The Return of the Dustbowl

When it comes to the environment, the bad news seems to never end. In the course of the most arid years, each acre of farmland can lose up to 70 tons of soil and then, wherever the dust is dumped, it can smother the crops it lands on. In the Oklahoma Panhandle, the most remote area of the state, recent rainfall has been so meagre that fears have been kindled of a return to the apocalyptic "Dust Bowl" scenes of the 1930s. Back then, agriculture collapsed and thousands of people left.

Gary McManus, the Oklahoma State Climatologist, told the BBC: "The drought right now is the worst in decades especially in western Oklahoma. This has had a big economic impact on our economy - if you look at agriculture in 2011-12 alone there were $2bn losses from crops and cattle." He highlights rainfall statistics for the weather station in Boise City in the midst of one of the hardest-hit areas, Cimarron County, where the total from October 1 2010 to June 12 2014 was just 43 inches. By comparison, over the same period in the 1930s, a time of extraordinary hardship, Boise City received only 41.62 inches of rain.

Dr Renee McPherson of the University of Oklahoma, author of the Great Plains chapter of the recent National Climate Assessment says the region experiences very large climate variability but that models suggest there will be a rise in maximum temperatures this century. That could increase evaporation from the ground and transpiration from plants.

"We're less sure of what will happen to our precipitation patterns, but even if they stay the same, we'll see increased drying with those increased temperatures," she explained. "We aren't sure what the droughts will look like in future - whether they'll be longer - but we feel that because of the increasing temperature they will be intensified."

US scientists have modelled how a 1930s-like "dustbowl" drought might impact American agriculture today, and found it to be just as damaging. A repeat of 1930s weather today would lead to a 40% loss in maize production. In a 2-degree warmer world, it becomes a 65% reduction, the team projects.

"And what we see at higher temperatures is that these crops - maize and also soy - are so sensitive that an average year come mid-century could be as bad as 1936, even with normal precipitation," explained Joshua Elliott, from the University of Chicago's Computation Institute.

Looking at the production of the major grains - rice, wheat, maize and soybeans - the taskforce's scientists found that the chances of a one-in-100-year production disruption was likely to increase to a one-in-30-year event by 2040.  One factor that does not help is the way that production of some of these important crops is highly concentrated. The US, for example, is the leading producer in the world for maize, with most of it grown in just Iowa, Minnesota, Nebraska, and Illinois. But Dr Elliott said this concentration would have to be broken up, that a different and more varied approach would be needed if more extreme weather became the norm in the decades ahead. Maize might be better grown further north than the traditional Midwest states, he suggested. "It's most likely they will have to start growing other crops. "Maybe by mid to late century, Iowa will be known as the cotton state rather than the corn state, because cotton will basically have been eradicated out of much of the southern states because the temperature thresholds will have blown way past what cotton can handle there.

Tim Benton from the UK's Global Food Security Programme said  "Rather than seeing bad years as something that's rare and unlikely, we should go into each season with an expectation that 'average weather' doesn't exist anymore. It's either too hot, or too wet, or too cold or too dry. An average summer is very difficult to find these days."