Saturday, June 27, 2009

Global Warming Impact on US

Global climate change impacts in the United States are spelled out with renewed authority in a report released June 16 by the federal government.

The report's key information has been well reported here and in Earth Under Fire and other books, but bears repeating in its straightforward language and up-to-date numbers.

Human activities have led to large increases in heat-trapping gases over the past century. The global warming of the past 50 years is due primarily to this human-induced increase. Global average temperature and sea level have increased, and precipitation patterns have changed.

Human “fingerprints” also have been identified in many other aspects of the climate system, including changes in ocean heat content, precipitation, atmospheric moisture, plant and animal health and location, and Arctic sea ice.

In the U.S., the amount of rain falling in the heaviest downpours has increased approximately 20 percent on average in the past century.

Many types of extreme weather events, such as heat waves and regional droughts, have become more frequent and intense during the past 40 to 50 years. The destructive energy of Atlantic hurricanes has increased... In the eastern Pacific, the strongest hurricanes have become stronger since the 1980s, even while the total number of storms has decreased.

Sea level has risen along most of the U.S. coast over the last 50 years, and will rise more in the future. Arctic sea ice is declining rapidly and this is very likely to continue. Global temperatures are projected to continue to rise over this century.

Whether by 2-3 degrees F or more than 11 degrees depends on a number of factors, including the amount of heat-trapping gas emissions humans continue to allow and how sensitive the climate is to those emissions. Lower emissions of heat-trapping gases will delay the appearance of climate change impacts and
lessen their magnitude.

Unless the rate of emissions is substantially reduced, impacts are expected to become increasingly severe for more people and places.