Beyond 1.5 Series | Tipping points: Is there a point of no return?

Welcome everyone to this second in our Beyond 1.5 series this fall. I'm Heather Goldstone, Chief Communications Officer at Woodwell Climate Research center, and I'm thrilled to be with you this afternoon. It was a pleasure to welcome hundreds of you to our first event in this series two weeks ago. And I would love to see if you can find that little raise hand, the little hand icon down at the bottom of your screen. Raise your hand if you were with us for that first event two weeks ago. Fabulous. The numbers are ticking up here. We've got at least several dozen folks who were with us the first time around and here today, which is great. These events really have been planned as a series and you can go ahead and put your hands down or we'll do that later. Don't worry about it.

Really.

Planned as a series, these events are meant to walk us all together through a process of confronting the full magnitude of the climate crisis that we currently face, the risks and also the choices that are in front of us in a rapidly warming world and as we race to restore a safe and stable climate. The goal is not to leave this process or come out of this process feeling overwhelmed and depressed, but rather motivated with an increased sense of urgency and ambition and vision for where we could be headed. That's the solutions part of the equation will come in the next few events that we have today. We're going to continue the process that we started with our first event and looking at some of the really critical risks that we face to help us understand the problem that we face. Because of course, if we don't understand the problem, we can't craft effective solutions. Before we go any further, I would like to thank the K? Neb family for their support of this series. Of course, while we all enjoyed and many of us miss gathering for in person events, we do recognize that these virtual events give us an amazing opportunity to bring more diverse and more far flung groups together, both in terms of our panelists and in terms of you, those who are able to join us for these. So we really appreciate the support of the Knab family in helping us make these possible. And I also want to acknowledge that I'm speaking to you today and that Woodwell Climate Research center is located on the traditional and sacred lands of the Wampanoag people who have lived in this place that we often call Cape Cod for thousands of years and whose language, culture and traditions continue to be a vibrant part of our community. Woodwell Climate also recognizes, of course, that Indigenous leadership, knowledge and stewardship are invaluable in the global effort to restore a safe and stable climate. As I mentioned, today's conversation will delve into what panelists actually in our first event highlighted as one of perhaps the greatest and perhaps most under recognized risks and challenges in our effort to restore a safe and stable climate. And that's often what's called tipping points, points of no return. In addition to the increasingly obvious impacts of climate change on society in our daily lives, from heat waves and fires to floods and hurricanes, global warming driven by greenhouse gas emissions from human activities are also changing the natural world and threaten to set in motion processes that can become self feeding, that are often called vicious cycles or feedback loops. And the impacts of these feedbacks can essentially irreversible on human timescales, meaning it would take a very long time to stop or reverse some of these processes if they reached a certain point. But pinpointing where those points are exactly is no simple matter. And the whole issue of tipping points in climate change remains a matter of considerable scientific discussion. We've all heard Greta Thunberg at the UN a few years ago talking about tipping points and feedback loops. She also tends to call on us to listen to the scientists. So that's exactly what we're going to do today. And in the next hour specifically we're going to hear from our three panelists, two of whom are from Woodwell Climate and one from our close neighbor down the road, Woods Hole Oceanographic Institution. I'm going to introduce them extremely briefly and then let them actually introduce their work. The three of them are experts on very different systems, very different parts of the world, very different parts of the climate system, although that share this common point of the discussion about tipping points and where going past a tipping point might land us. One of our panelists, it seems has actually just stepped away for a moment. So hopefully Sarah Dass will be back with us in a moment. That's Dr. Sarah Das, an associate scientist in geology and geophysics at Woods Hole Oceanographic Institution who studies polio polar ice sheets, obviously a critical part of this conversation. So hopefully she'll be rejoining us in just a moment. But still with us, Dr. Sue Natali, Director of Woodwell Climate's Arctic Program and a real pioneer in studying Arctic permafrost. And also Dr. Mike Koh, who leads our tropics program and has been studying the Amazon forests for decades now. So thank you both for being here. And Sue, I'm going to hand it over to you to introduce us all to perfect permafrost.

