IPCC Working Group I: The Physical Basis of Climate Change
"The Working Group I contribution to the IPCC Fourth Assessment Report describes progress in understanding of the human and natural drivers of climate change1, observed climate change, climate processes and attribution, and estimates of projected future climate change. It builds upon past IPCC assessments and incorporates new findings from the past six years of research. Scientific progress since the TAR is based upon large amounts of new and more comprehensive data, more sophisticated analyses of data, improvements in understanding of processes and their simulation in models, and more extensive exploration of uncertainty ranges." (from WGI AR4 Summary For Policymakers)
The approved Summary for Policymakers (text, tables and figures) was released at a press conference in Paris on February 2, 2007. The full Working Group I is now available online.
Among the major findings reported in the Summary for Policymakers were the following:
* Global atmospheric concentrations of carbon dioxide, methane, and nitrous oxide are currently 35%, 147%, and 18% higher, respectively, than pre-Industrial (1750) levels. Present-day concentrations of carbon dioxide and methane far exceed the natural range of these gases in the last 650,000 years.
* Global average annual temperature increased 1.3F (0.74C) between 1906 and 2005. Eleven of the last 12 years (1995-2005) rank among the 12 warmest years for average global temperature since 1850.
* It is very likely (greater than 90% chance) that most of the warming since the mid-20th century is due to human-caused increases in greenhouse gas concentrations.
* Global temperatures are projected to increase 3.2F to 7.2F (1.8C to 4.0C) by the decade of the 2090s relative to average temperature for 1980-1999. This is the best estimate range.
* Global sea level rise is projected to increase 7-23 inches (0.18-0.59 meters) relative to average sea level for 1980-1999.
(Courtesy of the Climate Impacts Group)
Link to official IPCC website: http://www.ipcc.ch/
IPCC AR4 Report: Working Group I: Physical Basis of Climate Change
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