2Celsius
"A podcast 2 degrees Celsius hotter" (2C) is a Brussels-based enterprise that brings about hot dialogues about everything climate. The episodes are made and edited by Francesca Fazey and Raul Cazan while the whole product is supported by Association 2Celsius (2Celsius.org).
2Celsius
METHANE. Unravelling nature’s methane: The threat of methane climate feedbacks
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Host:
The show is presented by: Francesca Fazey
Affiliation:
The show is brought to you by: 2Celsius Association
Resource List:
1. Environmental Investigation Agency (EIA)
2. International Methane Emissions Observatory (IMEO)
3. International Energy Agency (IEA)
5. United Nations Global Methane Pledge
6. Rocky Mountain Institute Climate Program
7. Oxford Institute for Energy Studies
9. Greenhouse Gas Laboratory, University of Royal Holloway
10. Romanian Methane Emissions from Oil and Gas
Laboratory of Climate and Environmental Sciences, Paris
11. University of Alaska Fairbanks, Fairbanks, USA
12. NASA Goddard Space Flight Centre, Washington DC, USA
Contributors:
Raul Cazan, Founder of The 2Celsius Association, Bucharest, Romania
Kim O’Dowd, Campaigner at The Environmental Investigation Agency, London, UK
Dr Roland Kupers, Global Advisor to the United Nations Environment Programme’s International Methane Emissions Observatory, Amsterdam, The Netherlands
Deborah Gordon, Senior Fellow, Watson Institute for International and Public Affairs, Brown University; Senior Principal at the Rocky Mountain Institute (RMI) Climate Program, Washington DC, USA
Dr Philippe Ciais, Associate Director, Institut Pierre-Simon Laplace (IPSL), Paris, France
Théophile Humann-Guilleminot, Campaign Manager, Clean Air Task Force ,Athens Greece
Dr Dave Lowry, Reader: Stable Isotope and Greenhouse Gas, Department of Earth Sciences, University of Royal Holloway, London UK
Dr Rebecca Fisher: Reader: Atmospheric Methane, Department of Earth Sciences, University of Royal Holloway, London UK
Dr Thoman Roeckmann, Professor of Atmospheric Physics and Chemistry, Utrecht University, The Netherlands
Professor Jonathan Stern, Distinguished Research Fellow, The Oxford Institute for Energy Studies, Oxford, UK
Melanie Kenderdine, Principal, Energy Futures Initiative, Washington DC, USA
So far in the podcast, we've focused almost entirely on methane from human sources. But these are only half the story.
SPEAKER_00The other half of methane that's emitted to the atmosphere is coming from natural processes that include wetlands, lakes, rivers, and ponds. Also, termites play a fairly significant role in producing methane. There's also some methane that's produced from the incomplete combustion related to wildfires. And then there's other smaller natural sources of methane that come from things like geologic seepage from volcanic activity.
SPEAKER_04These would all be fascinating to talk about. Termites, especially, right? But we're going to concentrate on wetland methane emissions because they're the biggest source of natural methane, around 60 to 70%. And because they may also be hiding a few potential traps for us in terms of our policy efforts to bring atmospheric methane down. These traps are known as climate methane feedbacks.
SPEAKER_02When we let our models calculate wetland emissions, we see that climate change alone is producing an intensification of emissions.
SPEAKER_04If you're joining us for the first time, this is Methane, a podcast about the world's second most important greenhouse gas and potentially our only opportunity to cut global warming within our lifetimes. The show is brought to you by the 2Celsius Association, and I'm your host, Francesca Faze. As climate change raises global temperatures and changes rainfall patterns, one of the more worrying possibilities that scientists and policymakers must grapple with is the threat of feedback loops, a triggering of extra greenhouse gas release that then further adds to the heating process. And while carbon dioxide presents feedback threats too, methane feedbacks, especially from natural sources like wetlands, are particularly concerning. You may remember Dr. Philippe Siez from episode two. He studies the atmospheric sources and sinks of carbon dioxide and methane at the Laboratory of Climate and Environmental Sciences in Paris. Now to focus a little bit more on natural methane emissions and specifically wetlands, can you explain what is wetland methane feedback?
SPEAKER_02Well, the idea is that methane is produced at the bottom of wetlands which are permanently flooded system because of those famous bacterias that, you know, like low oxygen environment.