Okay. So I'm going to provide a really brief overview of feedbacks and tipping points from permafrost thaw. This is going to be a quick overview of permafrost and some of the impacts of it thawing. If you want more information, we can talk more about it on this panel. Also you can go to the Woodwell Climate website. And we also have a new website called unstableground.org that focuses specifically on climate changes in northern regions. So just I feel like most people probably already know what permafrost is, but for those of you who don't, it's perennially frozen ground, so it does not thaw in the summertime. It's located in the polar regions and in mountain regions and it's any material that's in the ground. So it can contain a lot of buried ice. You can see that as a shiny areas shown in this hill slope exposure also contains a lot of carbon in the form of frozen organic soils. Okay, so this is just a map showing the distribution of permafrost in the northern region. It's fairly widespread, so all the areas shaded into blue. This is the northern permafrost region. It's almost twice the size of the United States. Much of the permafrost in the US is in Alaska. Russia and Canada also contain large amounts of permafrost. So it's a fairly large area. But the area where there is permafrost is shrinking as a result of climate change. The Arctic is warming three times faster than the rest of the planet. And this is having an impact on the distribution of permafrost. By the end of this century, the permafrost is thawing. Now we expect 30 to 70% loss. And that wide range is driven by human action. And so if we continue on our current greenhouse gas emissions trajectory, that's the 70%. So we'll lose more than half of the near surface permafrost. And we can cut that in half by greatly reducing our fossil fuel emissions. So that's a problem for the people who live in the Arctic because permafrost provides support for infrastructure and for homes and for habitats that people rely on. But it's also a problem for everyone on the planet because the permafrost stores a lot of carbon. Current estimate is about 1.5 trillion tons of carbon is currently contained in permafrost. That's two times as much carbon as is in the Earth's atmosphere and three times as much as every tree in every forest on the planet. There's a Lot of carbon there. This is the reason why it's a problem, because once as the climate warms, the permafrost is thawing. Once that permafrost thaws, that carbon, which was in the form of frozen organic material, once it thaws, it then becomes available for microbes to use. They break it down and they release greenhouse gases, carbon dioxide and CO2 and methane, CH4. And one thing I want to point out, so this is an amplifying feedback loop, or sometimes called a positive feedback loop. But one thing I want to point out is that right now this arrow is going one direction. So we're warming the climate, we're increasing permafrost, leading to more, you know, that will lead to more warming. The arrow can certainly go in the other direction. So if we cool the climate, it is definitely feasible that permafrost can refreeze. But the important thing to keep in mind is that the carbon that is contained in permafrost took tens of thousands of years to accumulate. Releasing that carbon over a year, 10 years, 100 years into the atmosphere is essentially making that carbon irreversible. The uptake of that carbon irreversible. On a human relevant time frame, it's not impossible. But it's important to keep in mind that the timing of these processes then the other important thing to keep in mind about permafrost thought is yes, indeed, the ground can refreeze. But what often happens is something like this. So this was a relatively flat forest where I work in Siberia. As a result of permafrost thaw, all that ice in the ground melted and the ground collapsed. And you see there's no longer living trees in this forest. There's some grasses recovering, but much of the soil, a lot of the organic material was eroded and washed off and eventually emitted into the atmosphere. So when we think about whether this is irreversible, the time scale and also the spatial scale of the processes are really important. And finally, just one last slide and just how severe how much carbon will be released into the atmosphere. While there's some uncertainty around this, the number can be quite large. So if we continue on our current greenhouse gas emissions trajectory, it might be equal to 150 billion tons cumulative by 2100. And just to give you some perspective, that's on par with the current rate of US emissions. So if US continues on their current emissions through 2100, this is about how much we can expect to see from permafrost. So it's not a trivial amount and it will contribute to increased warming. With that, I'll stop and pass it back to you, Heather.

Great.

Thank you so much, Sue. I was looking at that picture of the forest you just showed there, and those of us from New England are familiar with frost heaves, but that's a whole other level of, of upheaval due to thawing and freezing. Thank you for taking us there so we can actually have a better sense of what it looks like on the ground. I want to turn next to Sarah. We're going to stick with the cold polar regions of the world for the moment, but a very different type of feedback loop and very different system involved here. Sarah, introduce us to the ice sheets that you work on and this issue of, of tipping points and feedback loops and how that comes through in the work that you do. And I'm going to share my screen here with Sarah's slides. So just give me one second to do that.

