IPCC Fourth Assessment Report, Summary for Policymakers

IPCC AR4 Summary for Policymakers

Released on November 17, 2007, the Summary for Policymakers of the IPCC Fourth Assessment Synthesis Report represents the IPCC’s most comprehensive and definitive statement to date on climate change. The report presents the key findings of the three Working Group reports released earlier this year by the Nobel Peace Prize winning-IPCC.

The following are some of the key highlights addressed in the Synthesis Report:

  • There is strong certainty that most of the observed warming of the past half-century is due to human influences, and a clear relationship between the growth in manmade greenhouse gas emissions and the observed impacts of climate change.
  • The climate system is more vulnerable to abrupt or irreversible changes than previously thought.
  • Avoiding the most serious impacts of climate change ­-- including irreversible changes – will require significant reductions in greenhouse gas emissions. 
  • Mitigation efforts must also be combined with adaptation measures to minimize the risks of climate change. 


The Synthesis Report is the fourth and final installment of the Fourth Assessment Report. The previous three installments published earlier this year examined the physical science basis for climate change, the impacts of global climate change, and the solutions to global climate change, particularly options for reducing greenhouse gas emissions.

For the full report, visit the IPCC website. For a summary of the synthesis report, click here (pdf). Relevant materials can be linked to from the "Related Content" box above.

Statement by Eileen Claussen, President, Pew Center on Global Climate Change

November 19, 2007

The latest IPCC report underscores the need for immediate and sustained action to reduce greenhouse gas emissions, both in the United States and globally. In the United States, many states are demonstrating strong leadership, and I am confident Congress is on the path to enacting a comprehensive mandatory policy in the near future.

Globally, 2008 marks a significant milestone as the Kyoto commitments take effect. But many already have their sights set on a post-Kyoto framework, and steps toward a new international agreement will be the key issue before negotiators next month in Bali.

The ideal outcome from Bali would be a clear mandate to negotiate a comprehensive post-2012 agreement establishing fair, effective, and binding commitments for all major economies.  Unfortunately, despite the latest wakeup call from the IPCC, it appears that the United States and some other key governments are not yet prepared to negotiate real commitments.  Even if a clear negotiating mandate isn’t possible, it is imperative that any process launched in Bali leave the door open to negotiating commitments.  That way, when a new U.S. administration takes office, governments can quickly get down to the business of forging an effective and durable post-2012 framework.

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