SPEAKER_04Now if you joined us for our earlier episode on where methane comes from, that's episode two. This might sound familiar. If you remember, methane can be thermogenic, as in the main ingredient of natural gas, but it can also be biogenic, formed by certain bacteria that can survive in environments that have no oxygen.
SPEAKER_02These bacterial reactions are favored when you have more inundation, more water, means generally more methane production, and also when the climate is warmer, because like for all microbial reactions, at 15 degrees they will produce less things than at 20 degrees. So when you have both warming and wetting, means more water, over a wetland, it will tend to increase its methane emissions. And what we call the methane feedback is that if climate change is resorting into wetter and warmer conditions over the place where you have wetlands on Earth, it will increase the methane emission from those wetlands and it will further feed to the warming, and more warming will again increase the temperature and the hydrological cycle that may further increase the wetland methane emissions. That's why we call it a feedback. It's an amplifying feedback on climate change.
SPEAKER_04You may think you're not familiar with methane feedbacks, but there's at least one that I'll bet you've probably heard of already. The hypothesis of a mass methane feedback from thawing permafrost has captured the attention of both scientists and the public for decades now. The idea is compelling. The permafrost is like the Earth's freezer, with tens of thousands of years' worth of dead organic matter preserved and locked in the frozen soils. As climate change warms these regions, that freezer thaws, paving the way for thousands of tons of methane that we haven't accounted for to be released. At small scale, scientists like Professor Katie Walter Anthony at the University of Alaska Fairbanks have already started to show that lakes that are forming above the frozen ground in the permafrost regions are riddled with methane bubbles that can be ignited as they escape. Here she is with a few fellow researchers making a video for the university a few years ago.
SPEAKER_01Methane is formed in millions of lakes around the Arctic where permafrost is coming. And each year these lakes are emitting already tremendous amounts of methane. But when we look at how much carbon is in permafrost still frozen, and the potential for that permafrost can come in the future, we estimate that more than 10 times the amount of methane that's right now in the atmosphere will come out of these lakes.
SPEAKER_04This potential for a mass methane release from warming permafrost is the main methane feedback that scientists have been watching. One of those scientists who studies methane feedbacks and interactions between ecosystems and the climate is Dr. Ben Poulter.
SPEAKER_00My name is Ben Poulter. I'm a research scientist at the NASA Goddard Space Flight Center in the Earth Sciences Division, which is located just outside of Washington, DC. And my research team and I focus on trying to understand the role of terrestrial ecosystems in the global carbon cycle.
SPEAKER_04And as it turned out, he was pretty familiar with Philippe Siez, too.
SPEAKER_00Philippe was my boss, like, I don't know, 15, 20 years ago. So yeah.
SPEAKER_04I started off asking Ben to explain just how these dramatic methane bubbles trapped under the ice formed.
SPEAKER_00Right. So about 20% of methane emissions come from high-latitude wetland ecosystems. And so this includes things like the tundra, the permafrost soils, as well as uh dozens to hundreds to thousands of very small lakes that are found throughout the boreal zone. And in the shoulder seasons, uh so in the fall or the autumn, as the soil is freezing, the surface waters freeze first. And then there's a there's a delay in when the uh the soil freezes up. And so methane is still the microbes are still active and they're still producing methane, but then there's a cap of frozen water above the water column. And so the methane bubbles aren't able to escape out into the atmosphere and then accumulate in in sort of these frozen capsules of gas within the frozen lake surfaces. And so uh colleagues at the University of Alaska and and elsewhere, uh Katie Walter Anthony has sort of shown with these really fairly dramatic videos that you can sort of crack the ice to release the methane that's trapped there and then set fire to it and sort of have these fairly impressive bursts of flames as that methane is combusted.
SPEAKER_04The formation of methane by microbes is kind of key to these natural feedbacks. We mentioned it earlier, but just to make sure you know how it works.
SPEAKER_00Methane is produced in environments where there's no oxygen. And so when you're in an environment that's uh flooded by water, that the oxygen is in very low concentrations, especially in stagnant water, and the microbes that are living in the soil and that are consuming carbon have a different chain of chemical reactions that result in methane being produced through the respiration process rather than carbon dioxide. And so uh wherever you find oxygen-deprived or anaerobic environments, you'll likely find methane being produced.
