Weather Extremes and Climate Change
Scientists cite several statistical indicators that suggest the number of extreme events like heat waves and floods is rising. This evidence has taken on a new meaning in this summer of weather disasters, especially the floods in Pakistan and the heat wave in Russia. The United States has not been spared from weather extremes, notably deluges like the disastrous downpour in Tennessee that led to extensive flooding in May.
For readers who wish to delve more into the science behind extreme weather, the American Geophysical Union has agreed to make public, at our request, a paper from 2009 by Gerald A. Meehl and several colleagues. It is a detailed exposition of the reasons that the number of record high temperatures is now outstripping record lows in the United States, by a ratio of about 2 to 1.
Dr. Meehl, of the National Center for Atmospheric Research, told me in an interview that the “fairly small” average warming in the earth’s temperature, about 1.4 degrees Fahrenheit since the Industrial Revolution, can be expected to lead to “much more noticeable changes in the extremes” of heat and cold.
“Physically, you’d expect to see more record heat events and fewer record cold events,” he said. “That’s what we are seeing.”