Extreme weather

Extreme weather includes unexpectable, unusual, unpredictable severe or unseasonal weather; weather at the extremes of the historical distribution—the range that has been seen in the past. Often, extreme events are based on a location’s recorded weather history and defined as lying in the most unusual ten percent. In recent years some extreme weather events have been attributed to human-induced global warming, with studies indicating an increasing threat from extreme weather in the future.

According to IPCC (2011) estimates of annual losses have ranged since 1980 from a few billion to above US$200 billion (in 2010 dollars), with the highest value for 2005 (the year of Hurricane Katrina) . The global weather-related disaster losses because many impacts, such as loss of human lives, cultural heritage, and ecosystem services, are difficult to value and monetize, and thus they are poorly reflected in estimates of losses.

Heat waves are periods of abnormally high temperatures and heat index. Definitions of a heatwave vary because of the variation of temperatures in different geographic locations. Excessive heat is often accompanied by high levels of humidity, but can also be catastrophically dry.

Because heatwaves are not visible as other forms of severe weather are, like hurricanes, tornadoes, and thunderstorms, they are one of the less known forms of extreme weather. Severe heat weather can damage populations and crops due to potential dehydration or hyperthermia, heat cramps, heat expansion and heat stroke. Dried soils are more susceptible to erosion, decreasing lands available for agriculture. Outbreaks of wildfires can increase in frequency as dry vegetation has increased likeliness of igniting. The evaporation of bodies of water can be devastating to marine populations, decreasing the size of the habitats available as well as the amount of nutrition present within the waters. Livestock and other animal populations may decline as well.

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