Podcast Episode 1.97

What will happen when the permafrost thaws?

Since the Industrial Revolution nearly 150 years ago, global average temperatures have increased by more than 1 degree C (1.9 degrees F), with the majority of that warming occurring since 1975. But during these recent decades of accelerated warming, temperatures in the arctic (latitudes above 66 degrees north) have have been rising even faster – nearly four times faster than the average global rate. The most readily observable impact of such intensive localized warming has been the rapid melting of the Greenland ice sheet, which is significant enough to be turning heads of even stalwart climate skeptics. But a less discussed (and perhaps even more dangerous) positive feedback to the warming planet is the rate at which permafrost is thawing due to the quickly elevating arctic temperatures.

Dr. Susan Natali, Arctic Program Director and senior scientist at the Woodwell Climate Research Center, sat down with Climate Now to teach us about permafrost: what it is, why it is disappearing, and the potentially drastic – and so far barely accounted for – impact it can have on greenhouse gas emissions. Listen to find out why tackling decreasing global greenhouse gas emissions as fast as possible is likely even more urgent than we thought.


Sue Natali
Arctic Program Director, Woodwell Climate Research Center


Sue Natali

Arctic Program Director, Woodwell Climate Research Center

Dr. Susan Natali is an Arctic ecologist whose focus on permafrost thaw is motivated by an acute awareness of the risks it poses. She leads Woodwell Climate’s Arctic Program, which investigates the drivers and consequences of rapid Arctic change. Her research examines the effects of climate change, including permafrost thaw and increasing wildfires, on northern ecosystems and the impact these changes have on Arctic residents and the global climate.

Hosted By:

James Lawler
Climate Now Host


James Lawler

Climate Now Host
James Lawler is the founder of Climate Now. James started Climate Now as a way to learn about climate change and our energy system. Climate Now’s mission is to distill and communicate the science of our changing climate, the technologies that could help us avoid a climate crisis, and the economic and policy pathways to achieve net zero emissions globally. James is also the founder of Osmosis Films, a creative studio.


James Lawler: [00:00:00] Welcome to Climate Now, the podcast that explores and explains the ideas, technologies, and solutions that we’ll need to address the global climate crisis and achieve a zero emissions future, I’m James Lawler. To sign up for our newsletter, which goes out every Tuesday morning with the link to the latestWe speak with Dr. Sue Natali podcast episode, background information and relevant links, go to climatenow.com. To get in touch with us, email us at contact@climatenow.com. We love to hear from our listeners.

On today’s episode, I’m speaking with Dr. Sue Natali, an Arctic ecologist at the Woodwell Climate Research Center about the impacts of permafrost thawing on the global climate system. But first, our news segment this week in climate news.

Now for our interview. Dr. Sue Natali is an Arctic ecologist who leads the Woodwell Climate Research Center’s Arctic Program, where she studies permafrost thaw. Woodwell Climate is a leading climate research nonprofit based [00:01:00] in Woods Hole, Massachusetts, in the town of Falmouth. The group studies and then informs policymakers on causes and impacts of climate change across the globe.

The Center was founded in 1985 by ecologist George Woodwell, who was one of the earliest voices speaking out about the threat of climate change. In 1986, George Woodwell testified along with James Hansen and other scientists before the US Senate Committee on the Environment and Public Works about the dangers of the Greenhouse Effect in one of the earliest public proceedings, bringing widespread attention to the climate issue.

Over 35 years later, Woodwell Climate researchers are still working at the intersection of climate science and public policy. For our conversation today, we’ll be taking an in-depth look at the thawing of permafrost, which despite its massive implications on the climate system, is still left out of most climate models, which is a very, very scary thing.

First, we’ll cover some of the basics. What exactly is permafrost, where is it, and how much land does it cover? Then we’ll get into its interaction with the climate. [00:02:00] How do warming temperatures affect permafrost? How much carbon does the permafrost contain, and how much could be released as the planet warms?

Finally, we’ll get into some of the implications permafrost thaw has on our lives and our efforts to mitigate the worst effects of climate change. So, Sue, tell us about your background. Describe how your career has led you to the work you’re doing now at Woodwell.

