Drought

Studies of tree rings in the United States have identified droughts occurring as early as 1220. The thickness of annual growth rings of some tree species, such as red cedar and yellow pine, indicates the wetness of each season. The longest drought identified by this method began in 1276 and lasted 38 years. The tree ring method identified 21 droughts lasting five or more years during the period from 1210 to 1958. The earliest drought recorded and observed in the United States was in 1621. The most well-known American drought was the Dust Bowl on the Great Plains from 1931 to 1936. The years 1934 and 1936 were the two driest years in the recorded history of U.S. climate. The Dust Bowl encompassed an area approximately 399 mi (644 km) long and 298 mi (483 km wide) in parts of Colorado, New Mexico, Kansas, Texas, and Oklahoma. More recently, the United States experienced severe to extreme drought in over half of the country during 1987–89. This drought was the subject of national headlines when it resulted in the extensive fires in Yellowstone National Park in 1988.

Droughts have also had enormous impact in other regions of the world. A drought in northern China in 1876 dried up crops in an extensive region. Millions of people died from lack of food. Russia experienced severe droughts in 1890 and 1921. The 1921 drought in the Volga River basin caused the deaths of up to five million people—more than had died during World War I, which had just ended. India normally receives most of its rain during the monsoon season, which lasts from June to September. Winds blowing in from the Indian Ocean bring most of the country's rainfall during this season. The monsoon winds did not come during two droughts in 1769 and 1865. An estimated 10 million people died in each of those droughts, many from diseases like smallpox, which was extremely contagious and deadly because people were already weakened from lack of food. More recent severe droughts occurred in England (1921, 1933–34, and 1976), Central Australia (1945–72), and the Canadian prairies (1983–5).

Almost the entire continent of Africa suffered from droughts in the last quarter of the twentieth century. Ethiopia, usually considered the breadbasket of eastern Africa, was hit by a brutal drought in the early 1980's. A dry year in 1981 resulted in low crop yields. Three years later, another dry year led to the deaths of nearly a million people. Drought conditions again threatened eastern Africa in 2002. An estimated 15 million people in Ethiopia, three million in Kenya, 1.5 million in Eritrea and three million in Sudan could face starvation as a result of drought. According to the World Health Organization, drought is the cause of death for about half the people who are killed by natural disasters.

Between 1968 and 1973, Sahel (a region in east Burkina, a country in western Africa) suffered a great drought. An estimated 50,000–200,000 people died as a result. While the causes of these great African droughts are unknown, research is beginning to indicate that droughts could result from a combination of global and local climate patterns. Satellite imagery links El Niño and vertical ocean mixing patterns to dry weather in Sahel. In addition, desertification may be a positive feedback mechanism driving the climate towards drought conditions. In regions where there are few surface water reservoirs such as Sahel, the major source of precipitation is transpiration from plants. As plants become sparse in drought conditions, this source of water for precipitation is diminished. The diminished precipitation further decreases the growth of vegetation.

Since 1994, drought and famine in North Korea have been worsened by the political situation. The government of North Korea has allowed its people to starve rather than continue talks with South Korea and famine relief organizations. Over 50% of the children in North Korea are suffering from malnutrition and lack of water, and countless numbers have perished. The drought may accelerate political problems in the region if starving refugees from North Korea flee to China and South Korea.