The connection between extreme rain and climate change in Vermont
Vermont is seeing historic rain and catastrophic flooding this week — and while the state has seen major floods in the past, this week's events are part of a concerning trend. Climate change is bringing more extreme rain to the state.
Vermont Public's Abagael Giles spoke with state climatologist Lesley-Ann Dupigny-Giroux about why this is a sign of climate change. Their interview is below and has been edited and condensed for clarity.
Abagael Giles: New England sees about 55% more extreme rain than it did in 1958. That's according to the Fourth National Climate Assessment, which you are a key author on. And certainly with this storm, some parts of the state received upwards of nine inches. So I'm curious, can we say that this event is happening to us because of climate change?
Lesley-Ann Dupigny-Giroux: One of the things that is interesting about the way in which climate change is playing out is that we learn something every day.
And in addition to the additional pieces that we learn, we can't forget about where we are — like where the state of Vermont is, and what the landscape looks like.
So, if we take apart the fact that at Vermont is very mountainous — it's got complex topography, lots of hills and ridges, which run north to south — that is always critically important when we think about how storm systems align with how the mountains align, because what we've seen in the past is if they align just right, it allows storm systems to just sort of sit in place and rain themselves out.
So, that's one piece that is characteristic of the state and why we tend to see more rain falling in certain parts of the state, certain valleys, for example, certain mountain tops than other places. So you could drive like 2 miles, and you'll be OK. I got three inches here, but two towns over we got six inches, right. And it's part of that geography of the region.
Now, the other thing that we noticed in the last few days is we all know how sticky it was, right? Now, why is that important? It's important because that high humidity, those high values, are one of the indicators that we know to be part of our changing climate. Why? Because as the temperature goes up, it causes more evaporation into the air. If you think about taking moist air and causing it to rise, there's more of it to fall out as rainfall.
The other piece that was interesting, is what we know about jet streams, and the way in which as our climate changes the direction of the jet stream — how far south it dips; like a little U before it turns and goes back up — we're seeing that sort of undulating that U shape a little bit more. And so what was actually happening, it was really interesting to watch as a climatologist to see that pattern, just sort of sit there over us.
We had practically every way that you could have rainfall getting generated, all taking place and sort of sitting over us.
So when all of those sit over us or stagnate for extended periods of time, then there's this tremendous amount of rainfall that falls out. And what was even worse than all of this is how quickly it fell out.
Last week, we were talking about drought conditions across the state. We were abnormally dry. We were actually getting into what we call D1 category of drought. And in less than seven days — because of how all of these storm systems came together, helped by what was going on at the jet stream level, aided by all the moisture that we had in place — we went from drought to this catastrophic flooding.
We had practically every way that you could have rainfall getting generated, all taking place and sort of sitting over us.Vermont State Climatologist Lesley-Ann Dupigny-Giroux
There is a lot going on here, but notably to me in that is Vermont is getting stickier. Is this pattern that you're describing something that we might see more of in the future? Are these sorts of events things that we might see more of in the future in Vermont?
Well, one of the things is we've actually seen it already — and part of the reason why there's all that moisture in the air is where the air is coming from.
A lot of the air for the last few days was actually coming from the Atlantic Ocean. Again, as a climatologist, I'm looking at these water vapor maps, and I'm seeing these nice plumes coming up from the ocean over us continually, and bringing all that that moisture towards us.
Part of the fingerprint of climate change is where the heat from the air goes — and some of it goes into the oceans and causes the oceans to warm up, which means they evaporate more, which means more moisture back into the air.
So when you hear scientists talk about a feedback loop, it's that warming, causing heating of the ocean, which causes them to evaporate more, which then causes the air to hold more moisture.
I know a lot of people — I heard yourself included — compared some of the high waters that we've seen so far — and you know certainly others are comparing the damage we're seeing — with the 1927 flood with flooding during Tropical Storm Irene. How should we understand extreme weather events in Vermont? And how do we know when they deviate from the historic trend?
So, I think one of the classic signatures of Vermont is what we call climate variability and change. Climate change in Vermont is about all peoples, and it's about all hazards.
It's water based. So we've got floods and droughts. But it's also air quality based. And that's where wildfires come in, for example, forest fires, volcanic eruptions. It's also severe thunderstorms. It's also blizzards.
And so, for me, climate change is about knowing how all of these hazards are changing, and being prepared, so that we know it can flip from one hazard type to another.
You often speak as our state climatologist about vulnerability and disparity and vulnerability when it comes to climate change in Vermont. And I'm curious, in light of this recent flooding, due in part to climate change, who in Vermont, what parts of the state are our most vulnerable as we move forward?
If we use the flood of last couple of days, as an example, I think it's what we've seen in the past — which is if you live close to a water body, if that water body exceeds its banks really quickly, like in a flash flood — living along or close to a water body sets up vulnerabilities.
They're also vulnerabilities from a social perspective, from an economic perspective — homes that are located in places that are closer to the regions that are vulnerable from a geographic perspective.
Everybody has a different level of vulnerability. So we're all vulnerable in some sense. Some folks are just a little bit more vulnerable than others.
Housing insecure peoples are also vulnerable, and takes it one step further from a linguistic or language perspective — because when we put out alerts, when we put out warnings, how many languages are we using to put those out in?
What can we do about all this? What can Vermont do to adapt? And what does that look like here?
So, one of the things that came out in the Climate Crossroads, launched today, that the National Academies of Sciences, Engineering and Medicine were talking about, is we need to do things differently. We need to do things differently. We need to do things differently, now. How do we get all the sciences, all the engineering, all the policies, all the everything in the same room to actually work with people's so that everybody is able to be OK, whatever that might look like. And so it's a different paradigm from what we've done in the past, and I think it's the only way that we're going to make forward progress.
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