Sue Natali: I’m an ecosystem ecologist, and as, as an undergraduate, I was a biology major and I kind of like wandered around a bit because at the time I thought, well, I can either do science or I can have an impact on the world. And that was like what I thought in my mind. And so I tried to work for, you know, different nonprofits and tried to go a little bit into like, you know, the activism world. And then I got my PhD in science.

My focus was on looking at the effects of elevated CO2 on trace metal cycling. And so I was doing some work with Mercury and other trace metals and I started working the Arctic because I was really interested in biogeochemistry and so the cycling [00:03:00] of elements and that had global impacts and that took me to carbon.

I came to Woodwell because I realized that like, wow, like here was this place where you can do science and can have an impact. And that has really, really grown. I think even outside of Woodwell there’s a lot of other science and science organizations who are recognizing that science isn’t separate from the way we make our decisions.

James Lawler: Tell us about the work that you’re doing today, if you could.

Sue Natali: The work that I do focuses on climate impacts on Arctic lands and impacts ranging from local impacts to the global implications of those changes. And so that means my focus is on permafrost and also whole ecosystem changes, and so just some context, the Arctic is warming quite rapidly, three to four times faster than the rest of the planet. One of the big drivers of this is the loss of sea ice.

James Lawler: Mm-hmm.

Sue Natali: So when you have ice, it’s very light and it reflects the [00:04:00] sun’s light back out and suns energy out. When you lose that ice, it’s very dark, and then it absorbs a lot of that energy.

And so as a result you have this regional impact, and we’re particularly seeing the warming, the Arctic, especially in the winter and in the spring and in the fall, we’re seeing accelerated warming. It’s having a lot of impacts on Arctic people. So I mean, the loss of ice, in addition to the albedo effect, it’s impacting people’s ability to access food resources, people’s ability to get around on the land. And it’s also this accelerated warming is causing the permafrost,  or this once perennially frozen ground is, is starting to thaw.

James Lawler: So what is the definition of permafrost? Exactly?

Sue Natali: Permafrost is ground that remains below two degrees Celsius for two or more consecutive years.

James Lawler: Okay.

Sue Natali: That’s its definition. So it’s like anything that’s in the ground, the soil, the ice, a rock, a frozen mammoth, like anything that is in that ground is [00:05:00] considered permafrost.

James Lawler: So describe the scale of that phenomenon. How much permafrost are we talking about and why does that matter?

Sue Natali: So permafrost underlies about, you know, 15% of the northern hemisphere land area. So it underlies a a pretty large area. The impacts depend on where you are. So this is a really huge area with many, many different types of ecosystems.

Overall, about 10 or 11% of the permafrost has thawed. It’s a very difficult number to come by, I will say, right, because unlike deforestation, you can see that from the satellite, permafrost is underneath the ground. Right?

James Lawler: Right.

Sue Natali: And so we are relying on models and relatively compared to the rest of the world, sparse kind of monitoring information.

James Lawler: Now Sue, just so I’m clear, when we talk about the permafrost layer, does that begin at the, at the surface and extend, or is this below the surface and, and how far down does the [00:06:00] permafrost layer extend?

Sue Natali: Yeah, so it’s below the surface and the ground at the very surface where you have plant roots. That’s not permafrost, that’s called the active layer.

So this is the area that thaws each summer. Below that, the ground never thaws in the summertime. And so that active layer can be anywhere from 20 centimeters to a meter to two meters, and then the permafrost thickness from the surface to the bottom of it can be meters to hundreds to a thousand meter.

Like it can be quite deep. So, so again, like it’s, it’s this huge area and there’s many, many different ecosystems and the temperature of the permafrost and the thickness of the permafrost is driven by a couple of things. It’s driven by the air temperature, but it’s also impacted by the ecosystem, so places where you have very thick organic matter, peat soils, those do a really good job of insulating the ground during the summer, and so you can have permafrost in areas that are [00:07:00] relatively warm because you have this protective ground layer.

