shallow areas just off the coastlines, will experience enough warming to trigger the decomposition of methane clathrates known to exist in those areas, which could result in an even stronger feedback and raise the temperature far more. The decomposition of these methane clathrates has been presented in prior scientific papers as a "doomsday scenario" in which the Earth's climate is permanently and irrevocably altered to be far warmer than it has been in millions of years. The paper referenced above theorizes that it was responsible for the Paleocene-Eocene Thermal Maximum, a lesser mass-extinction event in which 40% of the species in the ocean died off.
On the other hand, if we act now, we can stop the problem before we get to that first tipping point without starving anyone. We're not talking about numb nutz not being able to drive his Hummer any more; we're talking about a couple billion people or more starving to death, and if you think they'll go quietly, I suggest you consider that quite a few of them live in China and India, both of which own nuclear weapons. And even if we act now, if the Greenland Ice Sheet melts, which is likely if the secondary paper that Hansen et. al refer to is correct, we may already be looking at significant land area loss in the regions mentioned above, and more quickly than we had feared except in our worst expectations.
Many scientists have been warning about the probable existence of such tipping points for years (see here for an article in the Washington Post that scratches the surface of this subject). The problem was, we didn't have any clear idea where they might be. Now we know at least one of them. Furthermore, it is now clear that we have already passed another one: the one at which the Arctic sea ice all melts. If current CO2 levels are sufficient to cause the incredible events of the past year in the Arctic Ocean, there is no hope of slowing emissions in time to save the Arctic sea ice; the Arctic Ocean will be free of ice in the summer within the decade, and that's now virtually certain. Unless we act quickly and decisively, the Greenland Ice Sheet will be gone by the end of the century, and almost certainly much sooner than that. Chaos will ensue. We need to find out very quickly whether it is possible to reverse the changes in the Arctic.
The implications of this coldly analytical paper are terrifying; we are looking at climate conditions that have not existed in the history of the human race. Massive dislocations, political unrest, and economic chaos are certain unless we act immediately. Some measure of them may already be inevitable. Doing nothing is no longer an option, and even if we do all we can, we may already be in serious trouble.
The NASA GISS news release is available here. The paper is available here. The abstract of the paper reads as follows:
We investigate the issue of "dangerous human-made interference with climate" using simulations with GISS modelE driven by measured or estimated forcings for 1880–2003 and extended to 2100 for IPCC greenhouse gas scenarios as well as the "alternative" scenario of Hansen and Sato (2004). Identification of "dangerous" effects is partly subjective, but we find evidence that added global warming of more than 1C above the level in 2000 has effects that may be highly disruptive. The alternative scenario, with peak added forcing ~1.5 W/m 2 in 2100, keeps further global warming under 1C if climate sensitivity is ~3C or less for doubled CO2. The alternative scenario keeps mean regional seasonal warming within 2 standard deviations of 20th century variability, but other scenarios yield regional changes of 5–10 standard deviations, i.e. mean conditions outside the range of local experience.
We conclude that a CO2 level exceeding about 450 ppm is "dangerous", but reduction of non-CO2 forcings can provide modest relief on the CO2 constraint. We discuss three specific sub-global topics: Arctic climate change, tropical storm intensification, and ice sheet stability. We suggest that Arctic climate change has been driven as much by pollutants (O3, its precursor CH4, and soot) as by CO2, offering hope that dual efforts to reduce pollutants and slow CO2 growth could minimize Arctic change. Simulated recent ocean warming in the region of Atlantic hurricane formation is comparable to observations, suggesting that greenhouse gases (GHGs) may have contributed to a trend toward greater hurricane intensities. Increasing GHGs cause significant warming in our model in submarine regions of ice shelves and shallow methane hydrates, raising concern about the potential for accelerating sea level rise and future positive feedback from methane release. Growth of non-CO2 forcings has slowed in recent years, but CO2 emissions are now surging well above the alternative scenario. Prompt actions to slow CO2 emissions and decrease non-CO2 forcings are required to achieve the low forcing of the alternative scenario.
