As the globe warms from rising atmospheric concentrations of greenhouse gases, more moisture in a warmer atmosphere will make the most extreme precipitation events more intense, according to a newly-published NOAA-led study in Geophysical Research Letters.
The extra moisture brought on by a warmer atmosphere will lead to notable increases in precipitation rates, the researchers estimate.
The study also shows a 20-30% expected increase in the maximum precipitation possible over large portions of the Northern Hemisphere by the end of the 21st century if greenhouse gases continue to rise at a high emissions rate.
"We have high confidence that the most extreme rainfalls will become even more intense, as it is virtually certain that the atmosphere will provide more water to fuel these events," said Kenneth Kunkel, Ph.D., senior research professor at North Carolina State University's Cooperative Institute for Climate and Satellites and lead author of the paper.
Looking at three factors that affect maximum precipitation values – atmospheric moisture, upward motion of air, and horizontal winds – the team combined climate model data and greenhouse gas emissions projections to determine precipitation potential.
While greenhouse gas increases did not substantially change the maximum upward motion of the atmosphere or horizontal winds, the models did show a 20-30% increase in maximum moisture in the atmosphere, which led to a corresponding increase in the maximum precipitation value.
Percent maximum daily precipitation difference (2071-2100) - (1971-2000). NOAA photo.
The findings of this report could inform "design values" used by water resource managers, insurance and building sectors in modeling the risk due to catastrophic rain and snow events.
Engineers use the design value projections to best construct water impoundments and runoff control structures, such as dams, culverts, and detention ponds.
"Our next challenge is to translate this research into local and regional new design values that can be used for identifying risks and mitigating potential disasters. Findings of this study, and others like it, could lead to new information for engineers and developers that will save lives and major infrastructure investments," said Thomas R. Karl, L.H.D., director of NOAA's NCDC in Asheville, N.C., and co-author on the paper.
NOAA's National Climatic Data Center, the Desert Research Institute, University of Wisconsin-Madison, and ERT also contributed to the paper.
The study, Probable Maximum Precipitation and Climate Change, can be viewed online.