Heavy rain combined with melting snow can be a destructive combination.
In mid-June 2022, storms dumped up to 5 inches of rain over three days in the mountains in and around Yellowstone National Park, rapidly melting snowpack. As the rain and meltwater poured into creeks and then rivers, it became a flood that damaged roads, cabins and utilities and forced more than 10,000 people to evacuate.
The Yellowstone River shattered its previous record and reached its highest water levels recorded since monitoring began almost 100 years ago.
Although floods are a natural occurrence, human-caused climate change is making severe flooding events like this more common. I study how climate change affects hydrology and flooding. In mountainous regions, three effects of climate change in particular are creating higher flood risks: more intense precipitation, shifting snow and rain patterns and the effects of wildfires on the landscape.
Warmer air leads to more intense precipitation
One effect of climate change is that a warmer atmosphere creates more intense precipitation events.
This occurs because warmer air can hold more moisture. The amount of water vapor that the atmosphere can contain increases by about 7% for every 1.8 degrees Fahrenheit (1 degree Celsius) of increase in atmospheric temperature.
Research has documented that this increase in extreme precipitation is already occurring, not only in regions like Yellowstone, but around the globe. The fact that the world has experienced multiple record flooding events in recent years—including catastrophic flooding in Australia, Western Europe and China—is not a coincidence. Climate change is making record-breaking extreme precipitation more likely.