No evidence has linked extreme weather events to climate change, until now. New research suggests devastating floods, droughts and storms were exacerbated by human-induced climate change caused by the burning of fossil fuels in our cars, factories and homes.
The new report, released by British and American climate agencies, analyzes a dozen extreme weather events which occurred worldwide in 2012.
“What they find is [with] about half of the events," said Thomas Karl, director of the NOAA National Climatic Data Center, "the analyses reveal compelling evidence that human-caused change was a factor contributing to the extreme event.”
The National Oceanic and Atmospheric Administration (NOAA) and Britain’s Met Office Hadley Centre edited the report. Co-editor and NOAA scientist Thomas Peterson says natural weather patterns and human induced climate change are factors in the intensity and evolution of events.
While last year’s spring and summer heat waves in the United States are attributed to normal atmospheric dynamics, climate scientists found that is not the entire story.
“They estimated that human caused climate change contributed about one-third of the magnitude of that warmth," Peterson said. "Or in terms of risk, greenhouse warming had already made very large seasonal departures from normal, like the temperatures in the spring in the Eastern U.S. about 12 times more likely to occur.”
The report also blamed human-caused climate change for the warmer ocean and atmosphere that drove the loss of sea ice in the Arctic.
That was not the case with Hurricane Sandy, the devastating storm that hit New Jersey and New York last October. Karl says the rare event might have occurred anyway.
“What the analysis was saying with the added increase of sea level, that just makes that kind of event incrementally worse," Karl said. "And in some of these events that is the kind of result that we are seeing. However, in a number of these other events we could not detect a human influence.”
High rainfall in Britain, the United States, China and Japan were mainly due to natural variability, while the report detected a warming-climate connection in precipitation in Australia and New Zealand.
“We are making great strides in our ability to understand these events," Karl said. "We attribute this to increased computational resource [and] improved quality of data sets. With these tools we continue to gain more insights into the many factors that affect the frequency and intensity as well as the spatial and temporal patterns of the extreme events.”
And, Karl adds, the more accurate information collected by climate scientists can help policy makers and the public better understand and manage the impact of climate change.