Episode description

In this episode, I talk with Sarah Smith of the Clean Air Task Force about methane, the greenhouse gas that falls out of the atmosphere more quickly than carbon dioxide but trap a lot more heat while it’s there. We discuss sources of methane pollution, opportunities for reduction, and recent policy developments.

Full transcript of Volts podcast featuring Sarah Smith, September 29, 2021

(PDF version)

David Roberts:

Methane is having a moment.

Methane — chemical name CH4 — is a fuel. It is the primary ingredient in natural gas, which generates about 40 percent of US electricity and heats about half of US homes. It is also an air pollutant, a precursor to ground-level ozone, which is toxic to humans. And it is also a greenhouse gas, much shorter lived in the atmosphere than CO2, but much more potent while it is there.

Methane in the atmosphere comes from leaks along oil and gas infrastructure, from agriculture (primarily cow burps and manure), and from landfills. Rising concern over methane pollution has culminated in the Global Methane Pledge, announced by President Joe Biden’s White House last week, which would have participating countries (which include the EU, the UK, and Mexico) reduce methane emissions at least 30 percent by 2030.

This followed the United Nations Environment Program’s Global Methane Assessment in May, which found that substantially and rapidly reducing methane is the only way to meet the international goal of keeping warming under 1.5°C.

Clearly, for those of us who haven’t been paying as close attention as we should, it’s time to tune into the methane debate.

The Clean Air Task Force has been tracking methane pollution and advocating for reductions for years. So I was eager to talk to Sarah Smith, the head of CATF’s Super Pollutants program, about the basics of methane: where it comes from, how it can be reduced, and the battles over it in US methane policy. (See also: Smith’s op-ed in Canary.)

Without further ado, Sarah Smith, welcome to Volts. Thanks for coming.

Sarah Smith:   

Thank you so much for having me, David.

David Roberts:   

For those of us who have not been tracking the details of methane as closely as they might: what exactly is methane? 

Sarah Smith:   

Methane is an invisible, odorless gas that is commonly known as the main constituent of natural gas. It has flown under the radar for far too long. It's currently contributing to about half the warming that we're experiencing today.

David Roberts: 

Methane is a greenhouse gas that traps more heat in the atmosphere than CO2, but for a shorter period of time. What is the climate change potential of methane, and how does it differ from CO2?

Sarah Smith:  

Every pound of methane heats the climate more than 80 times as much as a pound of CO2. But methane only lasts for about a decade in the atmosphere, which is a big opportunity, because quickly reducing the amount of methane in the atmosphere would very quickly slow warming, whereas carbon dioxide is slowly building up over time and takes much longer to reduce.

David Roberts: 

I’ve seen it compared to stock vs. flow. With CO2, if you stock it up in the atmosphere it stays, so you have to worry about the total amount. Methane is a flow problem; it's constantly coming out of the atmosphere. Is it fair to say that if we reduced the addition of methane into the atmosphere to the rate at which it was coming out of the atmosphere, we would basically stabilize its temperature effect? In other words, theoretically, there is some level of methane emissions at which you're not making things warmer.

Sarah Smith:

Exactly, and that's the goal: to get back to those pre-industrial concentrations of methane by ensuring that less methane is being added than removed.

David Roberts: 

It is startling that methane has caused half of historical climate warming thus far. How was that discovered, and how did we not know it for so long?

Sarah Smith:

I ask myself that question all the time. The latest report from the Intergovernmental Panel on Climate Change finally shone a bright light on methane; you saw the CO2 bar next to the methane bar and clearly, methane was causing a substantial amount of the warming, about half as much as CO2. Subsequently, the attention is growing, as it should, and as it has been for years, but finally, we're really reaching a crescendo here.

David Roberts:

What are the implications for policy? What does this allow us to do if we grab hold of the methane lever?

Sarah Smith:   

A powerful lever it is. We don't have a lot of time left — perhaps 10 to 15 years, maybe less — to bend the warming curve in order to stave off irreversible changes to our climate, including self-reinforcing feedbacks where the world warms itself, like the loss of the remaining reflective sea ice, which would add the equivalent of a trillion tons of CO2 to what's already been added.

There's also the Amazon tipping point, where the Amazon could be canceled out as a carbon sink. And many others. So we're in this race now to slow warming, and the biggest lever we can pull, by far, is cutting methane. We have the technology to quickly cut methane by at least 45 percent by 2030, and that would deliver an astonishing 0.3 degrees Celsius of reduced warming, along with a host of other benefits.

