”And then the dispossessed were drawn west — from Kansas, Oklahoma, Texas, New Mexico; from Nevada and Arkansas, families, tribes, dusted out, tractored out. Car-loads, caravans, homeless and hungry; twenty thousand and fifty thousand and a hundred thousand and two hundred thousand”. – John Steinbeck, The Grapes of Wrath
In 1931 it stopped raining on the great plains of the American West and started blowing clouds of dust. Towns were engulfed, the crops withered and died, and over the next eight years at least 1-billion tons of topsoil was blown away and 2-million desperate people fled in the greatest mass migration of US history.
Arguments over whether the disaster, known as the ”great dust bowl”, was human or natural in origin have raged for decades. But new research suggests that it was caused by minute temperature changes in the Pacific and Atlantic oceans.
Siegfried Schubert of Nasa and colleagues used a computer model to look at the climate over the past 100 years.
The study found that in the 1930s cooler than normal tropical Pacific Ocean surface temperatures combined with warmer tropical Atlantic Ocean temperatures to create a long drought.
This combination, they say in the journal Science, was enough to turn the southern plains, including parts of Colorado, Texas, Kansas, Oklahoma and New Mexico, into a giant dust bowl.
Once the soil had dried out, says Mr chubert, there was less evaporation, which meant even less rain. ”This probably doubled the effect of the drought. It was the major climatic event in the nation’s history,” he said.
”Just beginning to understand what occurred is really critical to understanding future droughts and the links to global climate change issues we’re experiencing today.”
The research may also shed light on how tropical sea surface temperatures can affect weather and climate and how, when rain is scarce and soil dries, there is less evaporation, which leads to even less precipitation, creating a process which reinforces the drought.
But the study is certain to upset ecologists and others who say the disaster was only partly caused by the drought, but largely by ignorance and the intensification of US agriculture. The overstocking of animals and, especially, the continual deep ploughing of the land, which had always been prone to long cycles of drought and rain, they say, exposed the topsoil and led directly to the dust storms.
No one questions the human effects of the disaster, which marked the beginning of the end of the small American farm. Up to 250 000 people fled to California, hoping for a better life but, as the Nobel prizewinner John Steinbeck recorded in his novel The Grapes of Wrath, they were largely disappointed. Agriculture there had already been corporatised and there were few jobs available.
In 1936 a leading agricultural expert persuaded Congress to pay farmers to conserve the soil. By 1938 soil loss had reportedly been reduced by 65%.
The drought ended in September 1939. – Guardian Unlimited Â