How Science Links Global Warming to Extreme Weather
(Bloomberg) -- As long as climate change has been a topic of public discussion, one question has been whether a warming globe makes extreme weather events worse. A new branch of science has emerged in the past few years that finally can offer some answers. Although precise connections between warming trends and extreme weather aren’t completely understood, this growing field of study connects climate change and greater risks of deadly hurricanes, typhoons, rainstorms, wildfires, heat and even cold.
1. What extreme weather is most tied to climate change?
Heat waves are the weather events most directly linked to humanity’s greenhouse gas pollution. And heat, along with drought and wind, fuels forest fires, which is why scientists have become so confident that climate change is making wildfires in the western U.S., Australia and elsewhere much worse. (The U.S. fire season is two months longer than it was in the 1970s and 1980s.) Global warming’s connection to hurricanes, in terms of both frequency and severity, is harder to pin down, given their meteorologically complex nature and how quickly they form and dissipate. But warmer water and moister air -- two results of global warming -- provide added fuel to tropical cyclones and other storms, which are expected to become more intense as the century wears on.
2. How certain is the link?
Carbon Brief, a U.K.-based nonprofit that covers developments in climate science, reviewed studies of more than 400 extreme weather events, the vast majority of them since 2011, to see whether they could be attributed to human-caused climate change. (This field is known as extreme event attribution.) The review found that 70% of the extreme weather events were more likely to occur, or were made more severe, because of global warming.
3. How is cold weather connected?
Studies reviewed by Carbon Brief tended to find that climate change had made blizzards and extreme cold snaps less likely, rather than more. But that doesn’t mean the warming globe has no impact on cold weather. Earth’s poles are warming faster than elsewhere, with the North Pole heating up about twice as fast as the rest of Earth for the last 30 years. This has caused a decrease in the contrast between the heat of the equator and the cold of the North Pole, and that has consequences. The record cold that crippled the Texas power grid in February 2021, for example, was the result of the polar vortex -- a girdle of winds that typically keeps cold bottled in the Arctic -- buckling and releasing cold air across much of the U.S.
4. What are other recent examples of extreme weather?
Floods in Germany and Belgium killed more than 200 people in June 2021. That same month, the British Columbia town of Lytton set Canada’s all-time high temperature -- 49.6 degrees Celsius (121.3 degrees Fahrenheit) -- a day before wildfires destroyed it. Brazil and Argentina struggled with severe droughts in 2021, and wildfires devastated Australia in 2019 and 2020. The Atlantic Ocean produced an all-time high of 30 hurricanes and tropical storms in 2020, and two of the strongest hurricanes ever to hit the U.S. Gulf Coast, as measured by windspeed at landfall, were Laura in 2020 and Ida in 2021. Vast areas of the American West have been consumed by wildfires in recent years, including parts of Oregon and Washington that were once too wet to produce the required dry brush as fuel.
5. Where is this headed?
Humanity has raised global average temperatures by 1.1 degrees Celsius since the end of the 19th century, according to the United Nations Intergovernmental Panel on Climate Change, or IPCC. At the current pace, that increase will reach 1.5 degrees -- the level at which global warming becomes extra dangerous, in the view of climate scientists -- as soon as the 2030s. From there, the intensity of extreme weather grows exponentially, doubling if global warming reaches 2 degrees and quadrupling at 3 degrees, the IPCC says.
6. What are the ramifications?
More than 5 million people die each year globally because of excessive temperatures, and deaths tied to heat in particular are rising, according to a study in the Lancet Planetary Health. Climate change is affecting many financial calculations, since huge parts of the global economy including agriculture, travel and insurance face risks tied to the weather. Insurers were hit by $89 billion of losses from disasters in 2020, the fifth-costliest year for the industry in data going back five decades, according to Swiss Re. The bulk of those costs were from natural catastrophes, including hurricanes Laura and Sally.
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