Possibility of alternating droughts, storms for S.A.
Projections that the San Antonio area will be heating up by almost 2 degrees over the next 30 years means that San Antonians could be looking at a future of alternating periods of drought and heavy rain.
Newly released data from the Associated Press and the National Weather Service show that local temperatures have already increased by an average of just over 1 degree Fahrenheit in the last 30 years compared with the average temperature of the first 60 years of the 20th century.
The study also found that the San Antonio area is continuing to get warmer at a rate of 0.06 degree per year — leading to the projected overall increase of 1.86 degrees in the next 30 years.
If that holds true, the yearly average temperature for the South Central region, which includes San Antonio, would be 71.65 degrees in 2048, as compared with an average yearly temperature of 69.78 degrees over the past 30 years.
The study looked at temperature changes for all of the regions in the United States, of which only the Central Panhandle region of Alaska has experienced a cooling trend since 1988.
But the warming trend is not the only consequence of climate change.
The uptick in heat would also lead to a corresponding increase in periods of drought and heavy rain in Texas, according to John Nielsen-Gammon, the state’s climatologist.
“The combo of more intense rain and higher temperatures means you’ve got longer and more severe dry spells,” he said. “Soil moisture is projected to decrease across Texas also.”
Since 2005, the San Antonio area has seen three major droughts.
Kerry Cook, UT-Austin professor of geological sciences, explained that an increase in the rate that water evaporates might have contributed to past droughts and could lead to future extreme dry periods interspersed with intensely wet periods.
“For every 2 degrees Fahrenheit increase, we’re going to get a 7 percent increase in evaporation,” she said. “That’s measurable in the lab.” With more water being added to the atmosphere, that means more rain coming back to ground. “For global warming, that can translate to a 7 percent intensification of precipitation,” she said.
Cook said she and other climate scientists can model that escalation in certain events, citing Hurricane Harvey as an example.
“We can decrease the carbon dioxide back to pre-industrial values and look at the difference it made in the storm,” she said. “While nobody would say Hurricane Harvey was caused by climate change, it was certainly modified by having increased greenhouse gases in the atmosphere.”
Nevertheless, most scientists are projecting that climate change will mean less precipitation overall, although there’s not a full consensus on that yet, according to Cook and NielsenGammon. But any precipitation changes from global warming will hurt drier areas more than wetter ones, both Cook and Nielsen-Gammon said.
Using renewable energy sources that already exist, along with continuing to develop methods of capturing excess carbon dioxide from the atmosphere can slow down the warming and precipitation trends, Cook said.
But changing the climate, whether it’s warming through carbon dioxide emissions or trying to reverse that change, is an arduous process that takes a long time to see a tangible impact, both scientists emphasized.
“Any changes we make now won’t have much effect over the next couple decades,” NielsenGammon said. “The climate change we see now is the consequence of what’s been happening over the last couple of decades. But just because we can’t reverse the changes (now), doesn’t mean we can’t decrease their magnitude.”