As I’m sure everyone’s aware at this point, the IPCC has released its Summary for Policymakers (PDF). We’ll have a piece
going up later today [here it is] explaining the basics of what the IPCC is and why you should care. Then Monday we’ll have a piece from Andrew Dessler on what the report says and how/whether it’s changed from the 2001 report.
For now, here are a few relevant quotes from the SPM, which I’ve stolen whole hog from Deltoid.
Here’s the heart of the matter:
Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely [defined as >90% probability] due to the observed increase in anthropogenic greenhouse gas concentrations.
In other words, there’s not much reasonable doubt left that human beings are driving global warming.
Here’s the deal on projected warming:
Best estimates and likely ranges for globally average surface air warming [by the end of the century] for six SRES emissions marker scenarios are given in this assessment and are shown in Table SPM-2. For example, the best estimate for the low scenario (B1) is 1.8°C (likely range is 1.1°C to 2.9°C), and the best estimate for the high scenario (A1FI) is 4.0°C (likely range is 2.4°C to 6.4°C). Although these projections are broadly consistent with the span quoted in the TAR (1.4 to 5.8°C), they are not directly comparable.
On hurricanes, it turns out the IPCC and the WMO statements aren’t that far apart after all, according to Pielke Jr.
One of the interesting stories in all this is just how off-base some of the early media reports were. We’ll see if post-release coverage is any better.