Heatwaves are increasingly common and increasingly intense and long lasting in the U.S. June was hot in the U.S. and so was July. The month of July started with a heatwave that enveloped almost half the country and just past the middle of the same month another heatwave saw even hotter temperatures.
While the June heatwave saw temperatures exceed 90 Fahrenheit (32° Celsius) in one third of the country, the second July heatwave saw more than half of the country enduring temperatures surpassing 100° F (38° C) when the humidity was factored.
On Saturday, July 20th new one-day temperature records were recorded in more than a half a dozen places including New York and Michigan. In this heatwave two-thirds of the Lower 48 states stifled under some of the hottest hottest weather in the U.S. since 2012.
These heatwaves are being compounded by high humidity which make it feel even hotter. In some places the combination of heat and humidity pushed heat indexes as high as 115° F (46° C). This heatwave was also notable for its warm overnight temperatures which NOAA data indicates has increased at twice the rate of summer days.
On the periphery of these heat domes is an area being described by meteorologists as the ring of fire. This is a zone where severe storms can develop. The heatwave and related storms caused power outages in areas ranging from Michigan to New York.
A slew of studies indicate these heatwaves are more likely due to global warming. The cause of the recent heatwaves in the U.S. and elsewhere is the jet-stream. A
warmer world has caused the jet-stream to meander and slow down. According to a 2016 study in Nature Scientific Reports,
led by climatologist Michael Mann, record temperature years are 600 to
130,000 times more likely thanks to anthropogenic climate change. Studies also show they are also longer and more intense. Some of the most dire predictions indicate that by the end
of the century the combination of of heat and humidity could push the
heat index past a potentially fatal 131° F (55° C).
They will only get worse if we fail to do what common sense dictates. We must significantly reduce our greenhouse gases if we are to keep temperatures from increasing above the upper threshold limit. According to a recently published study, if we do not succeed in reigning in our greenhouse gases, parts of Florida and Texas could see temperatures over 100 F (38° C) for almost half the year.
A U.S. National Climate Assessment (NCA) report states that under a high emissions scenario temperatures in the country will increase by 9° F in the last quarter of this century. The NCA report also states that temperature extremes are rising at an even faster rate than average temperatures. In a couple of decades five day heat waves could be 12° F warmer.