I'm a professor at U Michigan and lead a course on climate change problem solving. These articles often come from and contribute to the course.
By: Dr. Ricky Rood , 4:26 AM GMT on October 01, 2009
Arctic Extreme Feedbacks
My previous blog was on a paper that argues from a variety of points of view that the Arctic is showing definitive warming, despite a substantive reduction in solar radiation due to the wobbling of the orbit of the Earth. This blog is also on the Arctic, and specifically a scientific assessment sponsored by the World Wildlife Federation (WWF). (Yes, I know that the WWF takes an advocacy position.) The report has excellent summaries of scientific studies as well as basic references.
This WWF report is an assessment of the state of the Arctic comprised of information since the IPCC Fourth Assessment Report. Part of the motivation for this report is that at the time of the IPCC report there was controversy within the scientific community that the melting of ice in Greenland and, perhaps, West Antarctica was occurring much faster than reported in the IPCC Fourth Assessment Report. One consequence of more rapid melting of the ice sheets would be more rapid and larger than predicted sea level rise.
There have been a number of “official” responses to evaluate the observations and predictions and to improve the predictions. The European Union has funded a program called Ice2sea, and in the U.S. SeaRISE is a community organization, which is now sponsored by NASA. Both of these efforts strive to take an integrated approach to put together observations and models to improve predictions to provide input for the next IPCC report in 2013. You might recall that the IPCC is based entirely on assessment of papers that have appeared in the peer-reviewed literature; therefore, these projects need to deliver results in about 2 years.
Back to the WWF Report: Arctic Climate Feedbacks: Global Implications. This report has six chapters written by experts in the field. The unique focus of the report is on feedbacks. That is, if the Arctic climate is warmed by greenhouse gas warming, does the Arctic climate respond to this warming in a way that increases the warming more, or does it respond in a way to reduce the warming, bring it back to “normal.”
The feedback that is easiest to understand is the feedback related to ice and snow. For example, if the ocean is covered with ice, which is “white,” then much of the summertime sunlight will be reflected back to space. If there is warming, and the ice melts, and the “white” ice is replaced by the “dark” ocean, then the ocean will absorb more heat from the Sun and there will be more warming. Warming begets more warming; this is a “positive feedback.” If you march through all of the feedbacks that might exist, the strongest and most assured feedbacks are positive. In general, the present day Earth will respond to warming with more warming.
The WWF report studies a whole variety of feedbacks. There is discussion on how and why large changes in the Arctic impact both the circulation of the atmosphere and the ocean. A large and definitive feedback is the fact that a warming Arctic will release greenhouse gases that are stored in frozen land, cold water, and at the bottom of the ocean. The store of greenhouse gases in these reservoirs is enormous. For example, “There is more carbon in methane hydrates that in all the fossil fuel deposits in the world.”
The feedback, here, is the fact that warming by greenhouse gases, releases greenhouse gases, which cause more warming. Methane is a far more effective greenhouse gas than carbon dioxide. Much of the methane is stored in ocean sediments that are in relatively shallow water. There is already observed release coming from these sediments, but we don’t yet know whether or not these releases are contributing to warming. There is a possibility, however, of huge sudden releases of methane.
The gist of the WWF report is that when we consider the full role of feedbacks from changes in the Arctic, then the possibility of rapid global consequences is quite high. While large decreases in greenhouse gas emissions will help mitigate this change, it is my opinion that we have already reached a point where we must anticipate such warming, assess risk, and plan for adaptation.
The existence of feedbacks as described in WWF report is not surprising, and there is ample evidence of these feedbacks naturally impacting the climate. For example absorption and capture of methane and carbon dioxide in the ice age cycles is well documented. This is, surely, related to the roles that the oceans, permafrost, and biological activities play in the controlling the composition of the atmosphere.
WWF Report: Arctic Climate Feedbacks: Global Implications.
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