SPEAKER_04That's why wetlands are such a massive source of methane, around 30% of the global total. And if you think about it, thawing permafrost is essentially converting ground that is frozen solid into giant, slushy wetlands.
SPEAKER_00So permafrost is carbon that's frozen below ground. And so it's it's organic carbon that's that's accumulated over thousands or tens of tens of thousands of years. The concern is that as the permafrost thaws with climate change, that will increase the uh amount of microbial activity, where those microbes will then be more active during the year or for the duration of the year because the seasons will are changing. And that carbon will then be converted to either carbon dioxide through aerobic respiration when you have oxygen, or the carbon will be converted to methane through anaerobic respiration by the microbes.
SPEAKER_04So the concern isn't that there's a kind of store of methane that's currently frozen and will be unlocked. What it is is a store of carbon that could then, if it's warm enough, be consumed and processed by microbial activity that currently it's too cold for there to be. Is that right?
SPEAKER_00Exactly. Yes. In the permafrost, that methane is stored sort of indirectly through the frozen organic carbon that's in the soil. And as the microbes start to decompose that carbon, the concern is then that the microbes will start producing methane or will start producing CO2. And the question is really about which pathway those microbes take in the future, because we're not sure whether in the future, as the permafrost thaws, that permafrost will be sort of released as carbon dioxide or released as methane.
SPEAKER_04And that will be a function of whether of how oxygenated or how aerobic or anaerobic those environments become.
SPEAKER_00Exactly.
SPEAKER_04The huge stores of carbon aren't the only potential source of methane in these chilly regions. There is frozen methane gas too, called methane clathrates or hydrates, which are methane molecules trapped inside special crystals of water in the ocean floor.
SPEAKER_00Just as a side note, there are frozen stores of methane as a gas, and these are the methane clathrates that are stored deep under the ocean in the Arctic. But there's lots of there's lots of uncertainties because the ocean is so deep, as those bubbles get away from the sediment to the surface, they have to pass through sort of oxygenated ocean waters, and the their chemical reaction with the dissolved oxygen in the water tends to convert that methane to carbon dioxide. So we're not we're not sure if we'll see these big sort of belches of methane coming out as the methane catharates thaw, or whether we'll see that methane be converted to carbon dioxide.
SPEAKER_04So with both of these potential sources of methane in the permafrost and localized studies on these lakes already demonstrating methane pressing up against the ice as the Arctic warms, are we seeing the beginning of this ticking time bomb from methane feedback in the permafrost?
SPEAKER_00I think there's a bit of a myth about the role that thawing permafrost will play in climate and methane feedbacks going forward. 20 or 30 years ago, a lot of the research on wetlands and methane was being carried out in the Arctic. And combined with the knowledge that was being gained on how much carbon is stored in the soils, so billions of tons of carbon being stored in the permafrost region made us as a scientific community sort of very aware and sensitive to the fact that we could be seeing this ticking time bomb as it's been referred to of methane releases. What's happened since that research was done a few decades ago is that the Arctic is warmed, I think four times the rate of global warming. And the measurement network that we have in the Arctic hasn't shown any increases in methane concentrations being abnormal to the global growth rate of atmospheric methane. And so we don't seem to have any direct evidence that there has been a uh a climate methane feedback triggered in the Arctic. We're seeing um these frozen soils start to change biogeochemically, but at the regional scale, we haven't seen any uh evidence that methane concentrations are increasing because of the thoring permafrost.
SPEAKER_04Why do you think that is? You know, on paper it sounds fairly straightforward. All the carbon, you know, temperature release, microbial activity, boom, boom, boom, two plus two is four. What do you think could be happening that would account for that?
SPEAKER_00It's either we don't have the right measurement network. I mean, there's there's only a handful of locations being measured in the Arctic to observe any sort of climate methane feedback. But then when we look at the climate methane feedback from a global perspective, we also don't really see evidence that the permafrost is emitting more methane than it was 10, 20, 30 years ago. You know, the the alternative hypothesis here is that the permafrost that is thawing dries out in the summertime and is being released as uh carbon dioxide. And so maybe we uh sort of misunderstood the thaw dynamics. Uh they're they're incredibly complex with um which layer of the permafrost is active versus inactive in the context of how much is thawing each year. There's a lot of sort of finer scale processes that make it challenging to generalize that the thawing of permafrost will create more methane concentrations.
