NASA study projects warming-driven changes in global rainfall (w/ Video)

May 03, 2013 by Kathryn Hansen

(Phys.org) —A NASA-led modeling study provides new evidence that global warming may increase the risk for extreme rainfall and drought.

The study shows for the first time how rising could affect the entire range of types on Earth.

Analysis of computer simulations from 14 climate models indicates wet regions of the world, such as the equatorial Pacific Ocean and Asian monsoon regions, will see increases in heavy precipitation because of warming resulting from projected increases in carbon dioxide levels. Arid land areas outside the tropics and many regions with moderate rainfall could become drier.

The analysis provides a new assessment of global warming's impacts on around the world. The study was accepted for publication in the journal Geophysical Research Letters.

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Model simulations spanning 140 years show that warming from carbon dioxide will change the frequency that regions around the planet receive no rain (brown), moderate rain (tan), and very heavy rain (blue). The occurrence of no rain and heavy rain will increase, while moderate rainfall will decrease. Credit: NASA's Goddard Space Flight Center Scientific Visualization Studio

"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 of NASA's Goddard Space Flight Center in Greenbelt, Md., and lead author of the study.

The models project for every 1 degree Fahrenheit of carbon dioxide-induced warming, heavy rainfall will increase globally by 3.9 percent and light rain will increase globally by 1 percent. However, total global rainfall is not projected to change much because moderate rainfall will decrease globally by 1.4 percent.

Heavy rainfall is defined as months that receive an average of more than about 0.35 of an inch per day. Light rain is defined as months that receive an average of less than 0.01 of an inch per day. Moderate rainfall is defined as months that receive an average of between about 0.04 to 0.09 of an inch per day.

Areas projected to see the most significant increase in heavy rainfall are in the tropical zones around the equator, particularly in the Pacific Ocean and Asian monsoon regions.

Some regions outside the tropics may have no rainfall at all. The models also projected for every degree Fahrenheit of warming, the length of periods with no rain will increase globally by 2.6 percent. In the Northern Hemisphere, areas most likely to be affected include the deserts and arid regions of the southwest United States, Mexico, North Africa, the Middle East, Pakistan, and northwestern China. In the Southern Hemisphere, drought becomes 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," Lau said. "Ironically, the regions of heavier rainfall, except for the , may have the smallest societal impact because they usually occur over the ocean."

Lau and colleagues based their analysis on the outputs of 14 in simulations of 140-year periods. The simulations began with carbon dioxide concentrations at about 280 parts per million—similar to pre-industrial levels and well below the current level of almost 400 parts per million—and then increased by 1 percent per year. The rate of increase is consistent with a "business as usual" trajectory of the greenhouse gas as described by the United Nations' Intergovernmental Panel on Climate Change.

Analyzing the model results, Lau and his co-authors calculated statistics on the rainfall responses for a 27-year control period at the beginning of the simulation, and also for 27-year periods around the time of doubling and tripling of concentrations. They conclude the model predictions of how much rain will fall at any one location as the climate warms are not very reliable.

"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.

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User comments : 9

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VENDItardE
1.4 / 5 (20) May 03, 2013
alarmist BS
VendicarE
4.2 / 5 (10) May 03, 2013
VendiTardE is accusing a series of differential equations as having alarmist intentions.

I had no idea that differential equations were capable of spontaneous thought.

On the other hand we know from experience, that VendiTardE has no such capacity.
Neinsense99
2.2 / 5 (13) May 03, 2013
VendicarE, you must live in one of those safe upper class areas of intellectual discourse where the logic police actually respond. Down here, I'm not only suspicious of differential equations with nefarious intent when I see them being solved on the other side of the street, I know several people who've been mugged by those mathematical hooligans.
deepsand
3 / 5 (18) May 03, 2013
alarmist BS

TROLL
mountain_team_guy
1.7 / 5 (18) May 04, 2013
Regardless of whether global warming causes increased or decreased rainfall, increased or decreased temperatures, there undoubtably will be a study backed by legions of 'scientists' who declare it will be 'extreme'. It's too predictable, uniformly boring, and totally contrary to my personal observations. Those observations being decades of global travel. Currently I'm staring across the Himalaya from the Ganesh range to Gauri Shankar. The only real change I see is the dramatic improvement in the Nepalese economy. Sure didn't come from carbon credits. Don't see any big effects back home in the Cascades. Don't see any changes in Texas. Korea looks good. Thailand looks better. So, keep the propaganda coming. As soon as the drama matches observations, I'll be able to see past the agenda.
antigoracle
1 / 5 (15) May 05, 2013
I had no idea that differential equations were capable of spontaneous thought.

Obviously, neither is the AGW Alarmist Turd.
deepsand
2.9 / 5 (15) May 05, 2013
I had no idea that differential equations were capable of spontaneous thought.

Obviously, neither is the AGW Alarmist Turd.

It comes as no surprise to see that that went right over your head. :rolleyes:
Neinsense99
2.6 / 5 (10) May 26, 2013
VendicarE, you must live in one of those safe upper class areas of intellectual discourse where the logic police actually respond. Down here, I'm not only suspicious of differential equations with nefarious intent when I see them being solved on the other side of the street, I know several people who've been mugged by those mathematical hooligans.


(Sarcasm sensors seem to be malfunctioning here...)
Neinsense99
2.3 / 5 (9) May 26, 2013
I had no idea that differential equations were capable of spontaneous thought.

Obviously, neither is the AGW Alarmist Turd.

Sarcasm seems as above him as irony.