April 12, 2013
Climate Change Not At Fault For Record US Drought In 2012
Brett Smith for redOrbit.com - Your Universe Online
In pushing for his green agenda, President Barack Obama has repeatedly cited last year´s massive drought, which cost the US $35 billion, as evidence of climate change.
However, a new report from the National Oceanic and Atmospheric Administration (NOAA) found that a bizarre confluence of natural variations was responsible for the precipitous drop in rainfall levels across the United States last summer.
"This is one of those events that comes along once every couple hundreds of years," lead author Martin Hoerling told the Associated Press. "Climate change was not a significant part, if any, of the event."
Last year, moist air from the Gulf of Mexico did not flow as it normally does — northward. According to the report, the Jet Stream that customarily brings moisture from the Gulf and into the contiguous US was trapped up north in Canada. As a result, July and August saw markedly less rainfall than previous years.
While some researchers have linked changes in Jet Stream behavior to shrinking Arctic sea ice — Hoerling said those connections are not valid in this instance.
Along with scientists from five different governmental agencies, Hoerling created a series of computer simulations, factoring in climate change conditions. Based in these simulations, the scientists found climate change was not a factor in the drought.
Hoerling told the AP that he performed a similar analysis on the 2011 drought in Texas. That analysis discovered that climate change was indeed a factor. Hoerling also noted that climate change factors were influential in previous droughts near the Mediterranean Sea.
According to the scientist, over the past 20 years there has been a greater frequency of La Ninas, or widespread cooling of the central Pacific Ocean. Hoerling said that cyclical factor, which is not attributed to global warming, increases the chances of droughts occurring.
The report, which focused primarily on Wyoming, Kansas, Nebraska, Colorado, Missouri and Iowa, was immediately refuted by several climatologists.
Kevin Trenberth, climate scientist at the federally-funded National Center for Atmospheric Research (NCAR), told the AP that the report didn't consider the lack of snowfall in the Rockies over the winter and how this could have affected overall moisture in the air. He added that the study ignored how global warming strengthened the high pressure system, keeping the Jet Stream north and the rainfall away from the plains.
"This was natural variability exacerbated by global warming," Trenberth said. "That is true of all such events from the Russian heat wave of 2010, to the drought and heat waves in Australia."
The precipitation deficits from May to August of 2012 were the most brutal since official measurements began in 1895, even drier than summers of 1934 and 1936, which occurred during the height of the Dust Bowl.
In combination with above normal temperatures, the lack of rainfall resulted in the largest drought-affected area of the contiguous United States since the inaugural year of the US Drought Monitor in January 2000, reported Doyle Rice of USA Today.
Generated in the federal government, the Drought Monitor is a weekly report on drought conditions around the country. According to the report, moderate to extreme levels of drought hit 61 percent of the lower 48 states.