Yesterday, the Intergovernmental Panel on Climate Change (IPCC) released the Summary for Policymakers (PDF) for the Synthesis Report of the Fourth Assessment Review. That’s what the impenetrable ‘IPCC 4AR SPM’ signifies.
To clarify what that really means, it must be understood that there are a number of levels to the work of the IPCC. Every few years, there is an assessment review meant to evaluate the state of published scientific literature on climate change. The first was in 1990. Subsequent reports have been released in 1995, 2001, and 2007. Each report consists of contributions from three working groups. Each working group writes a report, and each of those reports includes a Summary for Policymakers (SPM). The three working group reports are also combined into a synthesis report, which gets an SPM of its own. That’s what came out yesterday for the Fourth Assessment Review. Each of these reports is negotiated by scientists and approved by the IPCC member states. The SPMs are hashed out by government representatives line by line. That’s what the meeting that just ended in Valencia was about.
The Fourth Assessment Review has examined far more studies than the Third Assessment Review did: 577 compared to 95. Partly on account of that, it marks a big step forward in scientific certainty about the issue. As piles of media coverage stresses, the news isn’t good.