Updates on Climate Research
By BOB RYAN
Updated 5:45 PM EST, Fri, Mar 20, 2009
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Two recent research reports are projecting significant changes in the Arctic and the northeast coasts in the next 100 years due to a changing climate.
Research recently published in the journal Nature Geoscience by researchers at UCLA indicates that under a "medium" greenhouse gas emission (primarily CO2 and Methane) scenario in the coming 50-100 years, the Arctic Ocean will probably be ice free by the end of this century.
Many recent measurements have shown that the extent of Arctic sea ice in the summer is decreasing even faster than most current climate models show. The research reported by the UCLA group involved studying the projections of sea ice extent from 18 different state-of-the-art climate models and looking at trends. The results indicate that the decrease in summer Arctic sea ice coverage will continue and perhaps accelerate in a warmer climate, and probably before September 2100, the Arctic Ocean essentially will be ice-free in late summers.
According to another recent paper in Nature Geoscience, researchers using sophisticated coupled-ocean-atmosphere-general circulation models (COAGCM) found that "Human-induced climate change could cause global sea-level rise" due in part to changes in the large scale ocean circulations in the Atlantic. The study found that with the large scale circulation slowing more -- as has been happening -- in a warmer climate, the rise just from thermal expansion of the ocean would result in an average sea level rise of about 18 inches in Boston and New York and a bit more than 12 inches in Washington, along the tidal Potomac. Melting of Greenland glaciers would add to this sea level rise. The study found that sea level rises along the west coast would not be as large as along the east coast.
It is important to remember that these results are based on computer simulations of the ocean-atmosphere system and these models are getting more and more realistic, giving scientists results in greater and greater detail and also involving uncertainties not spelled out in the current study.
Finally, a note on the results from an MIT study in Part 5 of my Global Warming/Change series: The MIT Joint Program on Science and Policy of Global Change shows a 50 percent probability of a global temperature rise of about 10 degree with "no policy change" by 2100, which was quite a bit higher than their previous study and quite a bit higher than most other studies and projections. Since this is so much higher than other estimates, I looked at the global climate model used as part of the study and found that the very important climate element of cloud was according to the MIT group atmospheric dynamics component
“The atmospheric model's climate sensitivity can be changed by varying the cloud feedback.”
Clouds and aerosols/haze/pollution are still a bit of a “wild card” in the model simulations. How and which (high, middle, low) clouds will change and increase or decrease in a warming climate is an area of research by many scientists. Varying the cloud feedback of atmospheric models will certainly change model projection results so it would be very helpful for further discussion from the MIT group of how much they feel their results and projections are due to increasing CO2, and how much due to varying the cloud feedback.
First Published: Mar 19, 2009 3:21 PM EST
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