We're no longer talking about "might" or "maybe" in the core scientific community engaged in this research. We're also not talking about a single author, or even a couple. This paper has the following list of authors:
J. Hansen 1,2 , M. Sato 2 , R. Ruedy 3 , P. Kharecha 2 , A. Lacis 1,4 , R. Miller 1,5 , L. Nazarenko 2 , K. Lo 3 , G. A. Schmidt 1,4 ,
G. Russell 1 , I. Aleinov 2 , S. Bauer 2 , E. Baum 6 , B. Cairns 5 , V. Canuto 1 , M. Chandler 2 , Y. Cheng 3 , A. Cohen 6 ,
A. Del Genio 1,4 , G. Faluvegi 2 , E. Fleming 7 , A. Friend 8 , T. Hall 1,5 , C. Jackman 7 , J. Jonas 2 , M. Kelley 8 , N. Y. Kiang 1 ,
D. Koch 2,9 , G. Labow 7 , J. Lerner 2 , S. Menon 10 , T. Novakov 10 , V. Oinas 3 , Ja. Perlwitz 5 , Ju. Perlwitz 2 , D. Rind 1,4 ,
A. Romanou 1,4 , R. Schmunk 3 , D. Shindell 1,4 , P. Stone 11 , S. Sun 1,11 , D. Streets 12 , N. Tausnev 3 , D. Thresher 4 , N. Unger 2 ,
M. Yao 3 , and S. Zhang 2
1 NASA Goddard Institute for Space Studies, New York, NY, USA
2 Columbia University Earth Institute, New York, NY, USA
3 Sigma Space Partners LLC, New York, NY, USA
4 Department of Earth and Environmental Sciences, Columbia University, New York, NY, USA
5 Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY, USA
6 Clean Air Task Force, Boston, MA, USA
7 NASA Goddard Space Flight Center, Greenbelt, MD, USA
8 Laboratoire des Sciences du Climat et de l’Environnement, Orme des Merisiers, Gif-sur-Yvette Cedex, France
9 Department of Geology, Yale University, New Haven, CT, USA
10 Lawrence Berkeley National Laboratory, Berkeley, CA, USA
11 Massachusetts Institute of Technology, Cambridge, MA, USA
12 Argonne National Laboratory, Argonne, IL, USA
The multi-national and multi-disciplinary nature of the authors of this paper is immediately obvious. No more whining about scientists not making definite predictions and telling us what we need to do about it; this paper is a clear and urgent call to immediate action on this matter by the people in the best circumstances to know.
From now on, we can clearly label the "climate skeptics" as liars or those who uncritically believe liars. Gore has won the Nobel Peace Prize, for his recognition of the reality and imminence of this problem, and his efforts to educate and mobilize the people who can do the most in the shortest time to avert this catastrophe. The community of climate scientists has spoken clearly and concisely, and warned of imminent danger to us all, if anyone thought they had not already done so in the IPCC TAR and AR4. Failure to act now will doom our children, and perhaps ourselves, to a horror of Mathusian proportions. The question before us now is not, do we need to do anything, or even, what should we do, but, can we do anything quickly enough to avert this global disaster.
We all need to clearly understand that the scientific debate on this subject is at an end. We are faced with disaster that threatens our civilization, and may threaten our lives and our childrens'. Here's what each of us must do.
- Read and understand what the scientists say is going to happen, and what they say we might be able to avoid.
- Act in our homes, workplaces, and recreation to reduce our carbon usage as soon and as much as we can.
- Educate all we work and play with what is at stake and that ignoring or avoiding this problem is unacceptable.
- Act politically to elect or be leaders who will help solve this problem instead of ignoring it or making it worse.
I hope that we can act together to avoid the worst of these problems. If we don't, we and our children will pay the price.
