How much is climate change to blame for extreme weather?

This video was supported by funding from the Howard Hughes Medical Institute.

TRANSCRIPT

Maria Temming: In 2021, a historic heat wave baked the Pacific Northwest killing hundreds of people and fueling wildfires. Researchers later reported that human-caused climate change made this heat wave at least 150 times more likely.

But how do scientists figure out how much climate change is to blame for a specific weather event?

Researchers use a variety of techniques for this work, which is called extreme event attribution. One method compares the world we have today–which has warmed 1.2 degrees Celsius since the Industrial Revolution –with what the world would look like without climate change. Researchers estimate what that second world would look like based on historic trends in weather data and climate models.

Scientists can then see if a specific weather event is more likely or severe in the real world than it would have been in a world without climate change.
Another technique uses computer models to recreate specific weather events.

For instance, they might simulate how powerful a hurricane would have been, if Earth’s oceans were slightly cooler. If the hurricane would not have been as intense, that would suggest all the heat added to Earth’s oceans by global warming made the real-life hurricane worse.

Hundreds of studies have investigated the role of global warming in natural disasters around the world. And many have found that climate change made these events more likely or more severe.

Climate change tripled the risk of Hurricane Harvey’s record rainfall over Texas in 2017. It made Australia’s devastating wildfires in 2019 and 2020 at least 30 percent more likely. And in some cases, scientists have determined that a weather event would have been virtually impossible without climate change, such as a heat wave that cooked Siberia in 2020.

To do attribution studies like these, researchers typically need long-term weather data, models that can realistically simulate Earth’s climate in a certain area and a good understanding of the physical processes that drive extreme weather. This makes some types of extreme weather easier to study than others.

Heat waves are fairly easy to tie to climate change, because we have lots of long-term temperature records from around the globe, and computer models simulate temperature well.

It’s harder to pick out the fingerprints of climate change on heavy rainfall events in many parts of the world, because we have fewer long-term precipitation records, and computer models have a harder time rendering this weather.

Meanwhile, tornadoes are typically too small to directly simulate with existing climate models.

And individual wildfires are especially hard to link to climate change, because they depend on many non-weather factors, like land management. Large parts of the world, including regions in Africa and South America, don’t have the long-term weather records or region-specific climate models to do attribution studies.

So we need more data and better models to better understand how climate change is affecting weather in those areas.

This type of research doesn’t just underscore how climate change is already impacting our daily lives, it can offer clues about the types of weather we should expect and prepare for as our world continues to warm.