The world’s scientists are more than 90% certain that human activity – primarily burning fossil fuels to power cars, power plants, and factories – is responsible for most of the observed increase in global average temperatures since the mid-20th century, according to a consensus report released early this morning by the Intergovernmental Panel on Climate Change (IPCC), a United Nations body charged with assessing the scientific record on global warming.
The report finds that warming of the climate is “unequivocal” and warns that temperatures could further increase substantially if serious action is not taken to reduce emissions of the pollutants that cause global warming.
Cars and power plants are the largest sources of these emissions, though the U.S. could reduce its emissions immediately using on-the-shelf technologies to improve energy efficiency and shift to renewable energy sources.
Today’s report is the first volume of the IPCC’s Fourth Assessment Report. It synthesizes the peer-reviewed research published prior to 2006 on the science underlying global warming. Additional volumes, examining global warming impacts and options for reducing future warming, are due out later this year. The full report includes input from more than 2,500 experts worldwide. The IPCC released its last assessment report in 2001.
Among the major findings of today’s report include the following:
- Human Activities to Blame: It is very likely (>90%) that human activities – primarily burning fossil fuels – have caused most of the observed increase in global average temperatures since the mid-20th century.
- Record Temperatures: 11 of the last 12 years rank among the 12 warmest years on record. Cold days, cold nights, and frost have become less frequent, while hot days, hot nights, and heat waves have become more frequent.
- More Intense Tropical Storms: There has been an increase in intense hurricane and tropical typhoon activity since about 1970. The report also finds that it “is likely that future tropical cyclones (typhoons and hurricanes) will become more intense, with larger peak wind speeds and more heavy precipitation” associated with warmer oceans.
WashPIRG analysts note the report is inherently conservative because it reflects the consensus of hundreds of parties, including industry groups and governments opposed to taking action to reduce global warming pollution. In addition, the report does not include any research published in 2006, though there have been major research developments on sea level rise and hurricane intensity, among many other areas.
