As Gabriel says in the interview, if the AMOC collapses then we can expect much harsher weather in Europe (especially in UK & Ireland) as less heat is transported via the Atlantic circulation. Less heat means less moisture leading to less rain and more drought. In these conditions, food production is impossible and, with concurrent food crashes around the globe, famine is likely. What an AMOC collapse means for us all should be understood by citizens and policymakers alike. Averting it, if possible, a primary collective goal.
Prof. Diana Urge-Vorsatz (IPCC): In the last two, three years there were at least five papers which warned us that the probability of the AMOC collapsing is bigger than we anticipated earlier and it may actually be happening sooner. With respect to IPCC consensus, what’s your take on the level of the scientific consensus on this?
Prof. Stefan Rahmstorf (PIK): Yes, there is pretty large consensus that the AMOC has a tipping point that has been confirmed by every model where this has been properly examined. There is maybe not a full consensus such as in the IPCC but very likely agreement that the AMOC has been slowing down in the last decades.
There’s another paper coming out next week which will confirm that once again and I would say there is a consensus that there is a big uncertainty of where exactly that tipping point is and whether we will cross it. That is uncertain and you mentioned these so-called early warning signal studies that have pointed that it’s much closer and maybe already in the next few decades we might pass that tipping point where we set the AMOC on a path of shutting down over then the following 50 years or so. But these studies have a lot of uncertainty and in my review article that I wrote earlier this year I argued that we’ll never get a certain warning.
I don’t think with the data we have from the past etc we can give a clear very robust timing of when this tipping point will be crossed but I don’t think we necessarily need to because the conclusion is that there is a really significant risk or high risk as the IPCC says beyond 1.5 degrees and that should be a very powerful reason to get out of fossil fuels as fast as we possibly can.
Prof. Diana Urge-Vorsatz (IPCC): Thank you Stefan and sorry for coming back but even in the most recent science paper on tipping points, the AMOC is not even at the beginning of the scale of the different tipping points and I think the medium probability for the AMOC it was about four degrees and we are pretty far from four degrees yet. As decision makers, we are a bit confused by the contradiction between these otherwise very high tipping levels versus these recent studies.
Prof. Stefan Rahmstorf (PIK): Recently I think the evidence has shifted towards an earlier tipping point so certainly my assessment has changed. I used to agree that it’s probably less than 10 percent within this century and now I would see it more like 50-50 that we will pass the tipping point in this century because of all the recent evidence that has come in and that hasn’t maybe filtered through to all review efforts but I think it’s also not so important in a way because even a 10 percent risk is too high given the consequences.
So, it’s like, if you go and board the plane on the way home after the meeting in Baku and they tell you, ‘well the risk of your plane crashing is less than 10 percent’, would that be reassuring? I personally wouldn’t get on such a plane and it doesn’t really politically matter whether the risk is 10 percent or 30 or 50%. it is too high and we need to get out of fossil fuels to minimise that.
From Climate Genn host Nick Breeze:
Welcome to this ClimateGenn Episode. That opening clip was recorded on the Cryosphere Pavilion at COP29 in Baku. It shows IPCC Deputy Chair, Diana Urge-Vorsatz asking Professor Stefan Rahmsdorf about the latest research on the potential halting of the Atlantic Meridional Overturning Circulation – known as AMOC – the ocean currents that transport heat from the tropics to the north Atlantic.
In this following interview with researcher Gabriel Pontes, we expand on his recent AMOC research and what this means for places like the UK and Ireland, identifying key components of the AMOC puzzle. We also consider whether policymakers should be weighing this kind of climate risk more seriously.
If you are interested in how the COPs have been manipulated and rendered unfit for purpose by successive governments then you can order my book ‘COPOUT’ from any online retailer. COPOUT traces my own footsteps documenting the failures that have led us to where we are now in the era of severe consequences.
In the next episode I speak with Camilla Gjerde about her recently published book, Natural Trailblazers, about the authors travels in search of .
Throughout 2025 I will be exploring a number of climate related themes that intersect with ecology, politics, engineering, restoration, and generally clinging on for dear live in this era of manmade madness.
Please do subscribe to get additional and early content.
Thank you.
Interview with Gabriel Pontes on new research into the collapse of Atlantic Meridional Overturning Circulation
[Nick Breeze]
So Gabriel, thank you very much for taking the time to speak to me and we’re going to talk about your recent research and from the outset the Atlantic Meridional Overturning Circulation or the AMOC has become very famous in recent years. Can you start by giving us a brief definition of what it is and how it fits into the global climate system?
