Climate scientists have been predicting that a warmer Earth will be one in which there are many more extreme weather events, including stronger winds, more frequent torrential rains and floods, and higher temperatures during heat waves.

Take, for instance, those scorching hot days of summer, when it’s impossible to get anything done without the air conditioning on full blast. Not only are these scorchers getting more common, they are affecting a wider geographic area. James Hansen of NASA’s Goddard Institute for Space Studies compared the 30 years from 1951 to 1980, which were used as a reference period, to the most recent decade of 2001 to 2011. In the past, only about one-third of summers had average temperatures that would be considered significantly hotter than typical. However, during the decade from 2001 to 2011, that number had increased to 75% of summers. Meanwhile, the area of the Earth experiencing super-hot summers, with temperatures frequently reaching levels high enough for weather forecasters to warn of a dangerous heat wave, has increased from much less than 1% of Earth’s surface to over 10%, a greater than 10-fold increase.

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One of the most serious societal consequences of a warming Earth comes not from the heat itself, but from changes in the way water moves through our landscapes, farmland, and ecosystems. Scientists expect an increase in the depth and frequency of droughts, interrupted by short bursts of torrential rains and floods. The first decade of the 21st century was marked by a number of such events, and their economic costs are considerable. A 2010 study from the Pew Trust estimated that the global cost of climate change will range from $5 trillion to $90 trillion by 2100 (Figure 14.30).

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Rising temperatures will harm our food system, which will already be stretched thin by a growing human population. According to the Food and Agriculture Organization of the United Nations, global food demand will increase by 70% by the year 2050. Meanwhile, the International Food Policy Research Institute has predicted that climate change will result in less food available per capita across the globe than there was in the year 2000.

We are already seeing the impact of extreme heat events on agriculture today. In 2012 the drought in the United States resulted in low levels of soil moisture during the growing season (Figure 14.31 on page 451). Low soil moisture, in turn, reduced areas of healthy corn and soybean production by one-half and one-third, respectively. Similarly, a 2010 heat wave in Russia decreased grain production by 30%, and a 2011 heat wave in France decreased that nation’s grain harvest by 12%.

Droughts also affect livestock farmers. During the 2012 drought in the United States, over half of rangelands and pastures across the country were in poor to very poor condition, forcing many farmers to sell off cattle. High feed prices led to other farmers selling off hogs. Unless agriculture can adapt to a rapidly changing climate, such shortfalls in production will only worsen.

Extreme heat can be deadly. The summer of 2003 was the hottest one in Europe in the last 500 years. During that heat wave, an estimated 70,000 of people died in 16 countries. The elderly, the infirm, and the poor without adequate air-conditioning systems are typically the victims of such heat events. In 2012 the U.S. Centers for Disease Control and Prevention (CDC) reported that the number of heat-related deaths in the country averaged approximately 700 annually, more than the average total number of deaths in the United States from hurricanes, tornadoes, floods, and earthquakes. With global warming, scientists at the CDC predict that by 2050 annual heat-related deaths will rise to between 3,000 and 5,000.

Climate change is also predicted to increase the prevalence of certain infectious diseases. For instance, insect-borne tropical diseases, such as malaria and dengue fever, will become more prevalent in temperate environments. Dengue fever has recently been reported in the United States in Florida and south Texas, and in European countries, including France and Croatia. Higher temperatures can shorten the length of insect life cycles, resulting in higher densities of disease vectors, such as mosquitoes. High summer temperatures have also been associated with outbreaks of West Nile fever, which were reported from Romania and Greece in 2010 and across the United States and Canada during 2012.

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The torrential rains expected from global warming may also raise the risk of water contamination by a variety of infectious diseases, such as Cryptosporidium and toxin-producing Escherichia coli.