Global Warming

NASA Study Projects Warming-Driven Changes In Global Rainfall

A NASA-led 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 carbon dioxide concentrations could affect the entire range of rainfall 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 precipitation patterns around the world. The study was accepted for publication in the American Geophysical Union journal Geophysical Research Letters.

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.

Storms and Floods

Heavy storm in Free State, South Africa

One killed and 105 others injured in a heavy storm in Sasolburg, Free State region of South Africa. The storm and heavy rainfall damaged more than 1,000 houses.

Tropical Cyclone Dumile strikes Reunion with heavy rains and strong winds.

Britain in 2012 experienced its second wettest year since records began in 1910 and extreme rainfall has become more frequent. Persistent wet weather resulted in total rainfall of 1,330.7mm in 2012, just 6.6mm short of the record set in 2000. Preliminary evidence suggests Britain is getting slightly more rain in total and it may be falling in more intense bursts.

Environment

The southward shift of an atmospheric belt in the Southern Hemisphere since the 1970s is reportedly the reason why parts of Australia and southern Africa are drying out. The southward expansion of a meteorological feature known as the Hadley cell is most pronounced in autumn.

The southward shift of between 125 and 250 miles has resulted in less rainfall during April and May over southeastern Australia, and to a lesser extent over southern Africa.

Rain that previously would fall 125 to 250 miles farther north is now being directed that distance to the south due to climate change’s effect on the Hadley cell.

It is not known specifically what is causing the shift, and climate models have not accurately represented it.

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The week's hottest temperature was 111.2 degrees Fahrenheit (44.0 degrees Celsius) at Nouakchott, Mauritania. This was a record high for the date and for the month of October.

The week's coldest temperature was minus 89.1 degrees Fahrenheit (minus 67.3 degrees Celsius) at Russia's Vostok Antarctic research station.