Climate Crisis Will Bring Drought In Temperate Areas, Fnds NASA
5 May, 2013
Climate crisis may increase the risk of extreme rainfall in the tropics and drought in temperate zones. Citing a new study led by NASA Neela Banerjee reported  from Washington:
"These results in many ways are the worst of all possible worlds," said Peter Gleick, a climatologist and water expert who is president of the Pacific Institute, an Oakland research organization. "Wet areas will get wetter and dry areas will get drier."
The regions that could get the heaviest rainfall are along the equator, mainly over the Pacific Ocean and the Asian tropics. Increased aridity and drought could have a greater effect on human life, however, because those conditions are more likely to occur where most of the world's population lives.
In the Northern Hemisphere, drought-prone areas include the southwestern US, Mexico, North Africa, the Middle East, Pakistan and northwestern China. In the Southern Hemisphere, drought could become more likely in South Africa, northwestern Australia, coastal Central America and northeastern Brazil.
"Large changes in moderate rainfall, as well as prolonged no-rain events, can have the most impact on society because they occur in regions where most people live," said William Lau, the study's lead author and a scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "The regions of heavier rainfall, except for the Asian monsoon, may have the smallest societal impact because they usually occur over the ocean," he added.
The study is based on the results of 14 models that show agreement on the possible rainfall trends, Gleick said.
Climate change does not cause forest fires but does contribute to their likelihood, Gleick said, adding: "It's not about causality but influence."
For every 1 degree Fahrenheit increase in global average temperature because of GHG emissions, heavy rainfall will increase globally by 3.9%, the study predicted.
Climate change could lead to heavier rainfall because warmer air holds more moisture.
On the flip side, for every degree Fahrenheit of warming, the length of time a region goes without rain could increase globally by 2.6%.
Scientists have said that the world needs to keep global average temperatures from exceeding 2 degrees Celsius, or about 3.6 degrees Fahrenheit, above pre-industrial global temperatures to avert catastrophic changes to nearly all aspects of life. In the last 150 years or so, the Earth's average temperature has already risen about 1 degree Celsius, or 1.3 degrees Fahrenheit.
To prevent the 2 degree Celsius rise and its effects, including extremes in rainfall, the world has to keep emissions of heat-trapping carbon dioxide below a ratio of 400 parts per million.
According to the Scripps Institution of Oceanography at UC San Diego, there have been isolated measurements of 400 parts per million in the Arctic, and scientists expect readings in Hawaii to exceed 400 parts per million this month.
Another report  added:
The study, to be published in the journal Geophysical Research Letters, demonstrates for the first time how rising carbon dioxide concentrations could affect the entire range of rainfall types on Earth.
“In response to carbon dioxide-induced warming, the global water cycle undergoes a gigantic competition for moisture resulting in a global pattern of increased heavy rain, decreased moderate rain, and prolonged droughts in certain regions,” said William Lau.
Light rain will also increase by one percent, across the globe. Because moderate rainfall is projected to decrease by 1.4 percent, total global rainfall is not expected to change much.
Scientists define heavy rainfall as months that receive an average of more than about 0.35 of an inch per day, and light rainfall as months that receive an average of less than 0.01 of an inch per day. The definition of moderate rainfall is months that receive an average of between about 0.04 to 0.09 of an inch per day.
According to the study, some regions outside the tropics may have no rainfall at all.
The researchers calculated statistics on the rainfall responses for a 27-year control period, starting at the beginning of the simulation. They also calculated statistics for 27-year periods around the time of doubling and tripling concentrations.
Predictions for how much rainfall will occur at any one location as the climate warms are not very reliable, the team found.
“But if we look at the entire spectrum of rainfall types we see all the models agree in a very fundamental way — projecting more heavy rain, less moderate rain events, and prolonged droughts,” Lau said.
 Los Angeles Times, May 4, 2013,
Climate change may bring drought to temperate areas, study says,
 Red Orbit, May 4, 2013, “Rain And Drought Will Increase Due To Warming: NASA”,
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