[Gabriel Pontes]
Hello Nick, first I’d like to thank you for the invitation to talk here about this very important oceanic circulation that has, as you mentioned, has gained a lot of attention due to its importance in the transfer of heat across the global oceans. So if I could define, quickly define the AMOC, I would say that this is the most important ocean circulation that transports heat across the oceans and does affect the Earth’s energy balance.
[Nick Breeze]
Okay and just to give it some context, what’s the impact of the AMOC on somewhere like Great Britain and Ireland?
[Gabriel Pontes]
So given that this vast current transports a huge amount of heat towards the north, so what we’ve got is that the north, the hemisphere of the globe, is slightly warmer than the south. So that’s what we expect when we are talking about regions around Europe or around the southeast and Atlantic region, sorry about northeast and Atlantic region, where most of this heat is delivered, warming up the surface. So this creates mild temperatures around Europe.
[Nick Breeze]
Okay and in those milder temperatures, the same sort of latitude around say Canada, it’s different isn’t it? Because they didn’t have such a warming mechanism.
[Gabriel Pontes]
Yeah, so that’s a big difference. If you take like two latitudes, one close to Europe and one closer to North America, you’re gonna see that the temperatures in Europe are way warmer than the ones that we expect in Canada. And that’s because those currents, they transport the heat from the tropical Atlantic, they pass through the coast of the US, but afterwards they diverge and head into Europe, where they carry most of this heat, and most of this heat is then released into the atmosphere around Europe.
[Nick Breeze]
Okay and obviously that’s how we’ve built our sort of civilisation, our food systems, agriculture, winemaking, all this kind of stuff in Europe. It’s kind of dependent on this conveyor of heat from the southern region.
[Gabriel Pontes]
Yes, that’s true. So if we take, for example, how our civilisation or how humanity has migrated in the past, we are going to see that these migrations, those tracks of migrations, they were basically determined by the climate patterns that were most important at each one of those periods in the past.
[Nick Breeze]
Okay and when we talk about the AMOC in the current context, the reason it’s getting so famous is because scientists are worried about how it’s slowing down and the potential for shutting down. Monitoring the Atlantic circulation closely only started about 20 years ago. What has been the difference between the climate modelling assessments of the AMOC and the observational assessments, and how has your research kind of looked at that difference?
[Gabriel Pontes]
That’s true. There was just like, that has been just 20 years that we are effectively monitoring those currents. And before that, we rely on some sparse data that we’ve got previous to the satellite era, because then the satellite era could allow us to to have some vast observations around the surface of the globe.
But just before that, we relied on some sparse observations given by ships, or some point measurements across the global oceans. And that’s what makes it difficult to assess how the climate has been changing before the satellite era, before around the 1980s. And that’s where the climate models kick in, because then with climate models, we can simulate any climate.
So in this way, we can just apply what we thought that we were the most important drivers of the climate at the time previous to the satellite era, and then evaluate how the climate was. And if the models actually simulate what we expect, what we see in this data. And that’s the importance of this research, because in this research, we reconcile both the observations and the climate models.
And now, we can show that both are pointing towards the weakening of this important circulation system.
[Nick Breeze]
Okay. And with this weakening, what are the key characteristics? Because I know that the Arctic is warming much faster than everywhere else.
And then one thing we saw at the COP, there when Stefan Ramsdorff’s presentation was played, and he did a Q&A afterwards, was this cold blob, I think you referred to it as the warming hole in the North Atlantic. How does all of this fit into the jigsaw puzzle? Can you explain?
[Gabriel Pontes]
So, for example, this warming hole that Stefan Ramsdorff has referred to, is basically the main fingerprint of the weakening of the circulation, because it’s located exactly where this extra heat from the ocean is delivered to the atmosphere. So this warming hole means that this heat is not being anymore delivered to the atmosphere. So it’s creating cold conditions around the area, and thus decreasing the surface temperature.
So that’s the main fingerprint, and that’s one of the fingerprints of the circulation that has been extensively evaluated in the past. But our study also shows that there are other fingerprints across the global oceans that can also be used to infer what has been going on with the circulation. And in our study, we use the South Atlantic in addition to the warming hole that has been described earlier, we use the South Atlantic as some key regions where concentrated some of the hotspots.
