Risk of record heat now four times what it was in pre-industrial times, finds study

According to a study presented in the American Meteorological Society report titled Explaining Extreme Events of 2012 from a Climate Perspective, climate change has created conditions that make record temperatures four times more likely than what was experienced before the industrial revolution.

The study, performed by researchers at Stanford University, specifically looked at the record temperatures seen in the United States in July of 2012 (what they called 'The Event'), which was the hottest month ever recorded.

First, looking at how July 2012 stacked up against the weather recorded between the years 1979 and 2011. They created maps to show just how 'extreme' the month was, and how much of an 'anomaly' it was compared to the weather in that 32 year period. Then, using three different computer models, they figured out how often these kinds of events would happen, both in pre-industrial times (prior to us dumping massive amounts of CO2 into the atmosphere) and now, with the current conditions.

They found that July 2012 was at least a 100-year-event, but with conditions as they are now (what they call 'current forcing'), for the regions from the U.S. Midwest through to the Northeast, extreme 'July-2012-like' weather events are four times more likely now than they were before industrial times.

"Going forward, if we want to understand and manage climate risks, it's more practically relevant to understand the likelihood of the hazard than to ask whether any particular disaster was caused by global warming," Noah Diffenbaugh, a senior fellow at Stanford's Woods Institute for the Environment, said in a statement.

"Knowing how much our emissions have changed the likelihood of this kind of severe heat event can help us to minimize the impacts of the next heat wave, and to determine the value of avoiding further changes in climate," Diffenbaugh added.

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The research by Diffenbaugh and research assistant Martin Scherer is just one peer-reviewed study of the larger AMS report, which examines many of the extreme weather events from around the world in 2012, to see if they can be linked to human activities. The overall conclusions of the report were that of the 12 events studied, natural fluctuations in weather and climate played a roll, but "approximately half of the analyses found some evidence that anthropogenic climate change was a contributing factor to the extreme event examined."

(Photo courtesy: John Sommers II/Reuters)

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