The drought which swept across the Midwestern United States in the summer of 2012 has been the most severe and widespread drought of the past 50 years. The population of the Midwest is approximately 61 million people and the region includes the states of Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, Ohio, North and South Dakota and Wisconsin. The percentage area experiencing moderate to exceptional drought in the Midwest peaked at 73.7% in July 2012, according to statistics from the National Oceanic and Atmospheric Administration (NOAA). To date, thousands of acres of farmland have been transformed into cracked earth, livestock have perished, crops have failed and farmers have watched their livelihoods turn to dust. The most recent weekly U.S. Drought Monitor report, which communicates the state of drought in the U.S. on a weekly basis, shows that almost 30% of the Midwest is still experiencing severe drought and over 53% of the area is experiencing moderate intensity drought conditions. This is compared with 6% and 14% respectively one year ago. (U.S. drought Monitor, January, 2013). The Seasonal Drought Outlook released by the National Weather Service earlier this month forecasts that the drought will continue in most dry areas west of the Mississippi River over the next three months, at least. As the drought has wrought havoc across America’s ‘Breadbasket’, namely the corn, wheat and soybean growing states of Iowa, Missouri, Indiana, Illinois, Nebraska, Dakota, fears of a global food crisis have grown due to a shortage in supply and increased food prices for consumers. The summer drought was accompanied by record heat throughout the contiguous United States, with an average temperature of 55.3°F for 2012, that’s 3.2°F hotter than the average for the twentieth century. Overall, 2012 was the hottest year ever recorded in the United States since the NOAA began keeping records in 1895. (NOAA, 2012).
Figure 1. The U.S. Drought Monitor shows drought conditions across the Midwest.
The United States Geological Survey (USGS) describes a drought as an ongoing period of drier than normal conditions that results in water-related problems. This can happen when a region receives less rain or snowfall than normal, or when there is an increase in evaporation from the soil. Increased soil evaporation or evapotranspiration is usually a result of warmer temperatures. Often it can be a combination of factors that cause a drought and therefore scientists generally agree that it’s extremely difficult to determine if a single event can be attributed to global warming, to the exclusion of all other natural weather variables.
The answer to the question of whether global warming caused the drought in the Midwest depends on who you ask, really. Some climate change scientists may say “yes” but climate sceptics could be expected to respond with a resounding “no”. A strong argument in the sceptics’ favour is that America has suffered worse droughts in the past. The worst droughts in modern times in the United States occurred in the 1930s and the 1950s. The Dust Bowl of the 1930s affected the Oklahoma and Texas panhandles but also spread into parts of New Mexico, Kansas and Colorado. The later drought of the 1950s began in Texas and New Mexico but became more widespread towards the middle of the decade. Aside from these modern day extremes, scientists have also revealed through the research of tree-ring data that North America suffered “megadroughts” which lasted for periods of between 20 and 40 years during the medieval period, between the 11th and 14th centuries AD. They have been able to examine the frequency, severity, distribution and persistence of droughts over a 1,000 year period through the use of gridded reconstructions developed from tree-ring data and are able to tell that, although the megadroughts lasted much longer than any drought...