Saturday, January 19, 2013

Climate Change to Profoundly Affect U.S. Midwest in Coming Decades

http://www.sciencedaily.com/releases/2013/01/130118104121.htm

Jan. 18, 2013 — In the coming decades, climate change will lead to more frequent and more intense Midwest heat waves while degrading air and water quality and threatening public health. Intense rainstorms and floods will become more common, and existing risks to the Great Lakes will be exacerbated.

Those are some of the conclusions contained in the Midwest chapter of a draft report released last week by the federal government that assesses the key impacts of climate change on every region in the country and analyzes its likely effects on human health, water, energy, transportation, agriculture, forests, ecosystems and biodiversity.

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In the Midwest, extreme rainfall events and floods have become more common over the last century, and those trends are expected to continue, causing erosion, declining water quality and negative impacts on transportation, agriculture, human health and infrastructure, according to the report.

Climate change will likely worsen a host of existing problems in the Great Lakes, including changes in the range and distribution of important commercial and recreational fish species, increases in invasive species, declining beach health, and more frequent harmful algae blooms. However, declines in ice cover on the Great Lakes may lengthen the commercial shipping season.

In agriculture, longer growing seasons and rising carbon dioxide levels are likely to increase the yields of some Midwest crops over the next few decades, according to the report, though those gains will be increasingly offset by the more frequent occurrence of heat waves, droughts and floods. In the long term, combined stresses associated with climate change are expected to decrease agricultural productivity in the Midwest.

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The rate of warming in the Midwest has accelerated over the past few decades, according to the report. Between 1900 and 2010, the average Midwest air temperature increased by more than 1 degree Fahrenheit. However, between 1950 and 2010, the average temperature increased twice as quickly, and between 1980 and 2010 it increased three times as quickly.

The warming has been more rapid at night and during the winter. The trends are consistent with the projected effects of increased concentrations of heat-trapping greenhouse gases, such as carbon dioxide released by the burning of fossil fuels.

Projections for regionally averaged temperature increases by the middle of the century, relative to 1979-2000, are approximately 3.8 degrees Fahrenheit for a scenario with substantial emissions reductions and 4.9 degrees for the current high-emissions scenario. Projections for the end of the century in the Midwest are about 5.6 degrees for the low-emissions scenario and 8.5 degrees for the high-emissions scenario, according to the report.

The draft National Climate Assessment report is available at http://ncadac.globalchange.gov. A summary of associated technical input papers is available at www.glisa.umich.edu

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