“Human influences are having an impact on some extreme weather and climate events, according to the report Explaining Extreme Events of 2012 from a Climate Perspective released September 5, 2013 by the Bulletin of the American Meteorological Society. Scientists from NOAA served as three of the four lead editors on the report. Overall, 18 different research teams from around the world contributed to the peer-reviewed report that examined the causes of 12 extreme events that occurred on five continents and in the Arctic. The report shows that the effects of natural weather and climate fluctuations played a key role in the intensity and evolution of many of the 2012 extreme events. However, in several events, the analyses revealed compelling evidence that human-caused climate change was a secondary factor contributing to the extreme event. “This report adds to a growing ability of climate science to untangle the complexities of understanding natural and human-induced factors contributing to specific extreme weather and climate events,” said Thomas R. Karl, LHD, director of NCDC [National Climatic Data Center]. “Nonetheless, determining the causes of extreme events remains challenging.”