On this edition of Climate Cast, Paul Huttner talks with Jennifer Francis, a climate scientist with the Woodwell Climate Research Center, about drought and it’s connection to climate change. Can you say jet stream?
Dry conditions in 2020 set up a scenario for a major drought in Minnesota during 2021, as persistent moisture deficits combined with above-normal temperatures across the state. Some areas saw the most severe drought situations in 40 years. By mid-August, 8% of the state was designated in Exceptional Drought, and an additional 42% of the state was in Extreme Drought.
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[MUSIC PLAYING] SPEAKER 1: More than half of the state is now experiencing severe drought.
SPEAKER 2: Mississippi River levels near record lows.
SPEAKER 3: We are way below where we should be.
PAUL HUTTNER: The weather numbers clearly show Minnesota is getting warmer and wetter overall. So why is drought the weather story of 2021 in the upper Midwest? The simple answer, climate change accelerates the pace of extreme weather swings. Now let's dig deeper. Climate scientist Jennifer Francis studies how climate change impacts jet stream patterns at the Woodwell Climate Research Center in Massachusetts. Hi, Jennifer. Welcome back to Climate Cast.
JENNIFER FRANCIS: Hi, Paul. Thank you so much for having me.
PAUL HUTTNER: So I'm sitting here in Minnesota today. We're in really a flash drought that has developed quickly this year. We've just had the worst wildfire smoke event on record in Minnesota. So this is where my job of explaining the link between extreme weather swings and climate change is a challenge. What's your elevator speech on the link between climate change and these extreme swings we're seeing this year around the globe?
JENNIFER FRANCIS: All the weather that we experience is completely controlled by what the jet stream is doing. And when the jet stream is north of you in Minnesota, then you're in the warm air on the south side of the jet stream.
And when it dips South of you, then you're in cooler air. But then it also depends on whether you're in one part of a jet stream wave or another part. So when you're in the winds that come from the northwest, they tend to be very dry, you tend to have nice weather, blue skies, and that can lead to drought if it lasts a long time.
And the opposite is true when the winds are coming from the southwest, so bringing lots of tropical moisture up your way. If that pattern lasts for a while, it can lead to flooding like we're seeing in parts of the southern Midwest and parts of the Mississippi Valley.
PAUL HUTTNER: Talk a little about the configuration and the speed of the jet stream. We've seen this drought develop rapidly this year. How does a lazy or stuck jet stream make these extremes develop more quickly?
JENNIFER FRANCIS: Right. So the Western states, generally speaking, have been under one of these big northward swings in the jet stream, and that prevents all the storms really from getting into the west and alleviating the long term drought that they've been suffering there.
And then once you get one started and you dry out that soil, it just makes it that much harder to recover from a heat wave because the dry, hot soils really feed into that dome of hot air that sits in one place and makes it even stronger and more intense.
PAUL HUTTNER: Jennifer, we also saw those devastating floods in Europe this year. Is that the same atmospheric mechanics? Is that a stuck jet stream?
JENNIFER FRANCIS: In fact, that was. It was just of the opposite flavor, if you will. So instead of a big bulge northward, it was a big dip southward. And in fact, it dipped southward so sharply that it basically broke off and made an eddy, which you can think of like a swirl in the river that breaks off from the main stream. And once you get one of these broken off swirls, they tend to be very persistent. They tend to stay in the same place for a long time.
PAUL HUTTNER: So when we see these extreme weather swings, here's the analogy I use, Jennifer. It's like putting a little bit of water in a pot on a stove. And if you keep the burner on simmer, it just kind of bubbles along. But if you turn it up to high, the water evaporates quickly and you get into drought. But now if you add water, it can boil violently. So you're getting severe storms and floods. What analogies do you use to explain this amplification of our hydrologic cycle?
JENNIFER FRANCIS: I think that analogy that you described is a good one. By trapping more heat in the climate system, we're literally putting more energy into the climate system as well. And the Earth has to dissipate that energy somehow. And the way that it does it is through storms.
PAUL HUTTNER: Jennifer Francis with the Woodwell Climate Research Center, Thanks again so much for your perspective today on Climate Cast.
JENNIFER FRANCIS: My pleasure. Any time.
PAUL HUTTNER: That's Climate Cast. I'm NPR Chief Meteorologist Paul Huttner.