And that protective layer is really important when we start thinking about what are the processes that are causing permafrost to thaw. So it’s a little bit tricky when, you know, we say, where exactly is permafrost? Like, there are some nice maps of permafrost, but it’s, but it’s difficult.

You can’t see it from the surface. And it is starting to thaw and you can see the impacts of thaw from the surface if there’s a lot of ice in the ground, because when that ice melts, the ground collapses and it can, it can manifest in different ways.

If there’s many different types of ground ice, you can have massive ice wedges. And when those melt and the permafrost thaws and you get like this very, very abrupt ground collapse, which you can see from satellite data. You can get just a very gradual kind of sinking of the ground.

James Lawler: Mm-hmm.

Sue Natali: Which maybe is not as dramatic looking, but you know, if your home is on that sinking ground, this becomes a very, very serious problem.

[00:08:00] Or if you’re a coastal community impacted by sea level rise in the sinking ground. The other thing that happens is you can have lakes that drain essentially overnight. You know, or like in, in a very short timeframe, if you think about permafrost as this, kind of like a concrete at the bottom of a swimming pool, that then gets a crack.

So if you’re in a place that has drainage, especially in the warmer, lower latitudes of permafrost, there’s lakes that are draining out very, very rapidly, and you can see them across the landscape. Vegetation changes are happening, you know, if the ground sinks a little bit, it’s getting wetter and you’re, you’re switching now from vegetation that grows in relatively dryish grounds, although not many areas are dry, to areas that are now becoming wetlands.

James Lawler: Hmm. And so why is this, beyond draining lakes, and collapsing ground levels and the other factors that you’ve already mentioned, what are some of the other reasons that we care about permafrost?

Sue Natali: [00:09:00] Yeah, so big one is carbon.

The permafrost region stores a lot of carbon. About 1.5 trillion tons plus, I would say. And because it’s not accounting for, um, all the carbon pools, but about 1.5 trillion tons. And you put that in context, and I don’t even know if this will be helpful, but I, what helps me is just thinking it’s three times more carbon than is in all of the world’s forest biomass.

You know, we think a lot about carbon and forest and the importance of forest, and they are very important, but like every tree and every forest on the planet, there’s three times more carbon in permafrost, you know, and it’s like we just can’t see it. You can’t, you see a tree falling and you’re like, oh my gosh, we’re losing the carbon or fire, you know, forest fire.

But you know, we have all of this carbon that’s just kind of sitting there.

James Lawler: In what form is this carbon that’s stored in the permafrost? Like are we talking about organic matter that’s former roots whose decay was arrested because it, they were frozen? And then as it warms, in what ways would this impact emissions like [00:10:00] what would be the flux from the permafrost as temperatures were to warm?

Sue Natali: So it’s organic matter. Most of it is in the form organic matter. So that organic matter can be roots that haven’t fully decomposed, partially decomposed plants. It can be a whole piece of wood and it starts to get tricky about understanding how much carbon will come out and in what form.

Partly because not all organic matter is equal. And I think about it sometimes, like a banana is organic matter and a piece of wood is organic matter, right? And if you had both of those in front of you, like in, you were hungry, you’d eat the banana like right away. The wood you probably wouldn’t go after.

And same thing for microbes. Like some things they can break down really quickly. You know, like a banana, but wood’s gonna take a while. And so one of the big challenges is understanding like one, how much carbon will be released from throwing permafrost, but the timing of that carbon and the form of that carbon is co2.

So what’s happening is as microbes break down this organic [00:11:00] matter, they use it as fuel and byproducts are greenhouse gases, carbon dioxide, and methane.

James Lawler: Mm-hmm.

Sue Natali: If you are in a wetter environment, your microbes are more likely to produce and release methane and drier conditions, carbon dioxide. One of the things that makes it even more like interesting, but also complicated in the Arctic is, as I said, places that are wet now may be dry in 10 years from now, and places that are dry now may start to sink and be wet in 10 years from now.

