Publication of the first contribution to IPPC’s Fifth Assessment Report

According to the close to 300 scientists of the International Panel on Climate Change’s (IPCC) Working Group I, warming of the climate system is unequivocal. This was a key message in the Working Group I contribution to the Fifth Assessment Report, “Climate Change 2013: The Physical Science Basis,” recently released by the IPCC.

The report highlights a startling increase in the Earth’s average surface temperature reflected in historical data, with the last three decades being the warmest observed since 1850. The assessment is based on multiple lines of independent evidence, and states that in addition to the warming of surface temperature, evidence shows that the oceans have warmed and snow and ice mass has diminished. The report further highlights how the global mean sea level has risen by 0.79m over the period 1901-2010, which is greater than the rate of sea level increase observed during the two previous millennia.

For the drivers of climate change the report states that CO2 concentrations have increased by 40% since pre-industrial times, along with increased concentrations of other greenhouse gasses such as methane and nitrogen. On release of the report Co-Chair of the IPCC, Thomas Stocker, further highlighted that “As a result of our past, present and expected future emissions of CO2, we are committed to climate change, and effects will persist for many centuries even if emissions of CO2 stop.”

Future climate change projections outlined in the report indicate that most of the observed climate trends will continue and worsen over the coming centuries, with temperatures increasing, heat waves becoming more likely and more frequent, yet with wet regions receiving more rainfall and dry regions receiving less. Continued warming of the oceans, retreating glaciers and ice sheets and increasing rates of global sea level rise are other important projections highlighted.

Indications what the current trends and future projections mean for systems, sectors and regions will be dealt with in the next report of the IPCC, “Climate Change 2014: Impacts, Adaptation and Vulnerability,” which is due to be released by the IPCC Working Group II in March 2014.