New IPCC Report Shows Certainty that Human Activity is Causing Climate Change

The Intergovernmental Panel on Climate Change (IPCC) has issued its long-awaited update on the state of the climate, and the certainty that human activity is causing it has grown. This is the first of a series of reports and documents the efforts over the last seven years of Working Group I (WGI). With 209 Lead Authors, 50 Review Editors, 600 Contributing Authors and hundreds more reviewers, this volume of the Fifth Assessment Report (AR5) "provides a comprehensive assessment of the physical science basis of climate change."

Among the key findings are that it is unequivocal, i.e., absolute certainty, that the the planet is warming. WGI also has increased the confidence that human activity is the major cause. In 2007 the IPCC conservatively stated that there was a greater than 90% certainty of human causes - that has now been raised to 95%-100% certainty. In other words, the planet is warming and we are the main reason why.

The IPCC also states with high confidence that the Greenland and Antarctic ice sheets have been losing mass, that glaciers have continued to shrink almost worldwide, and that Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent.

There is also high confidence that sea level has been rising faster than anytime in the last two thousand years.

The IPCC AR5 report of the physical science basis can be downloaded in full at the IPCC website. A Summary for Policymakers is also available.

This is the first of four reports to be issued. The Working Group II report on impacts, adaptation and vulnerability will be issued in March 2014. The Working Group III report on mitigation of climate change will be come out in April 2014. Finally, the Synthesis Report, which summarizes all three technical reports, will be issued in October 2014.