For an explanation of the terminology used by the IPCC for expressing confidence levels and likelihoods, see the table on Likelihood and confidence language at the end of this press release.

The Intergovernmental Panel on Climate Change (IPCC) today released the “Summary for Policymakers” [PDF] (SPM) of its latest assessment of climate change impacts, adaptation and vulnerability. According to the report, “[o]bservational evidence from all continents and most oceans shows that many natural systems are being affected by regional climate changes, particularly temperature increases.” Citing the accumulation of “much more evidence” over the last five years, the IPCC concludes with “high confidence” that since 1970 warming caused by humans is linked to the impacts.  The report adds that effects on people and their activities – for instance human health and agriculture -- are emerging as well. 

The SPM was drafted by the authors and Bureau members of IPCC Working Group II, and was finalized by delegates in plenary (Brussels, Belgium - 2-6 April 2007).  It summarizes the consensus view of what governments agreed was most noteworthy in the underlying report, Climate Change 2007: Impacts, Adaptation, and Vulnerability.   The SPM  is available online and will be published in hardcopy by summer 2007.  The United States and other participating governments approved the summary line-by-line and accepted the detailed assessment upon which it is based.

“This is a valuable report that our nation has contributed to in important ways through its investments in observations and research since the Third Assessment Report in 2001,” says William Brennan, Acting Director of the U.S. Climate Change Science Program.  The program, consisting of 13 departments and agencies and with an annual budget of $1.7 billion, coordinates the U.S. government’s global change research efforts.  The CCSP has supported a significant portion of the observations, individual studies and international collaborations that underpin the IPCC report.

For example, CCSP, through its Interagency Working Group on Observations, has strongly supported the analysis of space-based global land vegetation observations started in 1981, including data from both research and operational satellites.  The data have been used to study global land photosynthesis and have documented longer growing seasons and earlier onsets of spring at higher northern latitudes.   Citing the satellite observations and related analyses, the SPM says that “there is high confidence that there has been a trend in many regions towards earlier ‘greening’ of vegetation in the spring linked to longer thermal growing seasons due to recent warming.”

Dr. Brennan supports the IPCC working group’s conclusion that scientific research will remain an essential element of any strategy to cope with the impacts of climate change. “There are pressing unanswered questions about the costs of climate change impacts and adaptation, about abrupt climate change, about regional impacts, and other issues,” Brennan says. “Our ongoing research will help answer some of these questions; and we intend to use this report to inform our plans for future research.”  

A centerpiece of CCSP work is a series of 21 “synthesis and assessment” reports that will be completed in 2008 and that will integrate research results focused on important science issues and questions frequently raised by decision makers.  The series includes, for example, a report on Weather and Climate Extremes in a Changing Climate, focusing on North America.  The report will extend our understanding of  the North American implications of the IPCC’s conclusion that “some weather events and extremes will become more frequent, more widespread and/or more intense during the 21st century.”

The Working Group II SPM provides a selection of key findings regarding projected impacts for a range of climate changes projected by the IPCC for this century.  The report notes that the “[m]agnitudes of impact can now be estimated more systematically for a range of possible increases in global average temperature.”  The box below highlights some of the major projected impacts for North America. 

The IPCC report summary says that although adaptation to climate change is already occurring “on a limited basis,” additional adaptation measures will be required to cope with the impacts as climate continues to change.  However, the IPCC warns that “there are barriers, limits and costs” associated with steps that can be taken to adapt – and that “adaptation alone is not expected to cope with all the projected effects of climate change, and especially not over the long run as most impacts increase in magnitude.” 

Citing evidence that mitigation (reducing net-emissions of greenhouse gases to the atmosphere) can reduce or delay many impacts over the long-term, the IPCC notes the “value of a portfolio or mix of strategies that includes mitigation, adaptation, technological development (to enhance both adaptation and mitigation) and  research (on climate science, impacts, adaptation and mitigation).” More details on mitigation technologies, approaches, and costs will be contained in the IPCC Working Group III report scheduled for release in early May, as well as in a two-part CCSP report on Scenarios of Greenhouse Gas Emissions and Atmospheric Concentrations that will be published this Spring.

Beyond its funding of a considerable portion of the research upon which the IPCC assessment is based, the U.S. government has contributed to the assessment in other ways.  Several of the Coordinating Lead Authors are employees of Federal agencies or federally-funded research centers.  The United States contributed funding to the effort; and managed a U.S. expert and government review of the draft report, in an open process in which the public was invited to comment. 

In addition to approving the Summary for Policymakers, delegates at the IPCC meeting accepted a technical summary of the Working Group II assessment report as well as a detailed and comprehensive set of chapters that assess observed changes, future impacts and adaptation, and responses to impacts.  According to the IPCC, the full Working Group II report will be available soon on the IPCC Web site.  Hardcopy volumes of the entire Working Group II contribution (including the SPM, Technical Summary and detailed chapters) will be published by Cambridge University Press and may be available in September 2007.

The IPCC was established in 1988 by the World Meteorological Organization and the United Nations Environment Programme.  The IPCC is governed by a Plenary consisting of government representatives.  The first three assessments were published in 1990, 1995 and 2001.  The work of all three working groups has been guided by a complex, open and peer-reviewed process.  The Working Group II report alone engaged several hundred authors and nearly 50 review editors from 47 countries; and well over 800 expert reviewers.

Likelihood and confidence language

In the Summary for Policymakers, the following terms were used to indicate:

Assessed likelihood of an outcome or a result:

• Virtually certain > 99% probability of occurrence
• Extremely likely > 95%
• Very likely > 90%
• Likely > 66%
• More likely than not > 50%
• Very unlikely < 10%
• Extremely unlikely < 5%.

Confidence in a statement:

• Very high confidence At least a 9 out of 10 chance of being correct
• High confidence About an 8 out of 10 chance
• Medium confidence About a 5 out of 10 chance
• Low confidence About a 2 out of 10 chance
• Very low confidence Less than a 1 out of 10 chance.

Resources

Intergovernmental Panel on Climate Change (IPCC)

• Climate Change 2007: Impacts, Adaptation, and Vulnerability.  Summary for Policymakers [PDF].  Contribution of Working Group II to the Fourth Assessment Report of the IPCC (Geneva, Switzerland: IPCC, 2007).
• About IPCC.  The site includes links to basic information about the history, composition and procedures of the IPCC.
• Fact sheet: the Intergovernmental Panel on Climate Change and its assessment reports
• Factsheet - How the report's Summary is approved during the Plenary
• Brochure: The IPCC & the "Climate Change 2007" report (low resolution).  See also high resolution version (3,3 MB)

U.S. Government Information:

• U.S. Climate Change Science Program. Includes information related to a series of 21 “synthesis and assessment” reports.
• Links to materials from U.S. agencies posted in conjunction with the release of the IPCC Working Group II Summary for Policymakers
• Available upon request: U.S. Government comments on the “Expert and Government Review Draft of the Intergovernmental Panel on Climate Change (IPCC) Working Group II Fourth Assessment Report.”  To obtain a copy, please submit a request to ddokken@usgcrp.gov.