As the globe continues to warm, the rainiest parts of the world are very likely to get wetter, according to a new study in Science. Desert dwellers, however, are likely to see what little rain they receive dry up, as the rain becomes even more concentrated in high-precipitation areas.

Atmospheric scientists Richard Allan of the University of Reading in England and Brian Soden of the University of Miami looked at satellite records of daily rainfall stretching back to 1987 to see how warmer temperatures had affected precipitation. That's one of the key climate changes expected from rising greenhouse gas levels in the atmosphere. The researchers specifically focused on El Niño, the warming of the waters of the tropical Pacific that raises air pressure,  changes winds, and recurs every few years.

The weather pattern causes floods in some areas and droughts in others while changing climate across the globe over time—and thus is a pretty good stand-in for global warming.

"For the period we examined, 1987 to 2004, there was a clear relationship between warm El Niño events and increased occurrence of heavy precipitation," Soden says. Such "events will certainly become more frequent in a warmer climate."

For example, other research has shown that monsoon storms that dump six inches (150 millimeters) or more of rain on India have become more common since the 1950s.

The satellite observations agree with the predictions of various computer models. The U.N. Intergovernmental Panel on Climate Change expects that such changes will wreak havoc on agriculture, human health and the natural environment.

But the Science study also reveals that the computer projections may be underestimating how severe such downpours may become. Warmer seas resulted in three times as many heavy rainstorms as the models would have predicted—and other studies have shown that such models fail to account for the rapid increase in water vapor in the atmosphere.

"It is very likely that heavy rainfall will become more common and more intense in a warming world," Allan says. "It is too early to say by how much real world changes in rainfall will surpass projections from the climate models."

7 Comments

1. 1. srchuck 11:19 AM 8/8/08

   Admitting the climate models cannot accurately predict either rainfall or water vapor in the atmosphere, but holding fast to the fantasy that they can accurately predict warming, in the same article, no less?

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2. 2. pat n 04:12 PM 8/8/08

   From Chanhassen

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3. 3. pat n 04:21 PM 8/8/08

   Rainfall intensity has been increasing in the Midwest.

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4. 4. zetalimit 07:33 AM 8/11/08

   I^mz .... I = infinite ^ angle of mz = largest and smalles measurement programmed ga programming infinite global var; this works with a-z in science like earth = e3 = mc

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5. 5. Pat O'Green 01:02 PM 8/11/08

   Its still counter intuitive to me that CO2 which absorbs less heat than water vapour can have a significant effect on global warming. The amount of water vapour in the air at any time must be orders of magnitudes greater than the amount of CO2 so how does CO2 have an impact? In addition water vapour scrubs the CO2 from the atmosphere and it is deposited in the sea. Then becoming trapped in the photosynthesis cycle or as carbonates. Global warming appears to be happening, but maybe its causes are not CO2.

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6. 6. Bamboo 01:40 PM 8/11/08

   The earth is our life. It will be over someday. But we can delay it.

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7. 7. pat n 10:32 AM 8/12/08

   "While water vapour is indeed the most important greenhouse gas, the issue that makes it a feedback (rather than a forcing) is the relatively short residence time for water in the atmosphere (around 10 days)."
   
   http://www.realclimate.org/index.php?p=142
   
   The volume of CO2 in the atmosphere is increasing:
   
   "The annual mean rate of growth of CO2 in a given year is the difference in concentration between the end of December and the start of January of that year." See 2nd figure a link below.
   
   http://www.esrl.noaa.gov/gmd/ccgg/trends/

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