Friday, December 19, 2008

Some highlights of 2008 climate change science

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Some highlights of 2008 climate change science

The amount information now generated by scientific efforts to comprehend climate change can make it difficult to feel like you’re keeping up. But as 2008 draws to a close I think it is worth looking back at some of the year’s highlights.

Toward that end I checked in this week with Don Wuebbles, who is a professor of atmospheric sciences at the University of Illinois and a lead author on the first two international assessments of climate change sponsored by the United Nations. Recognizing the continued, vociferous attempts to sow confusion by interest groups opposed to changes in public policy, Wuebbles emphasized that ongoing research substantiates the idea that the earth’s climate is changing significantly, and that that change is being driven by human activity.

The most dramatic aspect of the climate change story this year was the retreat of sea ice in the artic. Since 1979 scientists have been using satellites to measure the extent of arctic sea ice, and they use the minimum area it occupies in September as a benchmark for making comparisons among years. This year’s minimum was the second lowest recorded since satellite measurements began, following the record low set last year, and it was 34 percent lower than the average over the past three decades. [For short accounts see Sept. 17 NY Times article by Andy Revkin and Oct. 3 article from ScienceDaily. For much more information and cool animations of polar sea ice see "The Cryosphere Today" by William Chapman and others with the U of I Department of Atmospheric Sciences Polar Research Group.] At one point this summer both the Northwest Passage over Canada and the Northern Sea Route over Russia were open at the same time. The continued decline of ice in the arctic served to underscore the importance of designating polar bears as a threatened species, which U.S. Fish and Wildlife Service did this past March after years of footdragging.

Another dramatic ice story comes from Greenland, where the focus of attention is on how fast the Greenland ice sheet is melting, and how that melting will affect sea level over the next century. The most recent estimates used by the Intergovernmental Panel on Climate Change projected that the melting of Greenland ice would contribute between one and four inches to sea level rise over the next 100 years. But a study published this summer led by a University of Wisconsin geologist suggests that projection is too conservative, and that melting Greenland ice could contribute between one and two feet to sea level over 100 years. [ScienceDaily short versionNature Geoscience long version (requires access through library or subscription).] This projection is based on analysis of how the last great ice mass to cover parts of Canada and the U.S. melted under conditions similar to those expected for Greenland in the century to come.

Closer to home, professor Wuebbles collaborated with a former student as lead authors on the climate science component of the report, Climate Change and Chicago issued in September. That report projects that by the year 2100 summers in Chicago will resemble present-day summers in Atlanta, even assuming that the global economy make dramatic moves away from fossil fuels. Even hotter conditions are projected under a business-as-usual scenario, with as many as 80 summer days with temperatures above 90 degrees, as opposed to the current average of 15. Unfortunately winters are not projected to be so much warmer. The Chicago climate report also projects disruptive changes in precipitation patterns, with increased precipitation and greater storm events occurring in winter and spring, but less rainfall when it is most needed, later in the growing season.

The good news evident in Chicago’s Climate Action Plan is that it is possible for scientists, policymakers, and stakeholders to work together to confront the challenges posed by climate change. Perhaps there’s hope for such progress at the national level in the year to come.