There's a good chance that you have experienced unusual or even dangerous weather in recent years if you are a human being. Perhaps it was a heatwave that was longer and hotter than you have ever seen. A thunderstorm that dumped a frightening amount of rain. A powerful hurricane that appeared to form overnight.
Climate change is a part of this story. As the Earth heats up, extreme weather becomes more common. However, such broad statements can seem impersonal. What you really want to know is: Has climate change affected my life?
"You've had an extreme weather event, and people want the following: Did climate change flood your house? Is climate change causing it to be so hot that my power went off? Michael Wehner is a senior scientist at Lawrence Berkeley National Laboratory, who studies the effects of climate change on extreme weather. These are great questions.
Scientists can now answer these questions with greater certainty. It's now possible to determine how much the climate change has made certain weather worse. Or that the catastrophe would never have occurred if global warming had not been for it.
Every heat wave is made worse by climate change
Global warming is most closely linked to heat waves. Wehner states, "It seems clear that as the global temperature warms, heat waves will also warm."
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How much warmer is it, though?
Scientists have measured this. Wehner explained that "for garden variety heat waves, aEUR", like the hottest days of the year or the hottest 10 years, aEUR") in the U.S.A, climate change has caused that heat wave to heat up by 3 to 5 degrees Fahrenheit."
When heat records are broken repeatedly, you can see the extra degrees in action. Millions of people in over a dozen cities across the West U.S. and Texas were able to experience record-breaking heat waves this June. Phoenix, Las Vegas, and Houston set heat records almost every summer.
Scientists can even go further by using supercomputers to analyze extreme heat waves. This includes the one that claimed the lives of hundreds in Canada and the Pacific Northwest in 2021. In parts of Canada, temperatures reached 120 degrees and in Washington and Oregon it hit 115 degrees.
Scientists discovered something surprising when they looked at how climate change affected the heat wave. Wehner says, "It was practically impossible without climate change."
Another way to put it? Extreme heat waves last summer were caused by climate change.
Statistics is the most common language used by scientists to communicate their ideas. This has its upsides as well as downsides.
Climate scientists avoid the use of the term "cause". Instead, they prefer numbers that show how likely extreme weather events were in a world without humans using large amounts of fossil fuels.
However, scientists know that these numbers may not be meaningful to the general public.
"We could easily say that the 2021 Pacific Northwest heatwave was an 1 in 1000 year event in our climate today. It was 150 times more likely in today's climate than in preindustrial climates, says Luke Harrington, senior research fellow at Victoria University of Wellington in New Zealand, who studies extreme weather and climate change. But that's not helpful if you want to understand why the heat wave was not happening in a preindustrial environment.
Wehner points out the importance of detailed numbers for dangerous weather types. They tell people how often they will need to deal with them.
Imagine a storm that rains more than usual and floods your home. This type of storm was rare in the past. It would only happen once in a while.
Scientists may be able to study the storm and determine that climate change made it 10 times more likely.
Wehner explains that if an event is 10x more likely it means that it will happen once in seven years, instead of once per lifetime. Weather that was once rare is now commonplace. This knowledge can be used to plan for the future.
Future weather forecasts may include climate change information
These research methods are quite new in the grand scheme of things. In general, science moves slowly. Science is slow. However, the science of finding climate fingerprints within individual weather disasters has grown from infancy and matured in 20 years. This is partly due to the huge demand for information on how global warming affects our lives.
Wehner says that there is a demand from the public for these services. According to Wehner, the research techniques are so advanced that even people with no academic training can do the work. He explains that this could be done in the same way as weather forecasting.
This service would allow for analysis of how climate change has affected individual weather events in Europe. It is currently being piloted by the European Union's satellite weather service.
This would allow climate scientists to spend their time addressing the most urgent questions about global warming and extreme weather.
Scientists can't study certain types of weather.
Scientists are still unable to determine the impact of climate change on specific weather events because they are complex.
Finally, climate change is also a factor in this #heatwave. The most well-known fact in attribution science is the increasing frequency, duration, and intensity of heatwaves associated with global warming. pic.twitter.com/V27Hmn9Hog
As the Earth heats up, wildfires become more common and more intense. Global warming causes soil to dry out and makes it more common for hot and dry weather.
Scientists aren't in a position to determine how likely or worse a wildfire is due to global warming.
This is partly due to the fact that humans can be so active in determining where and how big fires go. Wildfires are usually started by humans. The amount of vegetation, such as grass, trees and shrubs, that can be used to fuel the fire is determined by human land management. Firefighters also have an impact on how big and where the fire burns.
Megan Kirchmeier–Young, a researcher at Environment and Climate Change Canada, says that fires have many different factors and only a few of them are directly related to climate. She studies extreme weather.
It is difficult to attribute individual hurricanes to climate changes. Hurricanes are complex and rarer than other extreme weather types aEUR", especially because only a fraction of storms that form make it to land.
This small data set makes it difficult for us to compare storms today with global warming to storms that occurred before global warming.
Scientists are still able to quantify the impact of climate change on hurricane rainfall in some cases. Climate change was responsible for up to 15% more rainfall during Hurricane Harvey 2017. Another study examined the entire 2020 hurricane season. It found that climate change had increased extreme rainfall by 10%.
Researchers are still trying to figure out how climate change can cause other changes in hurricanes. Jill Trepanier is a researcher at Louisiana State University who studies climate change as well as tropical cyclones.
Hurricanes are becoming more powerful and storms are likely to intensify more quickly. Both phenomena are generally due to warmer ocean water. However, scientists don't know enough about the science to determine if a particular storm is "x" percentage stronger or intensified "y%" faster because of climate change.
"We cannot say that this is why they intensify rapidly." She says that we haven't solved this problem. "That's something that we're still working towards."