All right, great. Thanks, Heather, and welcome, everyone. So, as Heather mentioned, I'm Sarah Dass. I'm a scientist at the Woods Hole Oceanographic Institution, and I work on the large polar ice sheets that you find in the Arctic and the Antarctic. And those are illustrated here just to give you a sense of the kind of places I'm talking about. So, on the left, we have the large polar ice cap of Antarctica, and on the right of Greenland. These are both large islands that are covered with ice over 2 miles thick in many places. And these ice sheets represent a huge reservoir of fresh water, together enough to raise global sea level more than 200ft. Heather, if you just click once more, you'll see there's a short animation that will start now. You're looking at the seasonal view around both poles, and what you also see changing is the snow and ice cover and the sea ice cover. So the large ice sheets are stable, relatively stable on a seasonal scale over time, but you also have these large seasonal variations, in particular in sea ice. On the left, you'll see Antarctica, which has the waxing and waning of sea ice as it grows out into the Southern Ocean and retreats back each year. On the right, around Greenland, you'll see the waxing and waning of the Arctic sea ice, which fills in and then retreats across the Arctic Ocean. I draw that to your attention just because sometimes there's a little bit of confusion when we talk about polar ice or ice sheet collapse, whether we're talking about the large land continental ice masses or sea ice. Go forward to the next slide. Heather, could you. There you go. Thanks. So the Polar ice sheets that we saw in the Last View are a really critically important part of the Earth system. And while much of the focus, rightly so, is on their contribution to sea level rise, and that's mostly what I'll be talking and discussing a bit about today. In terms of tipping points, it's worth pointing out that the large fluxes of fresh water that come into and out of the, in particular out of the ice sheets is also really critical to other parts of the Earth's system. This large freshwater can affect ocean circulation and ecosystems, and then it's really intimately connected with other parts of the Earth system. But what I really want to drive home today is this point about the rapid changes that we're experiencing now in the polar regions. In both Greenland and Antarctica, these ice sheets are rapidly melting. So they're losing more ice each year than they're gaining through snowfall. There's a lot of talk, and we'll focus a bit today on whether these ice sheets are at a tipping point or approaching a tipping point. And there's many ways to think about that. But for the most part, we see the loss of this ice as irreversible and accelerating over time. There's two main forcings behind this loss of large polar ice. One is through the warming of the atmosphere, and the other is through the warming of the ocean. We're attacking these ice sheets from both sides. We know the Arctic and the Antarctic are warming up, and as the atmosphere warms, you have more and more melt that contributes to the melting away of the surface of the ice and that run off into the ocean as the ocean warms. Any place where you have ice in contact with the ocean, so around the edges of the large ice sheets, you have this warm ocean water eating that ice away. Now, those things on their own are not examples necessarily of critical thresholds of tipping points, but what we start to see happening, this is illustrated in this now iconic image on the left, which is now almost two decades old. This collapse of the Larsen D ice shelf, this is a floating portion of glacier ice in the Antarctic Peninsula, is that sometimes this loss of ice is very rapid and dramatic. It's not just a slow eating away. This is an example where you had a bit of surface melting or ponding on the ice shelf. It was able to crack apart or hydro fracture the entire ice shelf. And in the course of about a month, this entire ice shelf splintered apart and floated away. It's on a loop, as you'll see. The loss of an ice shelf itself isn't necessarily going to raise sea level, but it has a lot of other effects on the ice flow behind it. And we can get into that later. On the right, you'll see a sort of cartoon view which is an example of the dynamics that we're concerned about in large parts of West Antarctica. This is a cutaway view of a glaciers, for example, like Thwaites Glacier in West Antarctica. What you see here is that this ice sheet is entering the ocean, has a large tongue entering the warm ocean. And this ocean water is eating away at the base of the ice. The ice breaks apart and retreats over time. But because the land inland, as you go into the interior of Antarctica, gets steeper and deeper, the more ice that you eat away at the flower front, the faster the ice that's behind flows into. And so you create this runaway effect, this marine, what we call marine ice sheet instability. And so the more the ice is lost, the faster it flows, the faster it stretches and the more quickly it's lost and it builds upon itself. And so this is a dynamic that we're very concerned about in the West Antarctic in particular. If you go to the next image. So this is not a polar ice sheet. It's very hard to wrap your mind around. I find the loss of a large polar ice sheet because it's so vast, this is something to just make you go, oh, or wow. Or oh, no. This is an example of a mountain glacier. So this is a small ice cap on top of Mount Kilimanjaro in Africa. What you see illustrated on the right is over the course of just a decade or so, most of this ice cap has disappeared. This is due to the warming and drying out of this region due to climate change. This is being experienced all across the globe with smaller mountain glaciers and ice caps that are retreating and disappearing very quickly over the course of the 20th century. That was actually a fairly large contributor to sea level rise. The larger polar ice sheets are now eclipsing that. On the left is this iconic image of ice climber Will Gad, who has returned to Mount Kilimanjaro multiple times. And this is really just an example of the last bit of a glacier in demise. And we're not going to see this in the Antarctic or in Greenland, but this is where we're headed in some ways. And this is where very many mountain glaciers that are disappearing are headed. And so if something sticks with you in the back of your mind about what an irreversible loss of ice is, maybe this picture will next one. Another way to think about the loss of ice is towards commitment points. And so we'll be discussing that a bit in this conversation whether we should be thinking about these tipping points or commitment points. But what we're really trying to illustrate here in this map view, this is the results of a modeling study from a couple of years ago is that the extent of a big ice sheet like Greenland is very sensitive to the warming or emissions pathways that we're on. And that's where we have a lot of control. This is the kind of figure that if anything, should give you hope or make you want to take action. So this is a view modeling Greenland out just over the next thousand years. And what you see is under various emissions pathways 2.6, which is sort of the Paris goals, up to 8.5, which is kind of sometimes called business as usual or the course that we're on. The shape and size of the Greenland ice sheet changes dramatically from what looks like a little bit of retreat towards pretty much almost entirely lost. Next slide. And I want to end on. Heather asked us to kind of imagine what does a world pass a tipping point, in this case, world without ice look like. Of course, the major consideration when you lose all of polar ice is sea level rise. While we're not headed directly towards a world with no ice, this is an example. We experience sea level rise locally or regionally, not globally. For those of you that are tuning in from the East Coast U.S. or northeastern New England region, this is a map view of southern New England. And it's just illustrating that once you take away all of the ice, the scale of change that we are headed towards, this is an extreme example. I don't believe that we're on course to melt all of the polar ice sheets, but I don't know that that is much cause for comfort. What you see here is all of Cape Cod and all of the major cities underwater. But we don't need to melt all the polar ice to really cause dire harm to the world. More than 600 million people, so 10% of the world's population live in coastal areas less than 10 meters above sea level. And that is on scale with the loss of Greenland and Antarctica pathway we are very much headed down today. And I would argue that how fast that happens is still up to us.