SPEAKER_04That complexity at scale is something Philippe Siez referred to as well when I put the same question to him.
SPEAKER_02Arctic soils are very complex. They can become drier, they can become warmer. So at the landscape level, you have very big variations of the methane emission. That's the reason why it's so difficult to make any global estimate of this permafrost methane feedback. We know that the thermocast lakes are big sources of methane. There is absolutely no doubt about it. The question is: is it a small phenomenon that you observe at a particular site, or is it something big enough at the scale of the entire Arctic to become a new significant source? We know that the process happens at field scale, but we have no evidence for this process to have started over the entire Arctic over the last decade. It doesn't mean that it will not start maybe in the next two or three decades, but insofar we have not observed a massive increase of permafrost methane emissions in the recent years.
SPEAKER_04So is that it then? We're in the clear. Not quite. It might not be coming from permafrost, but when we let the computers crunch the numbers, a climate-driven increase in methane emissions does appear to be underway.
SPEAKER_02You know, it's very difficult in fact to measure the wetland emissions, so we have to estimate them with models. But when we use those models and when we let the models see the historical change of climate, there are some regions where there is more precipitation, like the Arctic and around the equator, some regions where there is less precipitation, like in the uh dry regions mainly. And there is, you know, warming everywhere, which is accelerating. When we let our models calculate wetland emissions, we see that climate change alone is producing an intensification of emissions.
SPEAKER_04The actual measurements of methane in the atmosphere also suggest that something weird is going on. While methane levels were growing steadily until around 2000, between 2000 and 2006, they stopped. So the levels were still high, but they weren't changing. In 2007, they started climbing again until 2020, when suddenly methane in the atmosphere went crazy, growing at double the previous rate. The same trend continued in 2021. And while it's tailed off a little in 2022 and 2023, it's still rising far faster than it used to be. But if not from the permafrost, then from where?
SPEAKER_03There's been a lot of research into what's caused this change and this stable period and then an increase in concentration since 2007.
SPEAKER_04Someone who's been heavily involved in trying to solve this puzzle is Dr. Rebecca Fisher from the University of Royal Holloway in London. Rebecca studies atmospheric methane, specifically looking at something called isotopes of methane, small chemical signatures that can help scientists distinguish between methane formed biologically and methane from oil and gas. If you've heard our previous episode, you'll recognize Rebecca and the background noise to our conversation from our methane hunting expedition in episode three.
SPEAKER_03The isotopes give us a big clue here, because this tells us about where the methane is coming from, and it looks like it's more biogenic sources, and much of the growth has been in tropics. Tropical wetlands are the biggest source of methane. So it looks like tropical wetlands recently emissions have increased.
SPEAKER_04So not the icy wetlands of the tundra and the Arctic, but tropical wetlands instead. What do scientists base this on? Well, a curious coincidence for one. In the same two years that the methane growth rate doubled, a few key tropical wetland complexes experienced particularly high temperature and rainfall as well, causing them to massively expand beyond their normal seasonal variations. Here's Philippe Sears again to explain. Wait, uh wetlands in North Africa?
SPEAKER_02Wetlands over North Africa doesn't seem to be very intuitive because you know we have the Sahara desert. But in fact, just south of it, there are very big inland rivers delta, like the Niger River, as a big kind of inland delta. It evaporates in the flatlands and it creates seasonally very large flooded areas. In the south of Sudan, also, there is a huge wetland complex which is formed by seasonal increase of precipitation during the wet season. And those North African wetlands seem to be particularly sensitive and important in explaining the recent growth of atmospheric methane.
SPEAKER_04And it isn't just models that are suggesting that these tropical wetland feedbacks are potentially a bigger and more immediate threat to climate change than we initially realized. Here's Ben Poulter again.
SPEAKER_00It was only within the last five years that we've really started to recognize the role that tropical wetlands on the African continent play in the global methane budget. I think 2019, some colleagues estimated the amount of methane being produced in the Sood wetlands in South Sudan. And they discovered using satellites to help understand the wetland methane emissions, that around I think five to 10 teragrams of methane are being produced in the Sood wetlands. And so this is this five to 10 teragrams is in the context of wetlands producing about 150 to 200 teragrams per year. So it's you know it's about 5 to 10% of the global wetland methane emission budget just being produced in this one isolated wetland complex in South Sudan.