David Roberts: 

When you say reduced warming, you mean relative to baseline, right? 

Sarah Smith: 

Exactly. Bending the curve down, reducing the rate of warming. We could reduce this 0.3 degrees C by the early 2040s through reducing methane.

David Roberts:  

This is the key thing about methane. You could cut CO2 almost to zero tomorrow and the warming set in motion by the CO2 that's in the atmosphere would continue. Whereas cutting methane gives us this lever where we can promise visible results within a reasonable lifetime.

Sarah Smith:  

Decarbonization is critical for slowing long-term warming, but it doesn't provide any reduction in warming for 20 to 30 years, and we simply can't wait. We have to address methane.

David Roberts:  

Lately, there's been global attention to reducing aerosols and their negative environmental effects. But one of the things aerosols did, perversely, was thicken the atmosphere and shelter us from some warming. There's worry that reducing aerosols globally, while it will have immediate positive environmental effects on ozone, etc., will actually boost short-term warming. So this brings us back to the need to have a short-term tool to fight that effect.

Sarah Smith:   

That's an important insight and one that this latest report from the IPCC finally highlighted in clear terms.

David Roberts:   

Notoriously, there's been a big spike in methane emissions in the last few decades, and it's something of a mystery, as I understand it. Do we know where that methane is coming from? 

Sarah Smith:  

We're certain about the spike. But there is a lot of uncertainty around what's driving the spike.

David Roberts:    

Do we have a list of culprits? 

Sarah Smith:  

We think fossil is a significant part of the search, but probably not the only contributing factor.

David Roberts: 

In terms of knowing how much methane is in the atmosphere, we've historically relied on self-reporting by companies and countries that maybe can't be fully trusted to do transparent self-reporting. Now, we have satellites that can allegedly detect methane. What are the satellites revealing, and what will they reveal when there are more of them?

Sarah Smith: 

The satellite technology is improving, and it's exciting that several are planned for launch in the next few years. That will give us a much more detailed view from the sky of the emissions all around the world; in the case of the Carbon Mapper satellite constellation, near real-time data for the whole planet. That will revolutionize the policymaking landscape and industry, which will suddenly be on the hook to take this on.

David Roberts:  

Tell me a little bit more about the satellite network.

Sarah Smith:  

There's one called Carbon Mapper that will be a constellation, as I understand it, of more than 20 satellites, circling the globe, and providing data every few days. 

David Roberts: 

Is there a third-grade explanation of the science behind how, from space, you can detect a colorless odorless gas being emitted on the ground? 

Sarah Smith: 

Sadly, I'm not a satellite expert. But scientists in NASA's Jet Propulsion Lab have been involved in developing this technology, so I am confident in its ability to work.

David Roberts: 

It's like the entire world having a curtain pulled away: every single source of methane will be exposed. Do you have any guesses about what that's going to show? Are there going to be big surprises? What might we find out that we don't know?

Sarah Smith:  

Already, some of the satellites in the sky today — which aren’t as good as what's coming, but give us some early clues — have shown massive plumes of methane coming from oil and gas infrastructure, including pipelines, and have already resulted in some cleanup efforts. So I'm excited about the surprises, and hopeful the big sources will be caught more quickly.

What satellites won't be able to do is pinpoint every tiny leak, and we need to try to address those too. But satellites will be able to show us where the bigger emissions are coming from.

David Roberts:  

We keep hearing about giant methane deposits in the Siberian permafrost, in bogs and swamps. There's this constant worry about a tipping point that unleashes giant methane deposits from permafrost. What's the state of science on that? How worried should we be?

Sarah Smith:  

Right now, more than half of methane is coming from human-caused sources. We should address that as quickly as we possibly can, in part to help prevent a rise in methane from these “natural” sources, the leading one being wetlands. Right now, permafrost is not a huge source compared to others globally, but as temperature rises, it could bit by bit become a bigger source. But I don't think people should lose sleep over a one-day sudden surge.

David Roberts: 

You think the chances of a big dramatic release are relatively low?

Sarah Smith: 

Yes, that's what the science seems to be saying.

David Roberts:

I guess we can take some relief in that.

Sarah Smith: 

We still have a lot of work to do, but that's one bright spot.

David Roberts:

What are the biggest human-caused sources of methane emission, both globally and in the US?

Sarah Smith: 

Overall, they're fairly similar, with about a third of the emissions coming from the fossil sector, including oil and gas and coal mines; about a third, maybe a little bit more, coming from agriculture, with the main sources being livestock, manure, and rice cultivation; and then the final amount coming from waste, including landfills.

