Global Warming

Half of the Year's Rain Falls on Earth in Just 12 Days

It takes less than two weeks for half of the planet's annual precipitation to fall. That is, 50 percent of Earth's rain, snow and ice each year falls in the 12 wettest days, according to a new study. The deluges are likely to become even more concentrated by the end of the century, researchers reported Oct. 19 in the journal Geophysical Research Letters.

What the researchers found is that the expected increases happen when it's already the wettest — the rainiest days get rainier.

Climate scientists have long been concerned that the increase in global average temperatures will cause weather events that are more extreme. Warmer air can hold more moisture, and a different study, published Nov. 14, found that today's hurricanes are already wetter due to climate change.

Already, most of the water that falls from the sky does so in a mind-bogglingly short period of time. It takes just 12 days to account for half the world's yearly annual precipitation, the researchers reported.

The scientists found that a whopping 75 percent of the world's precipitation falls in approximately a month's time (the wettest 30 days, spread across the year). Twelve and a half percent of annual precipitation falls in just two days. And the wettest single day of the year accounts for 8.3 percent of the year's total.

Regionally, this tendency for a lot of wetness in only a short period of time is most obvious in dry, desert environments, the researchers found. China and southeastern Russia are right in the middle, and "wet" places like the northeastern United States show the most even distribution of precipitation.

Globally, the wettest day of summer accounts for 5.2 percent of the year's precipitation, while the wettest day of winter is a little drier, at 3.4 percent of the annual precipitation budget.