Four days and four hours after a powerful storm battered parts of the U.K. last December—breaking national records and leaving 5,000 homes flooded—researchers made a statement: The unusually heavy rain was linked to climate change.
Last July, when temperatures topped 104 degrees in several European countries, breaking more records, scientists also quickly analyzed the data as the heat wave happened. They concluded that the extreme temperatures were much more likely now than in the past because of climate change. In Zurich, for example, the heat wave was roughly 8 times more likely now than in 1900.
Neither are statements scientists might have made in the past. If someone asked what climate change had to do with the weather on any particular day, the answer might have been it wasn't possible to make the link for a specific storm or extreme weather event. Early climate research was focused on long timespans—what might change by the end of the century. But science has evolved so much, that this is no longer true.
"Originally we could only look at large areas over very long periods of time," says Heidi Cullen, chief scientist for Climate Central and one of the authors of a new report on climate attribution. "Now we've really been able to shrink everything down, so we can perform an autopsy, if you will, on individual events."
It's also possible to do the analyses in real time, as weather unfolds—and to share that data right away, while the public is still interested.
"What we saw playing out in the media landscape was that in the aftermath of an extreme event, there were so many questions being asked about the possible role of climate change, and our feeling was that a lot of times the answers that were given were not based in objective science," says Cullen. But she says that technologies and methodologies are available to answer these questions rigorously and quickly—without the standard year-long peer review process, so that the news story is still fresh on people's minds.
When the researchers made a statement about the heavy storms in the U.K., they also released it to an open-source journal, so anyone can review and analyze the process. They also used multiple techniques—regional and global modeling—to have as much confidence as possible in their answer.
It's easier to link some types of weather with climate change—such as extreme heat or cold, droughts, or massive storms—than others, like wildfires or tornadoes. "We know that wildfire risk is going to increase," Cullen says. "It's just very hard for us at this point to untangle the role climate change played in an individual wildfire. Whereas with an individual heat wave or cold wave, heavy rainfall or drought, we actually have some really solid techniques to do that."
The studies don't say climate change causes extreme weather, since there are multiple factors at play. But just like it's possible to say smoking increases the risk of lung cancer, it's now possible to say climate change increases the risk of heat waves and floods. One recent study in Australia found that an extreme heat wave last year was 23 times more likely because of climate change. Floods in 2013-2014 in the U.K. were 40% more likely because of climate change. And the list goes on.
That has big implications for insurance companies (natural disasters cost the world $90 billion in 2015, including $27 in insured losses), and for urban planning. "There's tremendous existential risk associated with climate change," says Cullen. "Everything from ocean acidification, coral bleaching, species loss, tremendous sea level rise—but the most immediate impacts, and in many cases the most costly effects that we're going to see right now are going to be from the changing risks associated with extreme weather...Extreme weather is something that we have to deal with."