Severe Drought

While climate change has increased precipitation in some areas, in other regions it has contributed to drought.1 Though there are a number of factors that drive drought, such conditions are apt to develop in regions that lack rain; drought is also greatly intensified by increased evaporation from soil and vegetation associated with warming.2 Very dry areas across the globe have doubled in extent since the 1970s.3 In particular, a long-term drying trend (from 1900 to 2008) persists in Africa, East and South Asia, eastern Australia, southern Europe, northern South America, most of Alaska, and western Canada.4

The global increase in drier, hotter areas and the trend in which dry areas are becoming drier can both be traced to the human influence.5 Drying trends have been observed in both the Northern and Southern hemispheres since the 1950s.6 These trends cannot be explained by natural variations but do fit well with climate model expectations for global warming.7 In particular, greenhouse gas emissions have contributed significantly to recent drying by driving warming over land and ocean.8

The increase in drought is caused by many factors: shortfalls in precipitation; earlier snow melt; a shift away from light and moderate rains towards short, heavy precipitation events; and increased evaporation from soil and vegetation due to higher atmospheric temperatures, all of which have been driven at least in part by climate change. Increased heating leads to greater evaporation of moisture from land, thereby increasing the intensity and duration of drought.9

Individual droughts have been linked to climate change, such as the drought that hit central India in 2008 when the north-south pattern of precipitation was disrupted by unusual weather driven by abnormally high sea surface temperatures due in part to global warming