Even though 100 years and 100 ppm CO2 ago it was as hot/hotter.
Andrew Freedman writes at Climate Central:
While each heat wave has ties to short-term weather variability, increasingly common and intense heat waves are one of the most well-understood consequences of manmade global warming, since as global average surface temperatures increase, the probability of extreme heat events increases by a greater amount. Data already suggests that heat waves have are becoming more common worldwide.
One study, published in the Proceedings of the American Academy of Sciences in 2012, found that the odds of extremely hot summers have significantly increased in tandem with global temperatures. Those odds, the study found, were about 1-in-300 during the 1951-1980 timeframe, but that had increased to nearly 1-in-10 by 1981-2010.
Another study to be published in the journal Geophysical Research Letters found that manmade global warming has increased the chances of Australians experiencing extremely hot summers by more than five times, and is likely to raise the odds by even more in the coming decades. Australia experienced its hottest summer on record in 2012-2013, which also featured destructive wildfires and floods.
The heat in the West during the weekend and during the first week in July will also affect inland areas of Southern California and the state’s Central Valley, where excessive heat watches and warnings have been issued for temperatures in the 100s Fahrenheit. The NWS said on Thursday that the strong heat dome may migrate northward through the 4th of July holiday, potentially locking the near-record high temperatures in place for a week or more, raising the risk of wildfires, and bringing a heat wave to places like Salt Lake City, Boise, Portland and Seattle.