As expected, the IPCC raised its projections of the rise in sea levels to between 26cm and 82cm by the end of the century. The previous report predicted a rise of 18cm to 59cm.
However, it did acknowledge that the climate may be less sensitive to carbon dioxide emissions than was stated in 2007. Back then, the IPCC said that a doubling of carbon dixoide concentrations in the atmosphere would likely result in 2C° to 4.5C° degrees of warming. This time it restored the lower end of that range to what it was in previous reports, 1.5C°.
The IPCC assessments are important because they form the scientific basis of UN negotiations on a new climate deal. Governments are supposed to finish that agreement in 2015, but it is 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 0.3C° to 4.8C° this century.
Only the lowest scenario, which was based on major cuts in carbon emissions and is considered unlikely, came in below limit that countries have set as their target in the climate talks to avoid the worst impacts of warming. That limit is a warming of 2C° compared with before the industrial revolution in the 18th century.
At this point, emissions keep rising mainly due to rapid growth in China and other emerging economies. However, those nations say rich countries should take the lead on emissions cuts because they have pumped carbon into the atmosphere for longer.
Climate activists said the report should spur governments to action.
“There are few surprises in this report, but the increase in the confidence around many observations just validates what we are seeing happening around us,” World Wildlife Fund’s Samantha Smith said.
The report adopted Friday deals with the physical science of climate change. Next year, the IPCC will adopt reports on the impacts of global warming, strategies to fight it and a synthesis of all three reports.