Heat waves have been noted throughout history, and no doubt occurred well before humans started writing down their histories.
So what's the big deal?
Global warming, to put it succinctly. The proliferation of greenhouse gasses in the atmosphere due primarily to our burning of fossil fuels and the clearing of land for development is trapping the sun's heat near the Earth's surface, leading to more frequent bouts of intense and prolonged heat.
Technically, a heat wave is three consecutive days above 90 degrees. But we all know a heat wave when we feel one.
The deadly 2003 heat wave that baked Europe, killing tens of thousands, was seen by many as a wake up call because its length, extent and impact were unprecedented. The heat wave of the summer of 2007, which engendered countless wildfires across Southern Europe was another.
Some scientists tied the 2003 heat wave, in part, to conditions brought about by global warming, as U.S. federal scientists did with the near-record average temperature across the United States in 2006. And there is greater consensus that the future will bring not only greater average heat, but more heat waves, if global warming continues unabated.
The U.N.'s World Meteorological Organization predicted in 2007 that flooding and heat waves should be expected more and more frequently in the future because of global warming.
Consider this: The temperatures in the Northern Hemisphere in the second half of the 20th Century were very likely higher than any other 50-year period in at least 500 years, and likely the highest in at least 1,300 years. Concurrent with that, extreme weather events have become more frequent in the past 50 years.
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