NASA Study Links Extreme Summer Heat to Climate Change
HARI SREENIVASAN: So, explain the — how we know that these events are happening and that they are not part of any sort of natural cycle?
JAMES HANSEN: They are, in fact, a product of global warming, and we can see that very easily.
One thing, I think that the public can appreciate, what we call the bell curve. You know when you have a random variable, they tend to fall on both sides of the average value, sometimes colder than normal, sometimes hotter than normal.
And this is the way this bell curve looked in the 1980s. But, as time went on, as the planet gets warmer, it starts shifting toward the right, and you get more red and less blue.
And, by now, this past decade, it has shifted so far that we have got about 10 percent of the cases out here in this extreme warm anomaly, more than three standard deviations.
And, to understand, averaged over the whole summer, it is only a few degrees warmer, a few degrees Celsius warmer. But that is a big effect. To see how important that is, look at Moscow two years ago, Texas last year, the Midwest this year.