30 September 2013
AGU Science Policy Alert 13-42
The Intergovernmental Panel on Climate Change’s (IPCC) Fifth Assessment Working Group I Report, released Friday, 27 September 2013, states “Warming of the climate system is unequivocal… The atmosphere and ocean have warmed, the amounts of snow and ice have diminished, sea level has risen, and the concentrations of greenhouse gases have increased.” Working Group I assessed the physical science pertaining to climate change including its impact on the atmosphere and oceans, particularly changes in CO2 concentrations, air and water temperatures, sea ice quantity, sea level rise, and ocean acidification.
The report confirms that humans influence the climate system and that it is “extremely likely” that anthropogenic forces play a dominant role in observed warming. This is an increased level of certainty from the previous report, published in 2007, which stated that increasing temperatures were “very likely” due to anthropogenic carbon emissions. The authors conclude that “limiting climate change will require substantial and sustained reductions of greenhouse gas emissions… [and] Most aspects of climate change will persist for many centuries if emissions of CO2 are stopped.”
Working groups on Impacts, Adaptation, and Vulnerability and Mitigation of Climate Change will follow with reports in 2014 that the IPCC will combine into a final synthesis report.
The IPCC’s newest findings affirm AGU’s Climate Change Position Statement, which asserts that climate change is a reality and humans are the dominant driver.