When a devastating heat wave, hurricane, flood or wildfire strikes, people often want to know: How much did human-caused climate change influence this event, if at all?

For many years, scientists could answer that question only in general terms. They knew that human-caused climate change was increasing the frequency or intensity of some kinds of extreme weather, but determining its influence on a particular event was much more difficult.

Today, researchers can provide a scientifically grounded answer that assesses whether climate change made a heat wave hotter, increased rainfall from a hurricane, or made a drought more severe. But the answers are not always straightforward, and they are not equally certain for every type of extreme event.

We served on the 14-member National Academies of Sciences, Engineering, and Medicine committee that produced a new report that reviewed where this rapidly developing field, known as extreme event attribution, stands today.

The report concludes that advances in weather and climate data, climate models and attribution methods have substantially strengthened scientists’ ability to assess the influence of climate change on many types of extreme events, while also identifying important scientific limitations.

How can scientists study a single event?

Weather events result from many interacting factors, including the day-to-day state of the atmosphere.

Scientists conducting extreme event attribution studies aren’t asking whether climate change caused a hurricane, heat wave or flood. Instead, they’re asking how climate change influenced that event: How would this event have differed in a world without increased greenhouse gases, and how have the chances of it occurring been altered by warming?

Researchers answer that question using two complementary approaches:

One compares how often that type of event, for example an extreme downpour that causes flooding, occurs in today’s climate with how often it would have occurred in a climate........

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