Today marked the seventh day of a major heat wave, the second of the summer across southern New England. The unrelenting heat and humidity have taken their toll on our collective mood as this is not normal summer weather in our part of the country.
The past three weeks have seen the warmest 21 days ever recorded in 151 years of records in Boston, similar to temperatures in Missouri or North Carolina where this type of heat and humidity is expected. Coupled with growing drought, damage to plants has spread from wilting flower boxes to struggling trees and shrubs. Drought is actually not increasing in New England but in a warmer climate, the impact of even semi-regular droughts can be greater when accompanied by hotter air.
These types of hot and dry weather events are ripe for all sorts of hyperbole. On one end of the spectrum, you’ll find people who say we’ve had similar weather before and this summer is just more of the same. On the end of the scale you’ll hear people call the past three weeks climate change itself. Neither is an accurate way to relate hot weather to the long-term climate. More correctly, our recent weather has been extreme and climate change is likely playing a role.
After tomorrow the heat will break and eventually the humidity will as well. I expect we’ll also have numerous showers although the drought could linger well into the fall.
When summer is over, we will have another opportunity to fully analyze the statistics, but already a few things are true. In addition to the extreme temperatures, we are experiencing the longest stretch of 80 degree or above weather on record —Tuesday will be the 26th day in a row of temperatures that are 80 degrees or higher.
What is also true is that the changing climate means these types of hot weather events become more likely to occur, and when they do, the upper limits of temperature, along with the length of time the heat lasts, are increasing. Warm records far outpace cooler ones and the gap is growing. This is clear from the two graphs below.
I see people point out how there are still older, warmer records in the books. This is a flawed way of looking at our unambiguous warming trend. As an example, no one would say that life expectancy hasn’t increased over the past 25 years just because Jean Calment’s record of living to 122 hasn’t been broken yet.
With the current accelerating warming, all the high-temperature records across the globe will likely be broken in the coming decades as well Calment’s. Outliers are interesting and make for good headlines, but they don’t tell us anything about a trend as long as they’re outliers.
The heat will abate later this week, but these past three weeks of unprecedented warmth should be a wakeup call to what lies ahead. The number of hot days will continue to go up, and everything that goes along with this type of heat will continue to be amplified.