So understanding this balance of carbon dioxide versus methane is quite tricky. And then the timing of what’s coming out is tricky because it, as I said, this is a really huge place and the quality of that organic matter is really different. It depends on how the permafrost formed, what the quality of the organic matter was when it went into the ground.

James Lawler: As the permafrost thaws do we have any idea of how much CO2 and methane [00:12:00] is being released in terms of gigatons?

Sue Natali: It might be up to about 10% of the amount of carbon that’s in permafrost. This is the place where we do have this range, so anywhere from say 100 to 550 gigatons (CO2)

James Lawler: Wow.

Sue Natali: So this is a cumulative estimate by the end of this century.

So that high end, if we take the US’ current emission rate and assume it continues to the end of the century, which it won’t, it will decrease. That high end is higher than the US emissions, cumulative emissions, would be by the end of the century, so it’s substantial. Even on the low end, we’re talking about emissions that are, you know, on par with other greenhouse gas emitting nations.

James Lawler: So I’ve heard about, you know, this, this sort of idea of a, like that this is an accelerant right to the warming of the earth, as, you know, as more release, the rate of warming increases, et cetera. Can you [00:13:00] describe that effect?

Sue Natali: As we warm elsewhere in the planet, right, like the temperature and, and the greenhouse gases are globally mixed, so the more carbon that is emitted elsewhere, the warmer it’s gonna be in the Arctic.

Then the more carbon that permafrost is gonna thaw, then that means more greenhouse gases, CO2 and methane will be released. Those greenhouse gases, CO2 and methane then contribute to more warming. The big problem here is that we are not accounting when we’re thinking about how do we stay below 1.5 or two degrees Celsius when we’re sort of adding up all of the budgets from these different, greenhouse gas emitting nations, we’re not adding permafrost into the mix.

James Lawler: Well, wait a sec. So the IPCC estimates about warming the 1.5, 2 degrees, et cetera, these estimates don’t include the effects of emissions from permafrost thawing, is that what you’re saying?

Sue Natali: So essentially. But with a caveat, I will say the last IPCC report did include some permafrost, which is[00:14:00] great.

James Lawler: Mm-hmm.

Sue Natali: Before that, it had never been in any of the climate models. So, but most of the climate models, I think there were 11, you know that went into the IPCC report. Only two of the climate models included permafrost carbon. And so when the IPCC report, it sort of uses these models that essentially kind of like averages them.

So you can imagine if most do not include a very important processes, then average, we’re not gonna be accounting for this. The IPCC report did also include a sort of rough budget for permafrost carbon emissions in thinking about our remaining carbon budgets, how much we have left is keep below 1.5 and 2 degrees Celsius.

But what’s important is that not only do most of the models not include permafrost carbon, the way that the models currently see permafrost, thawing is a gradual top-down process. So air [00:15:00] temperature, heat goes into the ground and it’s sort of gradually heating from the top layer down. The reality of permafrost thaw is that you have ice, and as we talked about the ice melts, the ground collapses.

That’s called thermokarst, but it’s essentially abrupt ground collapse. When you have abrupt ground collapses, this can accelerate thaw because now the heat can go in from the top, from the side, right? You have this disturbance, and it can, it may double the permafrost carbon feedback. So these, these abrupt processes are not in the models.

The other important thing that’s not in the model is, fire. Fire is increasing everywhere. We hear this in the news, also increasing in the north, important in northern regions because there’s so much carbon below ground. When the fire burns, most of the carbon that’s being released is carbon that’s below the ground in the active layer, these roots.

When you combust that surface, as I said, that surface is a really nice insulator in the summer, [00:16:00] so it’s essentially you combust that, it’s like opening the top of a cooler. So when you have fire and permafrost, when these are combined, it greatly accelerates permafrost thaw. And some of the work that preliminary work that we have, modeling work that we have going on in my team here suggests that the estimates of permafrost, carbon emissions that were in the IPCC report, they may be four times higher than that.

James Lawler: Wow.

Sue Natali: Because these really important processes have been left out to date.

James Lawler: So Sue, why hasn’t permafrost thawing been included in IPCC modeling?

