The University of Arizona

Thoughts on the Texas Fires

April 27, 2011
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Flying over Texas last weekend, I saw clouds of smoke at 30,000 feet. Texas is burning, with many fires, fueled by strong winds, destroying forests, houses, churches, and ranches all over the state. (Check out this map from the Texas Forest Service). As of April 27, 17 large fires were torching 573,500 acres, according to the Texas Forest Serivce. In a sign of desperation, Gov. Rick Perry proclaimed Friday, April 22, to Sunday, April 25 as days of prayer for rain in the state of Texas.

However, we don’t have to invoke the supernatural to understand why these fires are ravaging the Lone Star State. It’s a combination of long-term climate changes and short-term weather. Let’s start with the long-term changes: Texas is in a major drought.  According to the most recent U.S. Drought Monitor map from April 19, most of Texas is experiencing extreme to exceptional drought. March 2011 was also the driest March in recorded history for Texas (see map of rankings and time series of precipitation). The cause of this drought is partly due to a strong La Niña in the tropical Pacific during the last year. In the southwestern U.S., including Texas, La Niñas cause warm, dry conditions, whereas El Niño events lead to wetter conditions.

La Niña conditions are also associated with more hurricanes and tropical storms in the Atlantic; the La Niña of 2010 followed suit. And, according to the Texas state climatologist John Nielsen-Gammon, a wet summer in Texas last year, partly due to increased moisture from landfalling Hurricane Alex, caused abundant vegetation growth. This extra vegetation, rendered into tinder by the deadly cold snaps of last winter and the subsequent drought, set up prime conditions for wildfire.

Then there are the short-term changes that sparked the blazes: strong winds (typical in spring) hotter temperatures, no precipitation, and of course, humans setting fire to things (intentionally and unintentionally)--unsafe burning of debris is number one cause of Texas wildfires, according to the TX Forest Service.

Unfortunately for the subtropical latitudes, where Texas sits, the long-term future doesn’t look too good.  Although we don’t know how El Niño and La Niña frequency and intensity will change in the future, it is clear that pumping more greenhouse gases into the atmosphere will likely expand the Hadley Cell, pushing the dry zone usually centered around 30°N and 30°S further poleward. This means dry times for the southwestern U.S., including Texas. Let’s pray that policymakers understand the consequences of increasing CO2 for Texas and the rest of the Southwest, and work towards reducing our greenhouse gas emissions.