Thank you, Sarah. Okay, so just within the polar regions, two very different processes going on with permafrost thaw emissions from that potentially feeding runaway warming. In Sarah's case, the processes that drive ice sheet melting, the possibility there of runaway melting and extreme sea level Rise. And now we're going to shift gears perhaps even more dramatically and head to the tropics, to tropical forests, and hear about the potential tipping points and feedback loops that are of concern there. Mike, I will hand it to you.

Thank you, Heather. Yes. So I would just very briefly talk about tropical forests and why they're important for the climate and why we're worried. This map shows. This map is carbon or biomass above ground biomass. The darker green it is, more biomass there is. And what you see right away is that the tropics, the tropical forests, contain most of the more than half of the above ground biomass on the planet. So that's the, the biomass in trunks and limbs and leaves of trees. This is where I and my team work is in the Amazon and in Congo in particular. These forests contain a huge amount of biomass and when we think about that, they're actually really important part of the climate system, because these forests are actually an enormous collection of factories. Each tree is a factory. And each tree, what it does is it soaks up sunlight and takes energy and pulls in CO2 and it expels water vapor. Basically, they're pulling the CO2, they're using energy to create wood and create sugars, and they're expelling water in the process. And they do that 365 days a year. So forests in the higher latitudes have a much shorter growing season and therefore do this only a short period of time of the year. But tropical forests do it year round. That has really important implications for the climate when you think about it. So what are they doing? First of all, they soak up a lot of carbon. When we look at this, when we look at tropical forests, in total, they're responsible for something like 20% of all gross CO2 uptake each year on the planet. So they're taking up essentially 20% of what humans are putting in the atmosphere every year. So they're providing this enormous climate service of taking carbon out of the atmosphere. They do a lot more for climate. They, they produce water vapor, so they make it rain. They make an enormous amount of rain. They produce water vapor on a huge scale. One tree can, one tree in the tropics will expel something like 500 liter, 500 liters of water a day. All that water moves around and just creates rain all over the planet. They also cool the planet. Trees are essentially a giant air conditioner. By soaking up the energy and expelling water there, they're cooling the surface. We see in the Amazon and in Congo, if you cut down the forest, you essentially instantly change the temperature by 10 degrees Fahrenheit or 5 degrees C roughly for that location. It's a permanent change in temperature as long as you don't have those trees there. And that adds up when we look at the global temperature, the tropics, those forests cool the planet by about 1 degree C or 2 degrees Fahrenheit. And said another way, if we lose those forests, we're warming the planet by 1 degree C because we lose these services, we put carbon in the atmosphere and we lose the air conditioning. So what is happening when we deforest as is occurring in the Amazon and as things get warmer? As I said, first of all, it gets extremely hot when we deforest 10 degrees C or 10 degrees Fahrenheit, right away rainfall decreases. What we see is the dry season gets longer. These two changes have huge implications for the remaining forest because what they do is the extra heat and the lack of rainfall leads to more frequent fires and just mortality in general of the remaining trees. And that leads to grass invasion, which leads to more fires. And it's a cycle by which the edges of the forest degrade and the edges move back into the healthier forest, continually degrading the forest as it goes. The problem, when you think of this in the larger scale, the cycle feeds on itself. When we think of this in a larger scale, the problem begins to occur. We have an enormous amount of deforestation and we have a climate that's changing, that's getting warmer just from the external, the CO2 problems, when we think about that, and we have this continuous degradation, there's something like in the southeast Amazon, there are tens and tens of thousands of kilometers of edges. And each of those edges is long run. What we've seen there is a very large area in the southeast Amazon is now, is now degrading in place and becoming less and less like a tropical forest. It has less biomass in total. It's putting more carbon in the atmosphere. It's in fact releasing more carbon to the atmosphere than it's soaking up. So some of these forests have already tipped over to sources of carbon rather than sinks. And this is just a picture of what a heavily degraded forest looks like. This was never logged or cut down. This is just cyclic fires and heating have resulted in a rainforest turning into essentially a savannah. That's what we worry about on the much larger scale. Thank you.

Thank you all for that whirlwind tour of some of the most important systems within our global climate system. And some of the risks that we face as these systems change in response to rapid warming. Of course, the title of this event was Tipping Points. And we posed the question in the title, are there points of no return? I guess the main question really that I want to get a response from each of you on is, is this framing of tipping points a useful one? These are all systems where that language is frequently used. Is it really a useful framing for thinking about what is happening in these systems? Or is there perhaps a better way to think about the ongoing processes and changes happening in each of these systems? Mike, you are next to me on my screen, so maybe I will throw that to you first.

Thanks. That's one of those tipping points have been discussed in the Amazon in particular for a very long time. The idea that if we deforest too much of the Amazon, the climate will change enough that it'll no longer grow back.

We'll lose the rest of it and it.

