A collection of 19 peer-reviewed studies compiled in a new report released Thursday by the American Meteorological Society indicates that many of the extreme weather and climate events of 2012 are linked to human influences.
According to the report Explaining Extreme Events of 2012 from a Climate Perspective, natural weather and climate fluctuation played a key role in the intensity of many of the most extreme weather and climate events in 2012, but a secondary factor was indeed anthropogenic.
"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 Karl, the director of NOAA's National Climactic Data Center. "Nonetheless, determining the causes of extreme events remains challenging."
Three of the report's four editors were scientists from NOAA, including Thomas Peterson, the principal scientist at NOAA's National Climatic Data Center.
"The changes in climate that humans are causing are a continuing factor: We are going to see the planet continuing to warm as we go forward," Peterson said in a question and answer session at Climate.gov. "If you can understand that human influence helped to cause an event, or make it more severe, then you can recognize that such events are likely going to become more frequent in the future."
The report was compiled by an international group of 18 research teams who examined the causes of 12 extreme events that occurred on five continents and in the Arctic. Several of the events -- including warming US temperatures, record-low levels of Arctic sea ice and heavy rains in Europe and Australia -- were studied from different angles across multiple analyses and the strengths and weaknesses of the research methods were scrutinized. Yet despite the varying methods of analysis, there was significant agreement between the assessment of the same events.
In addition to the aforementioned, the climate events analyzed include Hurricane Sandy, extreme flooding in North China, heavy rainfall in Japan, rainfall deficits in Somalia and Kenya, winter drought on the Iberian Peninsula, and the extreme weather of 2012 European summer.
According to the abstract of the study, "approximately half the analyses found some evidence that anthropogenically caused climate change was a contributing factor to the extreme event examined," although the natural fluctuation of weather and climate were considered a key factor as well.