So this means that the heat that was supposed to be heading northwards towards the North Atlantic, it’s now being concentrated in some key regions of the South Atlantic. And these allow us to provide a more robust mechanism of the evidences that the EMOC has been weakening since the mid 20th century.
[Nick Breeze]
Okay, good. So if these hotspots are still in the south, how is this how is this playing out? I mean, you can see that it’s slowing down.
But is it, are we already starting to feel impacts from it?
[Gabriel Pontes]
Yes, yes, we are. Because, for example, there has been some quite a few years of intense warming along the East, along the West African coast, just southeastern in the South Atlantic. And this has been very famous.
And people have been describing those as the Big El Ninos, which are just some comparison with the Big El Nino that occurs in the Pacific. And given that this is also related to a key hotspot due to reduced, let’s say, how can I say, just reduced upwelling of cold waters that come from below of the ocean. And this mechanism just stops those cold waters from coming from below of the ocean, similar to what happens to the El Nino in the Pacific.
And so this could be probably being affected by this change in the oceanic circulation. And another hotspot lies on the on the South American coast, just by southeastern Brazil, where we’ve got another very important current that has been seeing some increasing temperatures in the past few years.
[Nick Breeze]
Is there a, for that last hotspot you mentioned, what’s the impact of that heating up? Does it have a direct impact on the surrounding area?
[Gabriel Pontes]
Yes, so the first impact is the increasing temperatures of the land. And as more heat is being released from the ocean to the atmosphere, it also enhances precipitation. So we’ve got some more precipitation extremes around those regions, and also causing huge damage for those densely populated areas.
[Nick Breeze]
Okay, so it’s a feeder of those storms. Can I just ask you, you mentioned in the paper that one of the feed-ins is the meltwater from Greenland and Canadian glaciers. And obviously, these are direct knock-on effects from all of our continual burning of fossil fuels and so on.
How relevant and significant are those factors?
[Gabriel Pontes]
So in our research, we just found out that, in fact, the effect of the meltwater that runs out from Greenland and from Canadian glaciers from those parts in the Northern Hemisphere, they have been, in fact, very important for the reduced oceanic circulation. And that’s why the previous simulations, the previous projects of the IPCC, they were not able to capture this reduced circulation in the ocean, because they were not taking into account the process or the effect of the meltwater. And that’s because of two things.
One of the things is that, far back in the past, we do not have measurements of meltwater. We don’t know exactly about how much the ice sheets were melting during that time in the 20th century. And the second fact is that this is quite difficult to be implemented.
And now our research shows that, in fact, 60% of the weakening of the circulation can be attributed to the melting ice sheets.
[Nick Breeze]
Wow. Okay. And I suppose one of the big questions that everyone’s going to be asking is, firstly, let’s start with what would be the impact?
So let’s take Europe, for example, if the AMOC shuts down, what can we expect?
[Gabriel Pontes]
So there are two things. Given that there will be less heat being delivered around Europe, we then expect, especially during the winter, so we expect that Europe is going to face some harsher winters. And in addition to that, given also that less heat is being transferred to the atmosphere, we’ve got less source of moisture.
So the water evaporates less than it would have evaporated if there were more heat. And so another thing that we can expect is some more intense droughts around Europe.
[Nick Breeze]
Okay, good. And what’s the level of certainty or probability that this is likely to happen?
[Gabriel Pontes]
Okay, that’s quite difficult for me to say. I would say that this would be the $1 million question, because that’s a highly unpredictable system. And the main thing is that we are trying to better understand all of the characteristics of the circulation and all of the dynamics of the circulations as the changes are going due to climate warming, due to global warming.
That’s what most of the scientists have been trying to address. How likely is this system to collapse within the century? And when we can expect this to collapse?
So from our research, our study, our model does not simulate a collapse before the end of the century. But there are two caveats here that I should mention. The first one is that we consider a kind of an optimistic scenario where we just project that the meltwater that runs into the ocean, it’s going to run into a constant rate.
And that’s not exactly how it occurs in reality. In reality, where we’ve got some pulses of meltwater, for example, when some part of the reaches some kind of a threshold, we can see those huge blocks of ice running into the ocean. And depending on how big or how large those ice blocks are, they can have a significant impact over the oceanic circulation during a short period of time.
So that’s what makes the predictability of the system so difficult for us.
