The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by the World Meteorological Organization and the United Nations Environmental Program to evaluate the risk of anthropogenic climate change. The evaluation is based primarily on peer-reviewed publications. The IPCC has produced reports on their findings in 1990, 1995, 2001, and 2007 (as well as a supplemental report in 1992). Climate Change 2007 is the Fourth Assessment Report (AR4). The Fourth report will be issued in four parts:
1. Working Group I Report: The Physical Science Basis
2. Working Group II Report: Impacts, Adaptation, and Vulnerability
3. Working Group III Report: Mitigation of Climate Change
4. The Synthesis Report
The IPCC will release both a full report and a summary for each of the four parts. To date, only the Summary for Policymakers of Working Groups I and II findings has been released. The Working Group I report was produced by about 600 scientists and government representatives from 40 countries, including the United States. More than 620 experts and government representatives reviewed the report. Before issuing the report, line-by-line review and agreement was carried out by representatives from 113 countries.
Some of the more important conclusions and observations from the report include:
• Warming of the climate is unequivocal
• Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely (more than 90% confidence) due to observed increases in anthropogenic greenhouse gases
• Carbon dioxide, methane, and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values
• The amount of carbon dioxide in the atmosphere in 2005 (379 ppm) by far exceeds the natural range of the last 650,000 years (180 to 300 ppm)
• The amount of methane in the atmosphere in 2005 (1774 ppm) by far exceeds the natural range of the last 650,000 years (320 to 790 ppm)
• The primary source of increase in carbon dioxide is fossil fuel use, but land use changes also make a contribution
• The primary source of increase in methane is very likely to be a combination of human agricultural activities and fossil fuel use
• Eleven of the last 12 years in this period (1995-2006) rank among the top 12 warmest years in the instrumented record (since 1850)
• Warming in the last 100 years has caused about a 0.74 °C (1.33 °F) increase in the global average temperature
• Oceans have been absorbing more than80% of the heat added to the climate system, and ocean temperatures have increased to depths of at least 3000 m (9800 ft)
• It is likely that greenhouse gases would have caused more warming than observed if not for the cooling effects of volcanic and human-caused aerosols
• Average North American temperatures during the last 50-year period were very likely (>90% confidence) higher than during any other period in the last 500 years and likely (>66% confidence) the highest in at least the last 1300 years
• Mountain glaciers and snow cover have declined on average in both hemispheres."
• Losses from the land-based ice sheets of Greenland and Antarctica have very likely (>90%) contributed to sea level rise between 1993 and 2003.
• Ocean warming causes seawater to expand, which contributes to sea level rising.
• Sea level rose at an average rate of about 1.8 mm/year during the years 1961-2003. The rise in sea level during 1993-2003 was at an average rate of 3.1mm/year. It is not clear whether this is a long-term trend or just variability.
• Antarctic sea ice shows no significant overall trend, consistent with a lack of warming in that region.
• There has been an increase in hurricane intensity in the North Atlantic since the 1970s, and that increase correlates with increases in sea surface temperature.
• The observed increase in hurricane intensity is larger than climate models predict for the sea surface temperature changes we have experienced.
• There is no clear trend in the number of hurricanes.
• It is more likely than not (>50%) that there has been some human contribution to the increases in hurricane intensity.
• It is likely (>66%) that we will see increases in hurricane intensity during the 21st century.
Summary for Policy Makers PDF

http://zfacts.com/p/814.html | 01/18/12 07:18 GMT
Modified: Thu, 17 May 2007 13:13:41 GMT