Lose the rest of it. Yeah, I'm sorry. If we deforest enough rainfall changes, we lose everything. I'm less worried about that kind of a scale. I think that, you know, I think that's less of a worry if the climate were not changing. But. But I do. But we certainly see in, you know, for example, the southeast Amazon where we've. We've changed the environment enough that the forest is now by itself shifting into something else. It's shifting into something that's more reminiscent of a transitional forest or even a savannah. And that is something that on our timescale, if we do not control things like deforestation and fire, is not reversible.

So maybe not a global tipping point, but regional tipping points happening throughout the larger area of the Amazon.

That's how I tend to think of it. Or in other tropical regions, it's more of a regional because of the external pressures are being put on it.

Sue, that's something you already hinted at in your presentation as well. This idea that when we're thinking about how permafrost is changing, that both timescale and spatial scale are really important factors. Global tipping point, yes or no. And how do space and time play into your thinking on that?

So I, yeah, I say I don't find tipping point the most useful way in thinking about it. I'll start with that for a couple reasons. One is just because it's not exactly. It's not exactly how the world. How the world works or the ecosystems function. Right. And the Arctic is a huge place and so there's not a tipping point. And also I'd say As, as, like how humanity works. Right. I mean, so there's things that are happening in the Arctic where you're releasing greenhouse gases into the atmosphere, but that's not happening just in its own world. Right. It's this connected world. So what happens with that depends on what happens in the tropics and in our response to it. So globally, if we got to a point where like, there was no way we could stop permafrost thaw and that was leading to increased warming, we have a lot of other problems. I don't even know if we'll be. I mean, honestly, like, we're at 1 degree warming right now and there's huge problems on the planet. And so I feel like, you know, when I showed you, okay, at, you know, at our current trajectory, we can expect, you know, maybe up to 150 billion tons of permafrost carbon emissions to be released. We don't want to get there and we don't want to get worse. And so. And then in terms of this timescale. Yeah. Like, is it, you know, is it irreversible? If carbon goes into the atmosphere, it can be taken up by a plant and then fixed again and wind up in soil and perhaps soil in the Arctic. And if we cool, then it could become permafrost. It's just that arrow of, to reverse the arrow, it's quite a bit slower. It took a really long time to get that carbon into the permafrost. And once it's in the atmosphere, it's not really reversible on human relevant timeframes. And then as I show you, saw in that picture, some of the processes on the ground, there is a regional tipping point. That place is never going to be a forest once the ground collapses in these extreme events. Like, it's not, I don't want to say never, but in the timeframe where humans will be here on this Earth, that regional impact is irreversible.

And Sarah, how about with ice shelves? You used a phrase in your presentation, commitment points maybe a little bit different than tipping points. Is it a similar, you know, hearing kind of a similar refrain from, from Mike and Sue here, that single global tipping point is maybe not the way we should be thinking about this.

Yeah, I think that's true. Across the different systems that we're all studying, even though they're all quite distinct in terms of the ice sheets, there are certainly tipping points or instabilities that are inherent in the physics of both the Antarctic and Greenland ice sheets. And as you know, sort of a scientist or a model or looking out over long terms. These are useful things to understand and we're spending a lot of effort trying to understand them. So I'll start by saying there is a use for them. I want to echo Sue's point. You know, what is though, the space and time scale that we're interested sort of on the human relevance side. So in the case of something like West Antarctica, where we have this marine ice sheet instability, you know, the best models and, you know, this is a moving target, but we're narrowing towards the target, suggests that there's a big difference between, you know, a 1.5 degrees rise versus a 2 degrees rise in terms of which side of that threshold of instability we end up on and whether the West Antarctic ice sheet enters a period of unstoppable retreat, which would add three or more meters of sea level, which is a lot that is important. On the other hand, in Greenland, we don't have this collapse or unstoppable retreat, but we have something called the melt elevation feedback. Again, we do think that there is something in the physics there where as you warm and melt Greenland, Greenland is high and cold in the center because the ice is thick. It's not because it's sitting on top of the mountaintop. The more that you melt Greenland, the smaller Greenland becomes. Now you have parts of the ice sheet that used to be cold enough to have snowfall that are now receiving rain. You may have heard in the news this summer, there was quite a bit of news about the fact that there was rain recording recorded for the very first time in history at the summit of Greenland. So over two miles high on top of Greenland, it was raining. This shouldn't be happening. Hasn't happened before. If it starts to rain on Greenland instead of snowing, you're going to rapidly lose that ice. And if you get the ice to a low enough elevation where it's going to be receiving rain rather than snow, it's really. That's going to trigger this threshold as well. So I think those are important points. On the other hand, the total loss of a part of West Antarctica, of Greenland, this is this kind of looking out, the thousand plus year view, you know, are we on the pathway to that? I think is somewhat less useful because we don't need to be past the point of no return to lose all of Greenland to be very concerned.

