This summer, parts of the USA, Europe, China, and South America have sweltered through extreme heat, sometimes referred to as “heat wave” conditions, although there’s no universal agreement on exactly what a heat wave is and no agreed-upon measure of the severity of extreme heat.
With such imprecision and ambiguity, naturally there is considerable confusion about the impact climate change (a.k.a. global warming) has on extreme heat. Too many people adopt the naive premise that the only effect of climate change is to make each heat wave a couple degrees hotter. The truth of the matter is that because extreme heat is extreme, it is by definition rare, and that is exactly the case in which a small change in the mean value — the result of global warming — can bring about a large change in the number and extremity of extremes. Everyone understands that rare events (like heat waves) are made hotter (on average), but few appreciate how profoundly they are made more common.
This is sometimes illustrated by a graph like this one, of the “probability density” of temperature
Open Mind 