“Our assessment of the science finds that the atmosphere and ocean have warmed, the amount of snow and ice has diminished, the global mean sea level has risen and the concentrations of greenhouse gases have increased,” said Qin Dahe, co-chair of the working group that wrote the report.
The full 2,000-page report isn’t going to be released until Monday, but the summary for policymakers with the key findings was published Friday. It contained few surprises as many of the findings had been leaked in advance.
As expected, the IPCC raised its projections of the rise in sea levels to 10-32 inches (26-82 centimeters) by the end of the century. The previous report predicted a rise of 7-23 inches (18-59 centimeters).
But it also changed its estimate of how sensitive the climate is to an increase in CO2 concentrations, lowering the lower end of a range given in the previous report. In 2007, the IPCC said that a doubling of CO2 concentrations would likely result in 2-4.5 C (3.6-8.1 F) degrees of warming. This time it restored the lower end of that range to what it was in previous reports, 1.5 C (2.7 F).
The IPCC assessments are important because they form the scientific basis of U.N. negotiations on a new climate deal. Governments are supposed to finish that agreement in 2015, but it’s unclear whether they will commit to the emissions cuts that scientists say will be necessary to keep the temperature below a limit at which the worst effects of climate change can be avoided.
Using four scenarios with different emissions controls, the report projected that global average temperatures would rise by 0.3 to 4.8 degrees C by the end of the century. That’s 0.5-8.6 F.
Only the lowest scenario, which was based on major cuts in CO2 emissions and is considered unlikely, came in below the 2-degree C (3.6 F) limit that countries have set as their target in the climate talks to avoid the worst impacts of warming.