[Nick Breeze]
Okay. And in previous interviews with people working on Greenland, for example, they’ve said that, you know, if we reduce emissions, fossil fuel emissions, then we would reduce the speed of the melt of the Greenland ice sheet. And what you’re saying is that if we reduce the speed of the melting of the Greenland ice sheet, for example, this could sort of help that more optimistic scenario that you’re talking about.
Is that fair?
[Gabriel Pontes]
Yes, I think that’s exactly what we try to address. So the more we reduce emissions, the more time we gain to effectively understand the system and better predict what’s going to happen. On the other way around, if we just do not stop our emissions as soon as possible, then we won’t have the necessary time to understand the system and the system can collapse before we actually know what is going on.
That’s quite difficult. And that’s what we are all trying to work on at the moment.
[Nick Breeze]
Okay. And given that that is an optimistic scenario and the emissions are still historically high, I mean, I spoke to people at the COP last week who are from fossil fuel producing companies who are not even thinking about stopping to produce fossil fuels and probably wanting to increase production. Does this mean that we have to really start considering the less optimistic scenarios and also try to better understand more socially what the impacts of this really mean?
[Gabriel Pontes]
So answering your first question, yes, it does. So if we should start to consider those less optimistic scenarios, especially because our research also shows that in fact, it seems that the ocean circulation and the climate system is more sensible to those freshwater fluxes, to those meltwater fluxes from the melting ice sheet than we thought previously, than this study. So this study is also showing that we only need some kind of a small amount of freshwater, meltwater that runs into the ocean in order to start to affect the system.
So the more we understand those processes, we are seeing that the climate is becoming less predictable due to those possible thresholds that could be crossed within this century. And regarding to the social impacts, what we expect are just unpredictable change in precipitation, where some regions can suffer of more prolonged pronounced droughts and other regions can suffer with extreme precipitation. And those changes in precipitations are not expected from the previous IPCC reports, because the previous IPCC reports are not taking into account that the system can in fact collapse before the end of the century.
[Nick Breeze]
Okay, and there is a problem when we talk about the IPCC reports is that they’re part of a much broader cycle themselves. So trying to get work like this, which has a sense of urgency about it, because the policies need to be enacted today, and not on a seven year cycle, whatever it is. We need to be much more dynamic in how we respond to this.
Have you had any interaction with policymakers whatsoever on this issue?
[Gabriel Pontes]
Well, the opportunity to talk to them. So I’d like to, because this is an issue that has to be tracked as the new research goes out, because every new step that we understand about this climate system is going to provide us some novel evidence or some novel directions from where the climate system is going to. And this will be an important information to update the policymakers in their decisions, in how to try to mitigate and adapt due to those different changes that have been, that are projected to occur.
[Nick Breeze]
Do you foresee a scenario where adaptation to a shutdown, a mock, is viable for places like in the UK, Ireland, Holland, or Scandinavia?
[Gabriel Pontes]
Well, I think that definitely those places, they should have at least this possible scenario as a plan B at the moment. So those places, they should definitely start to think about what are the main impact in those regions, because those are going to be regions that are going to be highly impacted. So what would be the main impact in those regions, and how they can mitigate that.
Because once the system starts to collapse, it could be very fast, and it’s going to reduce the time for mitigation and adaption.
[Nick Breeze]
When you say very fast, are you thinking decadal? Are you thinking one year, two years, or over a century? What’s your definition of very fast?
[Gabriel Pontes]
Yeah, so we are talking about decades. Okay, so at least one or two decades for for us to actually feel the more extreme consequences.
[Nick Breeze]
Okay, and it seems to dwarf our sort of petty political discussions that we’re having more widely at the moment. And what’s the next phase of research for you in this kind of area in your climate work?
[Gabriel Pontes]
So we are still trying to impact and trying to gain some more understanding of the system in order to better project it. So this was basically the first study that included the effect of meltwater and could represent the current state of the oceanic circulation. But there are many other processes that we don’t know at the moment, but they can help us predict the system.
So what we are trying to do at the moment is to address or trying to better understand those processes and then apply those processes back to the models and provide even more accurate projections of the climate system, not only of the oceanic circulation, but also what would be the impacts of the oceanic circulation in the climate system.
[Nick Breeze]
Well, okay, we look forward to seeing more of your work as it becomes available. Thank you very much for taking the time to speak to me.
[Gabriel Pontes]