David Roberts:

I think we have a pretty good understanding of how methane builds up in coal mines and releases. But where in the oil and gas process are these leaks happening?

Sarah Smith:

The sad thing is that they're happening throughout the whole supply chain, from the well pad, where the gas or oil is being pumped out of the ground, where there are leaks; unloading of liquids along with gas from wells; pneumatic devices, compressors, storage tanks, dehydrators. All through the supply chain, many of these devices also exist: the pneumatics, the compressors, the tanks. Then, of course, you have the pipelines. All the way from the production through processing, transmission and storage, and even distribution portion of the industry.

David Roberts: 

So there's not one big spot to focus on; that's a little disheartening. Are there no junctures or concentrations we could target first, if we're trying to prioritize?

Sarah Smith:

You're pointing out a big reason why this emission problem still exists. It is dispersed. We are talking about millions of sources that can and must be cleaned up.

David Roberts: 

There has been a long ongoing argument in the climate world over the perennial question of how clean natural gas electricity is compared to coal electricity. Some say that there's so much leakage of methane in the supply chain before you get natural gas electricity that it wipes out any advantage natural gas has over coal; other estimates say no, the leakage rate is low enough that it still has an advantage. How confident are we that we know the leakage rate in this process?

Sarah Smith: 

The leakage of potent methane substantially erodes the climate benefit of gas over coal, and depending on where that gas is produced, how far it's transported, and how it’s transported, the upstream emissions can vary widely. All of that needs to be factored in.

But I think comparison to coal is letting us off too easy. It's not the ambitious benchmark that we need, which is near-zero methane emissions. Flaring needs to end, venting needs to end, these super-emitter plumes and leaks have to be found and fixed, and that antiquated equipment that vents methane to the atmosphere as part of its normal operation should be phased out.

David Roberts: 

Can you explain flaring and venting? When I tell people about flaring, they have trouble believing that I'm telling the truth. 

Sarah Smith:  

I experience that, too. It is remarkable that billions of dollars worth of gas gets lit on fire every year as a disposal mechanism. It turns out that burning it is better than just releasing it straight into the air, which is venting.

David Roberts: 

Natural gas is valuable, used in a lot of different ways, and we go out to mine it and search for it, but oil wells are throwing tons of it away. What's going on there? Why throw away a valuable resource?

Sarah Smith:   

The oil producers have not yet been forced to capture and utilize or sell the gas.

David Roberts: 

Couldn’t they make money? Why would they have to be forced if they could make money?

Sarah Smith:  

Certainly money could be made. The question is, could more money be made in other ways? That short-term profit is what they’re after.

David Roberts:

What would be involved in not venting or flaring, but capturing and transporting the gas? Is it additional infrastructure?

Sarah Smith: 

A lot of times it comes down to planning in advance and making sure that before the well is drilled, there's capacity to use or get rid of the gas. There are a wide range of solutions, from using the excess gas to make power on site, or making sure there’s a pipeline and a compressor there to get it to market. But companies aren't doing that without being required to.

David Roberts:   

Liquid natural gas is another big source of controversy. There are people advocating for liquid natural gas export terminals in the US; China is supposedly going to start importing a lot more liquid natural gas. Is liquid natural gas, in terms of the methane leakage in the process of making it, worse than normal natural gas?

Sarah Smith: 

There is energy that needs to be used to compress the gas into LNG and transport it. We're also concerned about emissions during that transportation process: boil-off of gas, leaks, even super-emitter events. We have an optical gas imaging camera that can be used to see the emissions that are normally invisible, and we've taken it to some LNG sites in Europe and seen the pollution. We know it exists, and we're concerned about it. It's an area where little study has been done so far, but all of these emissions do need to be factored in.

David Roberts:

The US fracking industry is likely to collapse soon, and there are thousands upon thousands of wells all over the place, many of which get abandoned because our laws about holding fossil fuel companies responsible for them are rather weak. Are they a source of methane? How big of a problem are abandoned wells? 

Sarah Smith:  

They are another source of methane, and we're especially worried about the ones where there is no longer a clear owner. Unfortunately, the government needs to step up with the resources and cap these pollution sources. Long term, we have to make sure that oil and gas companies are responsible for their wells.

David Roberts: 

What does that policy look like when they're responsible for their wells? Is it just a matter of bonding some extra money upfront?

Sarah Smith: 

I do think that's key, yes; making sure that enough money is actually bonded upfront that the well can be capped and properly maintained.