SPEAKER_04So again, as we've mentioned before, we see the critical importance of technology in understanding the scale and complexity of methane emissions. Not just the human sources, but disentangling the natural ones as well. Can we or do we tie that to climate change and global warming, or is that a signature that is separate?
SPEAKER_03Now this is a really big and important question here. So if you have warmer, wetter wetlands, you'd expect more production of methane. And with a changing climate, in many parts we are getting warmer, wetter areas. So that would suggest that we get higher methane emissions from those areas.
SPEAKER_04You said that's a really important question in a way that suggested there was more to it than that as an obvious link.
SPEAKER_03I mean, when this methane growth first started, a lot of the focus was on the Arctic. Was it because the Arctic was getting warmer frost melts? But it looking at the geography of where the biggest emissions have happened is not just focused on the Arctic, it's not tropics. And then a lot of focus was on fossil fuel extraction, fracking, for example, in the US. And has that been a big extra source of methane? The timing was very similar to when methane started increasing. The gas um extraction increased significantly over this period. And we've also got a growing population, there's more people to feed, there's more agriculture, more agricultural emissions, more rice, more ruminants, cows and sheep. And we've got waste, more waste emissions. So all of these things add up. But it does seem like the wetlands have been a big part of it, which is perhaps surprising that it's not just those more man-made sources.
SPEAKER_04So not only are our own emissions of methane going up, the process of climate change itself is likely to trigger higher natural methane emissions too, which will feed back and cause further warming. And the process appears to have started already, not from the permafrost where we predicted, but from the northern tropics, which until five years ago we didn't even know were a major methane source. And not only that, but once these feedback loops have been triggered, there are no natural barriers to turn them off.
SPEAKER_02You have a process, bacterias, which is emitting uh emissions. It depends on temperature, and if you change the temperature, if you change the precipitation, nothing prevents emissions from increase. There is no strong limit to the amount of carbon that can be produced and released at methane in wetlands. There is a lot of carbon as a substrate for bacteria to eat. So the process is not going to be limited by the exhaustion of food for bacteria. It's only going to be limited by temperature and precipitation conditions.
SPEAKER_04What does this all mean from a policy perspective? It puts even more pressure on to curb the methane emissions that we can control. Closing gas leaks, even eating less meat, is a lot less complicated than trying to manage runaway methane from the world's wetlands. Here's Ben Poulter again.
SPEAKER_00The mitigation of methane from wetlands is incredibly complicated, sort of given the fact that wetlands provide us with all sorts of important benefits for biodiversity and for society. And so we obviously don't want to start destroying wetlands to drain them and to prevent them from producing methane. There are discussions about changing the chemical state of the soil so that the microbes uh don't produce as much methane or produce other trace gases, but there's probably other sorts of um unintended consequences that could come from that sort of uh manipulation. So I think at the moment it seems like expanding the monitoring of wetland methane emissions are really the priority. And then helping inform the policymakers that are responsible for establishing the nationally determined contributions to include climate methane feedbacks as they go forward in the in the various global stock takes is really critical.
SPEAKER_04And why do you think it's important for policymakers to take this into account?
SPEAKER_00If climate change is now causing wetlands to emit more methane, then there's potential for wetlands to derail efforts like the global methane pledge to mitigate atmospheric methane and to help us reach net zero emissions by mid-century without exceeding one and a half or two degrees warming. So looking at methane capture and methane mitigation options is, I think, a really important part of the portfolio of society aiming to stay below 1.5 degrees if we haven't exceeded it already, and definitely two degrees warming.
SPEAKER_04And finally, Rebecca Fisher again. Does it change our understanding of the importance of various sources? Does it make us think maybe some of the biogenic or the natural sources are more important than oil and gas, say?
SPEAKER_03There's not much we can do about a wetland other than reducing our overall warming of the planet. So it kind of makes it more important that we reduce the emissions we can do something about.
SPEAKER_04You've been listening to Methane, a podcast about the world's second most important greenhouse gas. With me, Francesca Fazy. Next up, we go back to methane and energy. Should what we know about methane's climate impact change how we view the role of natural gas in our future energy systems.