​​Human influence

Peter Stott, who leads the climate monitoring team for the Met Office Hadley Centre, a climate research institution in southwest Britain, says La Nina is only part of the story. He co-authored the American Meteorological Society study which links climate change with the Texas drought and other extreme weather events.

“We did find clear evidence for human influence on the Texas heat wave and also in the very unusual temperatures we had in the United Kingdom in 2011,” he says.

The study finds the 2011 Texas drought was 20 times more likely to occur than in the 1960s as a result of human-induced climate changing emissions in the atmosphere. The heat wave last November in England was 62 times more likely to have occurred than 50 years ago, according to the report.

While not all extreme weather events can be linked to climate change, Stott and his colleagues found evidence that they are more probable in a warmer world.

“What we must remember is that it is the combination of natural variations of climate that is important here," Stott says. "We saw that in La Nina in Texas, but, over and above that, there is this additional climate effect that can and has indeed in the last year led to a greater vulnerability to extreme weather.”

Worsening conditions

Drought continues to parch other parts of the U.S., sparking wildfires and damaging crops in one third of the nation’s counties. U.S. scientists predict that these conditions could even get worse in the coming months, which doesn’t bode well for Iowa farmer Tom Zaputil’s corn crop, which hasn’t had a significant rain since June.