Generic image,mother applying suncreen to child (Photo courtesy of AP Graphics)
Brace yourself for more hot summers ahead. Extreme weather researchers report on Thursday that climate change makes the searing summer that the struck the United States last year much more likely.
In fact, July 2012-like heat is now four times as likely to strike the Midwest and Northeast as it was in pre-industrial America when less carbon dioxide warmed the atmosphere, according to a Stanford University study. Last year's heat wave, which peaked in July - the warmest month on record for the contiguous USA - exacerbated the nation's drought, ruined crops and contributed to more than 100 deaths.
"It was a very rare event. It's now less rare given current greenhouse gas emissions," says lead author Noah Diffenbaugh, a climate scientist at Stanford's Woods Institute for the Environment.
His research is part of a trove of 19 new peer-reviewed studies by scientists worldwide that look at the possible link between climate change and a dozen extreme weather events across the globe last year. About half of the studies say human-caused climate change - due to the burning of fossil fuels and deforestation - contributed to the event examined.
Climate scientists often caution that no single weather event can be blamed on global warming, but Thomas Peterson of NOAA's National Climactic Data Center says that advances in climate modeling now allow them to "talk" about individual events.
"The models are improving," agrees Thomas Knutson of NOAA's Geophysical Fluid Dynamics Laboratory in Princeton, N.J., adding they're now able to simulate year-to-year climate patterns such as El Niño and La Niña and thus tease out the role of long-term global warming. The studies, edited by NOAA climate scientists, appear as a special supplement in today's Bulletin of the American Meteorological Society.
Knutson co-authored a study, based on historical data and 23 models, that estimates human-caused climate change contributed 35% to the extreme warmth that swept over the eastern USA from March through May last year. He says the risk of such an event occurring again is at least 10 times more likely.
Another study, led by NOAA's William Sweet, finds that coastal communities will see "increased frequency" of flooding akin to that in New Jersey and New York after 2012's Superstorm Sandy because of climate-induced sea level rise. "Events of less and less severity (from less powerful storms) will produce similar impacts," the study concludes.
Yet these researchers still say that typical weather and climate patterns played major roles in the extreme weather events studied. Diffenbaugh says lack of rainfall was a prime reason for last year's heat wave, and Knutson - like two French scientists who authored a similar study - sees natural variability as the main culprit in 2012's warm spring.
The NOAA-edited studies looked at twice as many extreme weather events worldwide - including Kenya's drought, southeast Australia's wetness and the Netherlands' cold spell - as did last year's compilation of similar research. Indeed, in the USA alone, 2012 brought 11 such events that each caused at least $1 billion in damage.
Diffenbaugh, whose research was federally funded, says understanding the likelihood that these disasters will reoccur can inform efforts to reduce vulnerability and quantify the true societal cost of greenhouse gas emissions.