Why are ‘100-year storms’ happening so often?

CLIMATE CHANGE IS LEADING NOT ONLY TO DROUGHTS, wildfires, and extreme weather. It's also leading to oxymorons—at least when it comes to what are known as 100-year storms, floods, and other events.

- JEFFREY KLUGER

Climate change is heating up the atmosphere, leading to extreme weather

Long-term weather forecasting is all about probabilities, factoring together not only current conditions and trends, but also the historical record. Environmental scientists have gotten so good at reading weather history that they can characterize some severe storms or floods as likely to occur in a given area only once in 100 years—or even 500 years or 1,000 years.

That's where the oxymoron comes in. As climate change leads to greater meteorological volatility, the events forecast to happen once in 100—or 500 or 1,000—years are occurring twice or three times or more in those windows. Since 1999, there have been nine storms along the North Carolina coast that qualify as 100or 1,000-year events. One study by the Montreal-based carbon-removal project Deep Sky calculates that the frequency of deadly hurricanes has jumped 300%, with “100-year storms” now forecast to occur once every 25 years.