I think that's a really great point. And I see sue nodding and there have already been a handful of questions which, by the way, feel free to add questions, preferably if you could put them in the Q and A rather than the chat. So the two little thought bubbles, as opposed to the single thought bubble icon down on the bottom of your screen, that would be great. And I'll be looking through there. We probably won't address a lot of individual questions, but looking for themes that would be helpful to highlight there. So please do add your questions there. And one theme that's already come out is like, well, okay, but does that mean we shouldn't be worried and people actually voicing a concern that if we say there isn't a tipping point, that that might give licensed people license to not be so worried? That's not what I'm hearing from you guys. In fact, we got together last week to kind of talk through some of this and actually came up with an alternative analogy, I guess, for what's happening in these systems. As opposed to a tipping point being like going over a single cliff. You guys said, maybe it's more like we're falling down a set of stairs. And like in a video game, the stairs above you are kind of disappearing as you go. So it's not just a single fall, but you're also talking about being on a pathway to the bottom of the stairwell, and that's where we don't want to end up. But you've also really been highlighting that this is not yet fully committed and the importance of the choices we make now. So maybe we could just go back and reiterate, like, what is the path in each of these cases that we are on right now, and how much can we deviate from that path with the choices that we make about human behavior right now?

I can jump in a bit. I really liked when we were discussing earlier this staircase idea because I do think there's a concern with the tipping point being this cliff, that it's really an either or. Either you get to the edge of cliff and you somehow stop, or if you've gotten too far, you know, this idea that if we don't meet some target by next year or by 2030, that we, well, we might as well just fly off the cliff. I mean, that to me, is absolutely the wrong approach. You know, we are racing down the stairs and there is irreversible loss at every stair that we race down. But what stair we end up, the bottom stair we end up. Whether it has to do with how much sea level we're committed to, how much permafrost loss, how much Amazon lost is entirely within our control. Just as this example with ice loss illustrates. If you reflect back on the image of Kilimanjaro. I mean, pretty much that's gone. We've lost that ice. We've lost many mountain glaciers. But for the large polar ice sheets, everything is really within our control. And the best models do suggest that which side of the emissions pathways and this temperature, whether it's one and a half degrees or two degrees, is a critical difference in terms of starting to run faster and faster down the stairs to the point where we end up on a lower stair, more committed sea level, or whether we can slow that down.

Yeah, I really agree with that. You know, when you look at the Amazon, we've hit a 1 degree C. You know, the planet's 1 degree C warmer, a bit more than that, and we've already lost a significant, you know, we've already really altered a significant fraction of the forest.

Now, to be clear, Mike, in your case, that's a combination, right, of climate change and direct human action of deforestation, right?

It is.

That's a little bit different than something like that.

It is different. And that's where, you know, it can be more complicated there because we have these two things. Two. We have get humans in there cutting things down and lighting fires, and we've got a changing climate that makes those fires worse and worse. So with one degree, we've already put a dent. With two, I would be, you know, you can look at. I look at that and say, am I going to lose 40% of the Amazon? I might. And do I want that? Absolutely not. So we can stop deforestation and we can stop lighting fires, and that's going to go a long way to help the Amazon, but we're still going to lose some if we continue to warm the temperature.

And of course, as you mentioned, stopping deforestation will also help us with slowing the global climate change. There's two steps or two decisions and actions we can take to slow that descent down the stairs there, which is stopping deforestation as well as stopping greenhouse gas emissions. Sue, I want to make sure we let you jump in here as well.

Yeah, just real quickly, I'd say. I think as you get farther down that staircase, this gets harder and harder to slow your speed of your speed down. So it's not linear about, you know, yes, we haven't gone off this cliff, but it. There is more urgency than the cliff because the longer you wait, the harder it gets, right. The more we've committed, the more we're having, you know, increased fires, which are, you know, adding greenhouse gases to the atmosphere, which in the north are also thawing the permafrost. And so. And it does seem, as the more we learn, there are more kind of surprises, there are more nonlinear events than I think in not all of the cases, but in many cases than we knew about. We're going into a new world that science really hasn't been in before, humans haven't observed before. And so unfortunately, it doesn't seem like things are going in the slowing down direction. It does tend to seem that things are going speeding up direction. So to me, there's more urgency because I don't want any more surprises. Right. I mean, we've had enough and they're not good.

So surprises. So.

So Sue, I want to follow on that and a couple of questions that have showed up in the Q and A and the, the chat. And that has to do with the, the difficulty actually of gauging where we are on that staircase and how quickly we're moving. I mean, this is a huge challenge for permafrost in part just because it's such a huge area, but give us a fuller sense of why is it so hard to figure out exactly where we are on those stairs, how quickly we're going down or how quickly we will end up going down.

Yeah. So, I mean, the Arctic is a huge area and it's hard to access a lot of it. And there's multiple countries that comprise the Arctic and there's multiple different types of ecosystems. And the monitoring of carbon emissions or carbon fluxes, so uptake and loss are. The exchange between the biosphere and the atmosphere are quite low in the Arctic. And our spatial distribution of monitoring is quite low. Our temporal distribution, we go up. Scientists tend to go up to the Arctic in the summertime when it's warmer and light out. And then we leave in the winter. But the world microbes are so active in the winter. And so there's a huge gap in our monitoring. And even knowing the carbon balance of the Arctic right now, a lot, a lot of uncertainty getting that information into models and getting global models to function and to incorporate permafrost in them. You know, they weren't developed for northern regions. You know, they weren't calibrated further north. And so even when permafrost is represented, the processes are represented in the way that we know that they're happening in reality. And then it's like getting that information out to people. You know, we do know something. And then there's this other sort of challenge of getting that information out into the world. When we think about globally we're counting for the different nations how much carbon we're emitting and what our commitments are to stay below 2 degrees Celsius. We do have some sense of the range of how much carbon can be released from the northern region, but that's not accounted for in this global bookkeeping. Our efforts to stay towards 1.5 or 2 C just aren't even accounting for permafrost. These are some of the challenges of just increasing what we know by monitoring more and getting that into the model so we can could project into the future and then also getting that information into the people who need to make decisions based on it.

