By Robert Burns, Texas A&M University
In this 2010 NASA/Jet Propulsion Laboratory false-color image the immense area of cold water brought to the surface by the La Niña shows as a blue and purple swath stretching from the eastern to the central Pacific Ocean. The 2010 La Niña was characterized as one of the most intense events of the past 50 years, according to climatologists. (NASS/JPL/Bill Patzert image)
There’s good evidence the same factors contributing to the drought – the El Niño-La Niña cycle — have temporarily stalled global warming, according to a Texas A&M University climatologist.
During the last two decades of the 20th century, climatologists recorded a rapid rise in average temperatures. But in the last decade the rise has leveled off, said Dr. John Nielsen-Gammon, Texas State Climatologist, College Station.
"Global temperatures have been relatively flat for the past several years, Nielsen-Gammon said. "Some people use that information to try to imply that global warming has stopped. But it turns out that the factors causing global warming are still there, it’s just that the El Niño-La Niña cycle has temporarily trended cooler and has partially masked the warming."
Nielsen-Gammon compared a strong La Niña’s effect on atmospheric temperatures to that of leaving a refrigerator door open.
"In the tropical Pacific, there’s actually fairly cold water just below the surface," he said. "With a La Niña event, that cold water is drawn all the way up to the surface, and interacts with the atmosphere and causes it to be cooler. If you leave the refrigerator door open, the room will be a little cooler."
But this is a temporary effect rather than a long-term effect, as are the ever- increasing concentrations of greenhouse gases during the last 50 years, he said.
"If my forecast is correct, and there’s no La Niña to hide the underlying warming trend, global surface temperatures are likely to increase and set a new record this year."
For the short term, the next four or five years, farmers and ranchers might hope global warming does pick back up this year, Nielsen-Gammon said.
"On the short term, the same oceanic factors that cause global temperatures to go up temporarily also tends to cause rainfall in the Southern U.S. to go up temporarily," he said.