As floodwaters from the swollen River Thames crept closer to the walls of Myles Allen’s south Oxford home in the United Kingdom, he was thinking about climate change—and if scientists could figure out if it was affecting the climbing water outside.
It was January 2003, and as Allen—a climate expert at the University of Oxford—monitored the rising waters from the safety of his house, a voice on the radio was telling him that it couldn’t be done. Sure, the flood was the type of event likely to be made more frequent by global warming, the representative of the United Kingdom’s Met Office said on the show. But ascertaining anything more concrete was out of reach.
At the time, the Thames River Basin had seen some of its greatest rainfall in decades, and by early January, the flow in some parts of the river was the highest it had been since 1947.
But the radio voice added that it would be “impossible to attribute this particular event [floods in southern England] to past emissions of greenhouse gases,” said Allen in a commentary published in Nature shortly thereafter.
In 2003, that was the predominant view in the scientific community: While climate change surely has a significant effect on the weather, there was no way to determine its exact influence on any individual event. There are just too many other factors affecting the weather, including all sorts of natural climate variations.
But Allen wasn’t so sure.
“At the time, everybody was saying, ‘Well, you can’t attribute a single event to climate change,'” he said in an interview with E&E News. “And this prompted me to ask, ‘Why not?'”
So he drafted his commentary as the floodwaters inched closer to his kitchen door. He wrote that it might not always be impossible to attribute extreme weather events to climate change—just “simply impossible at present, given our current state of understanding of the climate system.” And if researchers were ever able to make that breakthrough, he mused, the science could potentially influence the public’s ability to blame greenhouse gas emitters for the damages caused by climate-related events.
His hunch held true. Nearly 15 years later, extreme event attribution not only is possible, but is one of the most rapidly expanding subfields of climate science.
“The public stance of the scientific community about individual event attribution in the year 2000 is that it’s not something that science does,” said Noah Diffenbaugh, a Stanford University climate scientist and attribution expert. “And so to go from that to now, that you’ll find a paper every week … that’s why we say there’s been an explosion of research. It’s gone from zero to 60, basically.”
Over the last few years, dozens of studies have investigated the influence of climate change on events ranging from the Russian heat wave of 2010 to the California drought, evaluating the extent to which global warming has made them more severe or more likely to occur.
The Bulletin of the American Meteorological Society now issues a special report each year assessing the impact of climate change on the previous year’s extreme events. Interest in the field has grown so much that the National Academy of Sciences released an in-depth report last year evaluating the current state of the science and providing recommendations for its improvement.