Sarah, I would assume that when it comes to things like the ice sheets of Greenland and Antarctica, there are plenty of logistical as well as scientific hurdles to really pinpointing where we are and where we're headed.

Yeah, absolutely. I mean, following on Sue's point, of course, these regions are very difficult to access and tricky to work in. Fortunately, over the last couple of decades, the ability to observe the changes in ice, polar ice, using satellites has really exploded. And so we have a very brief window of observations for this observational era where we can use high precision satellite observations to do things like gravimetry to actually weigh from space the amount of ice over Greenland or Antarctica. And we can also do things like use altimetry to see how the surface height has changed over time. And we can measure spatially the growth and shrinking of the edges of the ice. So you can combine all those methods and you can get over a couple of decades, kind of pretty good sense for where we're at. But of course, that's not even the blink of an eye in terms of the timescale of change. To get further perspective where we stand today, we need to use more geologic or paleo paleoclimate tools. And one of the ways that my group has really contributed to this is using ice cores. So we can actually then extend this very brief observational era and go back hundreds of thousands of years and say, well, how, for example, has Greenland been growing or shrinking or melting over time? One of the alarming things that we showed in a paper a couple of years ago is that this again gets to Sue's point that the staircase is not even. So this melting that we're seeing, this runoff from Greenland that we're seeing is in response to warming is very nonlinear. And so we're able to show over now a multi century period that Greenland is melting and losing mass exponentially in response to this warming, rather than in a Very steady way. But it's true that we need to place today's observations in the right context. I would argue that we really also need to expand our knowledge of the past so that we know how ice has behaved on longer timescales. Because these ice sheets are not, especially the large polar ice sheets, they're not responding day to day or even year to year. There's a lot of noise in the weather that we experience each season. In order to really understand their response to climate, you have to average over many years. Because our satellite observation era is really so short. We need these longer scale geologic observations to help us understand the behavior of into the future.

Mike, I want to turn to you. I once had a fisheries scientist say to me, counting fish is just like counting trees, only they move and they're hidden under the water. The implication being that counting trees is easy because they stand there and you can just see them. And yet you're saying there's very active discussion about whether or not there is a tipping point. We're at the tipping point, what the future of the Amazon is. So what are some of the challenges there in figuring out exactly what's going on?

Yeah, you know, like anything, you know, tropical rainforest, it's a challenging environment. First of all, you know, until recently it was a lot of these places were tough places to go to study. And you look at, it comes down to things like, you know, there are all kinds of, we have all kinds of models that try to model how forests will respond to changes in climate. The problem with that is the models just don't have the processes in there because in part we don't understand what actually kills the tree. That sounds odd, but what is the event that results in mortality for a tree? That's really not even well known. And of course it will change depending on the conditions. You know, there are several different things that could kill it, but the actual mortality, it's not well known. So you don't really. So then if you can't, if you can't model how a tree dies and what regrowth would be, realistically, then you really don't know where that edge is going to be. It's things like that and extreme, you know, and a lot of this occurs because of extreme events and extreme events. This gets back to the points that have already made. These things are changing in ways we didn't know they would change. We just had what amounted to a severe drought in the Amazon this year because it was much, much hotter than normal. The rainfall was actually normal in Much of the Amazon, but the temperature was much greater, up to 2 or 4 degrees C greater. That puts, that is stressed just like a drought. And so trees will die because of that. And again, we didn't. That wasn't something that's really well accounted for. I will, the last thing I'll say about that though is I always like to, you know, so there's a lot of uncertainty, but I, but I really like to say, you know, don't let the uncertainty get in the way of action because I know what the outcome is if I do nothing, I'm going to end up with a terrible situation. If I do something, it will be better. That's really all I have to know at one level.

And that's exactly where I was about to go with my next question. Right. Is, is okay, there are uncertainties. We're not entirely, you know, we don't have a crystal clear vision of what that staircase below us looks like and.

How quickly we're going down it.

But we know enough to know that we are accelerating down that stairwell and we don't want to go any further. And sue, you alluded to the fact that it would be possible if we cooled the planet to run that cycle in reverse. I wonder if each of you could just offer in your mind what is needed to stop that accelerating descent down the staircase and what are some of the best opportunities or mechanisms we have at our disposal to actually accomplish that.