Sue Natali: So the models, these are earth system models that inform the IPCC, permafrost wasn’t built into those models when they were developed.

Like they’re very complicated models and they are, I’m not a modeler, so, but they’re built to like, represent the entire planet. Right. That is like a non-trivial trivial to do.

James Lawler:  Right.

Sue Natali: And then these, these complicated processes disturbances, [00:17:00] abrupt thaw, wildfire, um, again, it’s not trivial. And essentially these different modeling communities really need support.

And I just don’t think right now the way science is funded, at least in the US, these relatively small grants for a small period of time just hasn’t been enough to make that happen. And so I think if there’s a commitment from funding agencies, from governments to say, yeah, we wanna, we want our models, our earth system models to truly represent important earth system processes, then there needs to be proper funding to the modeling communities in order to do this.

James Lawler: So what we’re talking about is this huge source of emissions that hasn’t really been included in most climate models to date. What are the climate implications then of, of these permafrost emissions? What do we think the contribution’s going to be?

Sue Natali: Yeah. Thinking about staying below 1.5 and 2 degrees Celsius, the amount of carbon that humans can continue to [00:18:00] release to stay below those can be anywhere from 25% to half of that, to the full carbon budget may be taken up by permafrost emissions.

James Lawler: Wow.

Sue Natali: Now, the other thing to really consider about permafrost and other earth system feedbacks is some of these things we’re committing to, right? So even when we keep ourselves to two degrees Celsius, permafrost is kind of gonna continue to thaw on greenhouse gas emissions or continue to come out and so it’s really important when we think about two degrees C, 1.5 degrees C overtopping, those temperature thresholds and coming back down, we need to come down faster, right?

Like the longer we stay above two C and that’s like additional warming that we’re sort of, buying ourselves into that’s gonna come out of permafrost thaw. Those additional years of warming in addition to the impact that’s happening, like at that very moment, [00:19:00] those are leading to increased permafrost thaw.

James Lawler: Right, right,

Sue Natali: And as you have that increased permafrost thaw, you have this additional greenhouse gases that are coming out from permafrost into the atmosphere. The other thing is, it’s not like a light switch, right? Like if, even if we did turn off our air temperature warming, there’s, there’s a lag, right?

James Lawler: Mm-hmm.

Sue Natali: Like there’s a lag in the heat transfer down into the depths of the permafrost and there will be a lag in that cooling. So you’ll still have this time period where you have this unfrozen ground or this warmer ground that can then be releasing additional greenhouse gases.

James Lawler: Right. My last question, Sue, I think, is you’re doing this incredibly important work, but it’s very depressing. It must be, like, how do you deal with that?

Sue Natali: I think, you know, you do what you have to do, right? In some ways you compartmentalize it. There’s a lot of really dedicated people who are on the front lines dealing with [00:20:00] this, scientists who are studying this.

So I think its people are very inspiring to me and that kind of like, being around those people helps a lot. It is like, yes, we are destroying the planet, but it is an amazing planet, right? And so like, what do I do to sort of get out of this is I try to just get out in the world and like you know, spend some time discovering the world and, and that kind of wonder and beauty of the earth is what keeps me going.

James Lawler: Mm-hmm. Thank you so much, Sue. That was really wonderful having you today. Really appreciate you making the time for us.

Sue Natali: Yeah. Thank you so much.

James Lawler: That was Sue Natali, the Arctic Program Director for the Woodwell Climate Research Center, discussing the impacts of permafrost thaw on the global climate system and some of the broader implications this will have on our efforts to decarbonize.

That’s it for this episode of the Climate Now Podcast. For more episodes, videos, or to [00:21:00] sign up for our newsletter or register for an upcoming event, visit climatenow.com. We hope you’ll join us for our next conversation.

Climate Now is made possible, in part, by our science partners, like the Livermore Lab Foundation. The Livermore Lab Foundation supports climate research and carbon cleanup initiatives of the Lawrence Livermore National Lab, which is a Department of Energy applied science and research facility. More information on the Foundation’s climate work can be found @livermorelabfoundation.org.

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