Pick your poison: deluge or drought?

This year, the central United States is in the grip of the worst drought in decades.

Last year, the heaviest snow and rain runoff in more than a century created historic flooding along the Missouri River.

An advocacy group, Environment America Research & Policy Group, and a think tank, the Frontier Group, published a study Tuesday that chronicles the increase in extreme precipitation that has occurred in the United States from 1948 through 2011.

Extreme rains and snows occur in a warming world for two reasons, the study finds:

- Warm air can hold more moisture than cold air (think of hot, humid summers and cold, dry winters).

- Hotter weather leads to greater evaporation and more moisture in the atmosphere.

As a result, scientists say, the amount of moisture in the atmosphere is rising by 1.3 percent per decade.

With more moisture in the air, large rain and snowstorms are occurring 30 percent more often nationwide than they were in 1948, according to the study.