Part of this article is about weather and part of it is about climate.
“Climate is what you expect; weather is what you get” is an old saying in my field, and it’s about right. But this summer makes the distinction fuzzier. Globally, the Associated Press tallied many nations’ weather and emergency agencies and reported more than $50 billion in damage and more than 2000 deaths from flooding and heat. Droughts parched many parts of the United States, Canada and India, and the wildfires that accompany droughts reached new heights of frequency and coverage.
In the United States, National Weather Service Director Dr. Louis Uccellini noted, “We’ve experienced an increasing number and a disturbing number of weather extremes this summer.”
Flooding made the news more often than any other weather extremes in the United States this summer. But something else was going on, and that’s where the boundary between weather and climate really became less distinct.
Nighttime heat was the culprit most unnoticed in the news, except where it was causing increased suffering and mortality. It was literally extraordinary in some places. Deke Arndt, chief of the National Oceanic and Atmospheric Administration's Climate Monitoring Branch, points out that 72 degrees is a critical recharging temperature overnight for plants and humans, and it can be a point at which the air conditioning gets turned off. That didn’t happen enough in all too many places this summer.
For example, in Tallahassee, nighttime lows stayed above 72 degrees for 74 consecutive days. Not even in Florida are residents acclimated to that kind of extreme record stretch of discomfort. In New Orleans, the numbers are even more startling. That steamy city had 43 – count 'em – 43 nights when the temperature didn’t drop below 80.
Just imagine that.
If you doubt that’s extraordinary, you’re wrong. The previous record set in 2010 was 13. Western New Yorkers cannot begin to fathom that kind of awful discomfort. We have NEVER had a single day with a minimum of 80 or higher in our record-keeping history, which goes back to 1871.
This extra heat in the air increased evaporation and put much more water vapor in the atmosphere over the Gulf of Mexico. The extremely high volume of precipitable water contributed to the devastating floods that hit Louisiana.
While these events and disasters can be taken as weather extremes, they are also markers for a warming climate. Dr. James Hanson, retired head of NASA’s Goddard Institute for Space Studies, became a target for warming denialists because he (unwisely or unwisely) became an advocate for legislation and treaties to fight warming.
However, in 1988 he predicted there would be large increases of nights with low temperatures above 75 degrees and large increases of daytime high temperatures exceeding 95 degrees much more often in at least four U.S. cities by the 2010s. In fact, his forecasts from climate models in that era have actually underestimated how hot it would get in six out of eight categories, according to Gavin Schmidt, NASA Chief Climate Scientist.
In other words, despite Hanson’s having become politically engaged, much of his science stands as confirmed, conservative and essentially correct.
It is theoretically possible that lingering impacts from El Niño contributed a bit to the extreme heat in the early part of the summer, but El Niño was gone by mid-May. El Niño was not the driving force behind the extreme events of this summer, if at all.
One very troubling impact from such extreme nighttime temperatures is the established link with premature mortality, especially in the elderly, those with chronic cardiovascular problems, asthma and other respiratory problems, and infants.
When a record jumps from 13 80-plus degree nights in New Orleans in 2010 to 43 80-plus degree nights just six years later, that is unquestionably cause for concern about where we are headed.