Think the punch of 90-degree-plus heat expected later this week is hot? Soon we could be wishing for that kind of balmy weather. According to a new study by Stanford University scientists, by the middle of this century "even the coolest summers will be hotter than the hottest summers of the past 50 years."
That's the word from lead author Noah Diffenbaugh, whose team will publish the study this month in the journal Climatic Change Letters. The scientists, who were funded by the Department of Energy, the World Bank and others, drew upon more than 50 climate model experiments and historical weather data to forecast the effect of unmitigated greenhouse-gas emissions on seasonal warming. All signs, they say, point to a significant bump in summer temperatures as soon as 20 years from now. Oh, and that bump will be "permanent."
The tropics are likely to warm up first, but by 2070 folks in North American, China and Europe could all be sweating profusely. What's particularly worrisome about this new data is that the scientists intentionally used non-alarmist projections of future greenhouse-gas emissions, and still came up with a startling increase in worldwide heat. Says Diffenbaugh:
The fact that we're already seeing these changes in historical weather observations, and that they match climate model simulations so closely, increases our confidence that our projections of permanent escalations in seasonal temperatures within the next few decades are well founded.
Hotter summers don't just mean higher energy bills and uncomfortable clothes. The impact to agricultural production is expected to be severe - the Midwest's corn and soybean harvest could be cut by as much as 30 percent - and humans famously don't deal well with extreme heat. As an example, Diffenbaugh cites the 2003 heat wave in Europe that killed 40,000.