Using a four-pronged framework, Professor of Earth System Science Noah Diffenbaugh ’96 M.S. ’97 and his research team have found a direct connection between extreme weather events and human impact.  

The team’s study, published in the Proceedings of the National Academy of Sciences magazine, outlines an objective approach to determining whether or not extreme weather events – such as the flooding in northern India in June 2013 or the slowly-subsiding California drought that began in 2012 – can be linked to climate change over the course of several years. The researchers discovered that, for a substantial number of recent extreme weather cases, there is indeed a connection.

“Our results suggest that the world isn’t quite at the point where every record hot event has a detectable human fingerprint, but we are getting close,” Diffenbaugh stated in an interview with Stanford News.

While scientists have historically avoided directly linking specific extreme weather events to climate change due to the variability of weather, according to Diffenbaugh and his research team, it is more important than ever to determine global warming’s role in causing record-breaking events.

The study’s multi-pronged approach reveals not only surface-level weather conditions but also underlying meteorological phenomena that contribute to these events.

The team analyzed climate change observations with advanced statistical models, a framework which the researchers say can be used to inform decisions in fields as diverse as farming, insurance and infrastructure.

With this framework, the researchers found that global warming from human emissions has made extreme hot weather events more likely across over 80 percent of the areas of the globe for which observations are possible.

“Our approach is very conservative,” Diffenbaugh said. “It’s like the presumption of innocence in our legal system: The default is that the weather event was just bad luck, and a really high burden of proof is required to assign blame to global warming.”

Contact Ellie Bowen at ebowen ‘at’ stanford.edu.