The Intergovernmental Panel on Climate Change (IPCC), the pre-eminent group of climate change scientists, has started to release its 4th Assessment Report. This report, which took almost three years, is supposed to be the hardest hitting report on the effects of climate change. Its assessment:
Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea levels.
And unambiguously, humans are the cause.
Key findings:
- Concentrations of greenhouse gases have ‘increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values’;
- Understanding of the human impact on climate has greatly improved since the last IPCC report leading to ‘very high confidence’ (at least 90%) that the human activities since 1750 has caused the rise in greenhouse gas emissions
- These greenhouse gases are the most significant cause for global warming;
- This is based on a wealth of data, both from climate modeling and actual observation (current and historical);
- For the next two decades scientists expect a warming of about 0.2°C per decade up to approximately 4°C.
- Warming is likely to increase faster in this century than in the last century. Warming will increase even if greenhouse gas emissions are stabilized.
The IPCC produces conservative estimates. Actual effects are likely to be higher.
Download the executive summary for policymakers here.
And for fans of the hockey stick, you’ll see plenty on page 15.
If you’re interested in the current politics of the IPCC the conservative think tank, the American Enterprise Institute (AEI), and ExxonMobil are giving $10,000US to scientists and economists who can poke holes in the report. This is not how science works.