I can start off so I think in addition to running it in reverse, we can also halt it. So we've already committed, you know, permafrost is already thawing. We've already committed, say to 30% of it thawing, but that's a lot better than 70%, particularly if your house is on that, you know, 35%, you know, that's going to take us over the edge. So we definitely can take actions. One of the problems with greenhouse gases is because they're global. What happens in lower latitudes makes its way up to northern regions. But one of the benefits of greenhouse gases is that they're globally mixed. What happens in lower latitude countries also impacts northern regions and vice versa. We can stop things by reducing greenhouse gas emissions. And I think, you know, what does that mean? It means protecting tropical forests can also then protect permafrost thaw. And it means like, yes, our individual actions matter, but I think right now we need to act so fast that we should be taking action and demanding action from leadership of our countries, of our, you know, of the businesses that we work with, like there's, right now, there's really no excuse and we just don't have time to wait because the longer we wait, the worse it gets, the more we've already committed ourselves to. And so it's much harder to go back than it is to stop. And so I think, you know, in terms of permafrost though, I think the major, major action that needs to be taken is to protect forests and very quickly reduce greenhouse gas emissions.

Mike, that tees you up nicely. But of course, stopping deforestation in the tropics is not as simple as just putting an edict out there to stop deforestation. There are people who live there who need to produce food and make a living. And this is, you're right in the mix figuring out how do we stop deforestation while also enabling well being and sustainable development. So what are some of the mechanisms and opportunities there?

Yeah, so that, getting to Sue's point, it's absolutely right. When you look at tropical forests, we have to. First of all, photosynthesis is the only thing taking CO2 out of the atmosphere right now. Right. So we have to protect that. So to protect the forest, we have to end fires. And that getting to Heather's point then is we have to find ways for agriculture to continue, whether that's small household agriculture or some of the larger agriculture, much larger scale stuff that's occurring without any new deforestation and with and, and reducing the degradation that's occurring. That means, again, eliminate fires from any part of the process. It means things like helping households, getting technical support to households so that they can better grow crops on their land. You know, these, many of these households are just growing for themselves and a tiny bit for the market. So, you know, and it's, it turns out that a little bit of technical support to families goes a long way in improving, well being through improving crop production and their access to markets. So we have to, it's really what has to be done is we have to be working with the individuals. There has to be outreach to do that. And then there's also just, you know, some of the largest. There's a lot of illegal deforestation that takes place that has to be gotten under control. And that's more of a federal and state level. That can be challenging in some, it can be very challenging if, if, if there's not the political will to do it.

So, Sarah, last but certainly not least.

Yeah.

How do you think about what it is we need to do and what the opportunities or mechanisms we have available to, to get it done? Sure.

I mean It's a daunting problem. And I think that causes a lot of people to fear that there's nothing they can do or that the problem is too big or that we've already lost the point of return. I think if you take anything away from today, hopefully it's that everything we do now, whether it's reducing emissions, reducing deforestation, or adaptation, everything is going to help because the faster we go down these stairs, the harder the problem is. But we're taking it step by step so we can slow down and we can prevent ourselves from going over one more step. When it comes to things like sea level rise and the loss of ice, while there's a certain amount baked in, none of the kind of collapse or tipping points that we're talking about really should worry people in terms of the next decades, but they should still be worried because the sea level rise that we're experiencing now has nothing to do with passing these instability points. It's entirely this nonlinear response to warming of the atmosphere in the ocean. So the more quickly that we can reduce emissions and slow warming and get back on these lower target scenarios, the better we're going to be. But at the same time, we have to really help communities that are already experiencing. This is something that's happening right now. Communities are being flooded in the US around the world. There's displaced people, there's climate emergencies already happening. So we can't also just worry about. We also need to help communities, especially communities have been affected or under resourced communities, to prepare perhaps to retreat. We have to be prepared to move inland. We have to help make that more equitable. So I think we need to be doing both those things in parallel.

Well, it is 3:59. We have raced through this hour. I want to thank all three of you for a fabulous conversation. I want to thank everyone who joined us and for all of your dozens and dozens of fabulous questions and comments and one theme that we haven't addressed a whole lot yet. But I want to just quickly, in our last moment here, is what do I do with this information? How do I share this? How do I talk about this? And will these presentations be available so quickly to answer some of those questions? This whole conversation has been recorded. That recording will be available. We will email it to all of you next week. It will be on our website, woodwellclimate.org and also on our YouTube channel. So one easy thing you can do is simply share that video with those that you would like to communicate about this with. Hopefully we've also offered you an alternative framing besides this single tipping point, end point of no return with the acceleration down the stairwell today and some thoughts about the work that is going on to try to stop our acceleration down that staircase. So again, thank you so much to all of our panelists. We hope you will all join us back here same time Wednesday, two weeks from now for our next in this series, which takes that next step and starts to delve into what Mike was getting at in terms of photosynthesis being the best tool we have right now for pulling carbon dioxide out of the atmosphere, looking at the global potential of natural systems and also the technologies that are in development for pulling carbon dioxide back out of the atmosphere as some of the solutions and opportunities that we have available to us. So please join us there and I will, as we close down here, put a link up for you to find our website and subscribe to our newsletter to learn more about those events and learn more information that you can continue sharing with your communities. So thank you again everyone and enjoy the rest of your day.