It’s a question I get asked a lot.
“What’s the deal with this weather?? It’s been weird!”.
Let’s talk about why. First, a review of the numbers. 2017 has been very warm, with only 3 cooler-than-average months (and 2 of them were barellly cooler).
October is a silly 10+ degrees above average through the first 11 days.
Especially over the last month or so, the weather pattern has gotten “stuck” frequently. The prevailing pattern has featured a big ridge of high pressure over parts of the Midwest and Plains and a trough along or near the West Coast. “Stuck” weather patterns happen. But one wild card this year has been the active tropical season. Hurricanes (and some very strong ones at that) have been tormenting parts of Caribbean and southwest Atlantic. The presence of these systems has, on a few occasions, both amplified the ridge over the US and prevented it from moving away.
“Feedback” loops. Not something you hear about very much in your daily weather report, right? Well, they are important….and probably partly to blame for the recent warm weather.
The basic idea is this: heat can lead to drought and drought can lead to more heat.
Put another way, when the soil and vegetation gets dry, some of the Sun’s energy that would usually be devoted to the process of evaporation (or evapotranspiration) instead gets used to heat the ground (and thus the air).
Put yet another way, when there’s less moisture to evaporate, the Sun can heat the ground and air much more efficiently.
What about the elephant in the room, climate change??
Here’s my 2 or 3 cents. The climate is changing. How much of this is natural and how much is the fault of humans is certainly something that is being studied and debated at the highest levels.
Can individual weather events, or weather trends on the scale of weeks, months, seasons or even a year or two be “blamed” on climate change? That’s tricky business.
I believe the best way to think this is: climate change is not necessarily responsible for every record flood, heat wave, etc but a changing climate INCREASES THE ODDS of extreme weather occurring.
I like this analogy: Remember the “steroid” era of baseball in the late 90s? Mark McGuire and Sammy Sosa (along with many others) hit tons of home runs and it turns out they used steroids to enhance their performance. Every time they hit a home run, was it because they were using steroids? Certainly not. They would have hot many of those pitches out of the yard anyway. But the fact that they were on steroids CHANGED THE ODDS that on any given pitch, they would hit a home run.
The atmosphere is “on steroids” right now.