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Texas Scientists: $5 Billion Drought Caused By Deadly Combination Of Climate Variability And Carbon Pollution

By Brad Johnson  

"Texas Scientists: $5 Billion Drought Caused By Deadly Combination Of Climate Variability And Carbon Pollution"

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Texas is reeling from its most severe and expensive drought in history, tipped to extremes by greenhouse pollution, the state’s climate scientists say. The $5.2 billion in losses estimated by the Texas Agrilife Extension Service already exceeds the previous record of $4.1 billion during the 2006 drought, and the drought is expected to continue for months. Furthermore, the “loss estimates do not include losses to fruit and vegetable producers, horticultural and nursery crops, or other grain and row crops.”

In a video presentation, Texas A&M University soil scientist Travis Miller, a member of Gov. Rick Perry’s (R-TX) Drought Preparedness Council, explained that the strong La Niña during the fall and winter is tied to drought in the southern U.S., and rejected a role for climate change, despite the record-shattering heat:

There’s a lot of speculation why we’re having this weather pattern we’re having. Some people attribute it to climate change. But in essence, if you go back and study weather records, We have 116 years of weather records in Texas. It’s been this variable all the way back to 1895 when we first started records. What we’re experiencing is climate variability instead of climate change. Over that 116 years we have seen a tiny trend towards less moisture. Maybe .11 inches per decade if you average all the peaks and valleys in rainfall.

Watch it:

Dr. Miller, although an expert on soils and agriculture, needs to talk more to the climate scientists in the state, including his colleagues at Texas A&M and on the Drought Preparedness Council.

“There’s no question that natural climate variability has a huge impact on Texas,” Dr. Kathanie Hayhoe, a climate scientists at Texas Tech University, told ThinkProgress Green, referring to the impacts of El Niño and La Niña conditions on the state. However, climate change cannot be ignored, she said:

Trying to pin any one event or season on either natural variability or climate change is a false dichotomy. It’s like trying to pin our health problems on either poor diet OR lack of exercise, but not both. Clearly, there can be multiple factors affecting our health at the same time. In the same way, there can be multiple factors affecting our climate at the same time.

This combination of natural cycles of climate variability on top of altered background conditions of climate change could be a one-two punch for locations that are already vulnerable to natural climate extremes. Identifying and studying those areas, in order to identify ways that we can increase our resilience in the face of an uncertain future, should be an important research priority.

Dr. Miller’s colleague at Texas A&M, climate scientist Andrew Dessler, emphasized the point that man-made climate change is “almost certainly” making the drought worse. He told ThinkProgress Green that “there is absolutely no way you can conclude that climate change is not playing a role here”:

While La Niña may be playing an important role, we also know that humans have warmed the climate, and that is almost certainly making this extreme event worse. Given that this last July was the warmest month in the entire observational record for Texas, and with the driest 12 month period that ends in July on record, there is absolutely no way you can conclude that climate change is not playing a role here. I’m quite surprised that anyone would even suggest that.

Dr. John Neilsen-Gammon, the Texas State Climatologist and the only climate scientist on the Texas Drought Preparedness Council, agreed that man-made warming is worsening the natural variability at work in the record drought. He explained to ThinkProgress Green that the “primary known influences” on the drought are oceanic patterns like La Niña and the Pacific Decadal Oscillation, which “have little to do with climate change.” However, because of global warming, “evaporation has been enhanced, soils and plants dried out faster, streamflow declined faster, and temperature records were easier to break.”

2011 marks the fifth billion-dollar drought for Texas since 1998. Although this year’s drought has “no end in sight” unless hurricanes come through, the real trouble for Texas looms in the future, as greenhouse concentrations from fossil fuel combustion continue to rise. “Looking forward, if global temperatures continue to rise but Texas precipitation stays the same,” Nielsen-Gammon warns, “Texas droughts would nonetheless become more severe because of the warmer temperatures.”

The Texas Drought Project is working to prepare the state for the coming perpetual drought it is now likely to face because of the burning of the world’s fossil fuels, much of which came from below the now-parched ground of Texas.

John Nielsen-Gammon’s e-mail to ThinkProgress Green, in full:

The IPCC models have Texas precipitation decreasing by about 5% over the current half-century, but our analysis shows that Texas precipitation increased by about 10% over the 20th century. These are conflicting signals, so we really don’t know whether Texas precipitation will increase or decrease in the future.

Drought in Texas is tied closely to La Nina, which tends to produce dry winters. This year’s drought fit the mold; it was triggered by the moderate to strong La Nina of 2010-2011. More work needs to be done, but it appears from my preliminary analysis that La Nina’s effects on the jet stream over North America continued unusually long into the spring. May and June are normally among the wettest months of the year in Texas, and they were unusually dry.

In the summertime, drought and heat go hand in hand. Dry ground means little evaporation and thus little fuel for thunderstorms. Meanwhile the energy from the Sun that would have produced evaporation instead produces heat. So dry summers in Texas are also hot summers.

On a multi-decade scale, Texas precipitation is strongly affected by the Pacific Decadal Oscillation, or PDO. When the PDO is negative, as it has been since 2000 or so, Texas is especially susceptible to droughts. That susceptibility is likely to continue for another five to fifteen years, depending on how long the present phase of the PDO lasts. Atlantic sea surface temperature patterns also affect central US droughts.

So the primary known influences on Texas annual precipitation have little to do with climate change. We don’t even know whether La Nina will become more or less frequent or intense in the future; the scientific evidence is mixed.

The main known effect of global warming so far on the drought has been through temperatures. With temperatures both globally and in Texas running 1-2 F warmer in the past decade than they were several decades ago, it’s reasonable to say that global warming has made this drought 1-2 F hotter than it would have been otherwise. This means that evaporation has been enhanced, soils and plants dried out faster, streamflow declined faster, and temperature records were easier to break.

Looking forward, if global temperatures continue to rise but Texas precipitation stays the same, Texas droughts would nonetheless become more severe because of the warmer temperatures.

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