What's driving the increase in extreme weather events?

The main long-term driver is human-caused warming, largely from burning fossil fuels and changes in land use. But “extreme weather” covers many different events, and the trend is not identical for every type or region.

A warmer atmosphere holds more moisture and adds energy to the climate system. That raises the odds of some extremes:

• Heat waves are more frequent and intense in most regions.
• Heavy rainfall has become more likely in many places because warmer air can carry more water vapor, although local patterns vary.
• Some regions face greater risk of severe agricultural or ecological drought, especially where higher temperatures dry out soil and vegetation.
• Warmer oceans and higher sea levels can worsen the rainfall and coastal flooding associated with some tropical cyclones. Evidence for a global increase in the number of cyclones is less clear than evidence for stronger rainfall and a greater share of intense storms.

Natural climate variability still matters. El Niño, ocean cycles, and local weather patterns can make a particular year or place unusually wet, dry, hot, or stormy. They influence when and where extremes occur; long-term warming shifts the odds and can intensify some events.

There is also a difference between an increase in hazardous weather and an increase in reported disasters. More people and infrastructure in exposed areas, along with better monitoring and reporting, can raise losses and recorded event counts. Those factors affect impacts and records, but they do not explain the observed warming-driven changes in many types of extreme weather.