[Texgreen] Texas could lose 40% of crops to global warming

[Roger Baker]

<http://www.chron.com/disp/story.mpl/front/4523120.html>


<http://www.chron.com/disp/story.mpl/front/4523120.html>

Severe heat, drought predicted for 22nd-century Texas

By ERIC BERGER

Copyright 2007 Houston Chronicle


... Paradoxical prediction

It shouldn't take more than a few degrees to disrupt Texas - bringing  
more heat waves, flooding and, paradoxically, drought, local  
scientists say.

"Texas will face a number of challenges, but the most serious is  
probably a shortage of water," said Gerald North, distinguished  
professor of climate at Texas A&M University.

Water evaporates quicker at higher temperatures. Although North said  
model results vary, Texas generally is expected to get a bit less  
rainfall. To offset the increased evaporation in a warmer Texas, the  
state would need 25 percent to 40 percent more rain, he said.

The result could be desertification of the western half of Texas.  
Currently, Austin gets about 2.6 inches of rain per month.
If temperatures climb 5 degrees, and there's no additional rainfall,  
evaporation effectively would cut the monthly total to 1.6 inches,  
North said.

Rivers may run dry

Rivers - such as the Brazos, Colorado and Rio Grande - that are  
sustained by runoff probably would dry up before reaching the Texas  
coast, he added.

Eric Barron, dean of the Jackson School of Geosciences at The  
University of Texas at Austin, agreed that water will be a central  
concern, and that warming almost certainly will exacerbate the problem.

"We are changing the composition of the atmosphere in a way that will  
promote warming, in a way that will have consequences," Barron said.

"I don't think you can argue about that any more. You just can't."

Fewer water resources would harm Texas' farming industry, said Bruce  
McCarl, a professor of agricultural economics at A&M. Based upon the  
IPCC global warming scenarios, he said, Texas could lose 40 percent  
of its crop acreage.

In warmer weather, crops require more water, and a drier Texas bodes  
poorly for universal access to irrigation, upon which much of the  
state is dependent. Corn, rice and grazing livestock would be  
vulnerable, he said, but some crops, such as tomatoes, citrus fruit  
and cotton, could benefit from the heat.

Many models suggest an even slightly warmer world will significantly  
increase the number of heat waves, which often come when high- 
pressure systems dominate the atmosphere. Under such conditions  
temperatures rise and winds fall.

These changes won't come immediately, the scientists say. Climate  
change generally is a gradual process rather than one of singular  
catastrophes. Humans are slowly, and perhaps somewhat irreversibly  
changing their world, they contend, and not for the better.

"If you're worried about the weather over the next five to 10 years,  
nothing alarming should happen," Nielsen-Gammon said. "But if you  
care about the globe 100 years from now, there are lots of reasons to  
be alarmed."