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2007 Intergovernmental Panel on Climate Change Assessment Reports
Related Links
Working Group I
- EPA/DOE/DOC Joint Press Release
- White House Press Release
- DOC Press Release
- NOAA Support for IPCC
- USGRCP WGI Resources
Working Group II
- White House Press Conference
- USGCRP WGII Resources
- NOAA Leads Climate Impact and Adaptation Activities
- U.S. Climate Change Science Program Press Release
Working Group III
Working Group I | Working Group II | Working Group III
The Intergovernmental Panel on Climate Change (IPCC) 
was established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP) to provide a comprehensive and objective assessment of the state of knowledge on climate change to the world community.
In 2007, the IPCC released reports covering climate change science (Working Group I), climate change impacts and adaptation (Working Group II) and climate change mitigation (Working Group III). They recently released an overall synthesis report (PDF) (23 pp., 6.4 MB, About PDF ) summarizing findings from the 3 main reports. The IPCC has previously assessed climate change issues in 1990, 1995 and 2001. Content on EPA's Climate Change Web site will be updated to reflect the findings and conclusions of these IPCC reports following the release of these assessments.
The United States government has been a significant contributor to these reports, with scientists serving as Lead and Contributing Authors and providing comments in the official government review process - in which EPA was involved. Official government delegations, including from the United States, have approved the Summary for Policymakers for Working Groups I and II and III and the respective underlying reports.
The Summary for Policymakers of the second volume of the IPCC's new assessment report "Climate Change 2007: The Physical Science Basis" was released on February 2, 2007. You may download the Summary for Policymakers from the IPCC Web site . The full report is now available on the Working Group I Web site .
The report, prepared by IPCC Working Group I, assesses the current scientific knowledge of the natural and human drivers of climate change, observed changes in climate, the ability of science to attribute changes to different causes, and projections for future climate change that include temperature, precipitation and sea level rise.
The key findings in the Working Group I Summary for Policymakers follow:
- Greenhouse gas concentrations have markedly increased since 1750 and far exceed pre-industrial values.
- Temperatures are increasing, sea levels are rising and ice is melting. The warming of the climate system is "unequivocal."
- Human activities have very likely1 caused most of the warming over the past 50 years.
- Improved computer modeling has increased confidence in future climate projections: temperatures will continue to increase, sea levels will continue to rise, and ice will continue to melt.
Working Group II (Impacts and Adaptation)
The Summary for Policymakers of the second volume of the IPCC's new assessment report “Climate Change 2007: Climate Change Impacts, Adaptation and Vulnerability” was released on April 6, 2007. You may download the Summary for Policymakers from the IPCC Web site . The full report is now available on the Working Group II Web site .
The report, prepared by IPCC Working Group II, assesses current scientific understanding of impacts of climate change on natural and human systems, their capacity to adapt and their vulnerability.
The key findings in the Working Group II Summary for Policymakers follow:
- Evidence from many parts of the world show that people, plants and animals are being affected by regional climate changes, particularly temperature increases.
- Warming caused by human activities has likely1 had a discernible influence on plants and animals.
- More detailed information is now available about how climate change will impact water resources, ecosystems, agriculture and forestry, health, coastlines and regions of the world. These impacts will likely be both positive and negative across regions although it is very likely1 that all regions will experience declines in benefits or increases in costs if global average temperatures warm more than 3.6-5.4 degrees F.
- A mix of adaptation (preparing for and responding to climate change impacts) and mitigation (e.g. reducing greenhouse gas emissions) can reduce the risks of climate change.
1 On this page the following terms, as defined by IPCC 2007, are used to 99% probability of occurrence, Extremely likely > 95%, Very likely > 90%, Likely > 66%, More likely than not > 50%, Very unlikely < 10%, Extremely unlikely < 5%.
Working Group III (Mitigation)
The Summary for Policymakers of the third volume of the IPCC’s new assessment report “Climate Change 2007: Mitigation for Climate Change” was released on May 4, 2007. You may download the Summary for Policymakers from the IPCC Web site . The full report is now available on the Working Group III Web site .
The report, prepared by IPCC Working Group III, assesses greenhouse gas mitigation options in each sector of the global economy, addressing the economic and environmental costs and benefits of mitigation, the technical aspects of mitigation options, and potential cross-sectoral synergies and trade-offs. It also assesses the compatibility of near-term greenhouse gas mitigation activities with long-term climate stabilization pathways.
The key findings in the Working Group III Summary for Policymakers follow:
- Global greenhouse gas emissions have grown since pre-industrial times, with an increase of 70% between 1970 and 2004. With current climate change mitigation policies and related sustainable development practices, global GHG emissions will continue to grow over the next few decades.
- There is substantial economic potential for the mitigation of global GHG emissions across all sectors over the coming decades, where economic potential assumes that additional policies have been put into place to remove barriers and include social costs and benefits.
- In order to stabilize the concentration of GHGs in the atmosphere, emissions would need to peak and decline thereafter. The lower the stabilization level, the more quickly this peak and decline would need to occur.
- The stabilization levels modeled are achieved by deployment of a portfolio of technologies that are currently available and those that are assumed to be commercialized in coming decades.
- Macroeconomic costs for multi-gas mitigation, consistent with emissions trajectories towards stabilization between 445 and 710 ppm CO2-eq, are estimated at between a 3% decrease in global GDP and a small increase in 2030 compared to the baseline, and 5.5% decrease and a 1% gain in 2050. Most estimates assume perfect implementation. Costs increase if some regions, sectors, options, or gases are excluded. Costs decrease with lower baselines and use of revenues from carbon taxes and auctioned permits. For specific countries and sectors, costs vary considerably from the global average.