David Roberts: 

When we say capping a well, are we literally just talking about going and putting a cap on something? Is it just a concrete plug in a tube, or is there something more complicated involved?

Sarah Smith:  

Generally, this is plumbing, not rocket science, but it can be costly to properly plug these wells and then ensure that they're checked for leaks over time.

David Roberts: 

What's involved in stopping methane leaks in LNG production?

Sarah Smith: 

Step one, find the leaks: if it's with a camera, or a flyover, or, increasingly, satellite technology. Continuous monitoring sensors are also becoming more popular and lower cost. So detecting the emissions and then fixing the problem, which can be as simple as closing a hatch that's been left open, reigniting a flare that's been snuffed out, or fixing a hole in a pipeline or a tank.

David Roberts:  

It doesn't sound like it's a difficult technical problem or an intellectual challenge.

Sarah Smith:  

We have the technology today. In fact, the International Energy Agency says that half of the emissions could be cut from oil and gas at no cost, and 75 percent could be done at low cost with existing technologies. So there's a lot of potential here.

David Roberts: 

How can it be costless?

Sarah Smith:

In enough of the places, the pollutant is the product too. That’s how the minimal costs associated with finding and fixing these leaks and updating the equipment can be recouped.

David Roberts: 

The second big source of methane that you listed is agriculture. This is cow burps and cow poop? 

Sarah Smith: 

Those are two of the top ones, indeed.

David Roberts:  

What can be done about those?

Sarah Smith:  

On the cow burps, also known as enteric fermentation, there is no silver bullet, but there are solutions that should be pursued, including feed changes and selective breeding. Whenever we improve productivity and animal health and fertility, that's going to reduce methane emissions associated with the products from that animal. So those are good solutions. 

David Roberts: 

Breeding cows that burp less?

Sarah Smith: 

Selective breeding to improve productivity. This is an area that New Zealand has pioneered, and the reductions in emissions aren't staggering — they see a 10 percent reduction, often — but if we could extend that over more of the world, that would start to make a real impact.

David Roberts: 

What can be done with the poop? As I understand it, the poop right now goes into giant lagoons and sits there off-gassing. Is that right?

Sarah Smith:

A lot of that does occur, yes. Some farms have started to adopt these biogas digesters, which require maintenance but can be an important solution. And again, that gas can be utilized, so that's one solution.

David Roberts: 

Is that the main poop solution, capturing the gas and using it? Or are there other methods?

Sarah Smith: 

There are some other actions that can be taken, like decreasing the amount of time it’s stored before it's used, covering it better. There are some emerging technologies, like powdered additives that can be added to the slurry to reduce the emissions. But more study is needed to understand the effectiveness of some of these newer approaches, and more study should be undertaken, because the ag sector as a whole is a huge source of methane that we absolutely need to rein in.

David Roberts: 

A growing source, right, because more and more people are eating more and more meat?

Sarah Smith: 

That's right — projected to continue in that direction as well.

David Roberts:

It seems to me that one of the obvious solutions in agriculture is just to eat less meat and raise fewer animals. That would be the most straightforward way to reduce this, wouldn't it?

Sarah Smith:

That would certainly help. 

David Roberts:

It's funny that we have so much more faith in all the technological solutions than we do in the idea of persuading people to eat less meat.

Sarah Smith:

That's a challenging case to make, yes, even if it's in their own self-interest and would improve health.

David Roberts:

Is it safe to say that the reductions in agriculture are a bit more difficult, less thorough, and less fully understood than in oil and gas?

Sarah Smith:

Yes, that's true. There are steps that we could and should take today, but we won't get to zero overnight.

David Roberts:

The third big one, then, is waste and landfills. As I understand it, the reason they're off-gassing methane is that they contain a lot of organic material. Do we have any large-scale solutions for landfills?

Sarah Smith: 

No, unfortunately, not really. We could take a substantial bite out of the emissions through existing technologies, like header capping, capturing the gas from landfills and using it, or, if there's no way to use it, at least burning it off so that it doesn't vent directly to the atmosphere. As you said, the methane is a result of organic material decomposing in the landfill, so reducing the amount of organic waste that's winding up in landfills is also a important piece of the solution.

David Roberts: 

Which would be primarily food waste, right?

Sarah Smith: 

Right. Food waste is important to consider and important to try to reduce overall.

David Roberts:

Landfills are huge. What does it look like to capture the gas coming off of a landfill? 

Sarah Smith:

In order to capture the gas, the landfill has to be covered, and the gas essentially rises and gets captured at the centralized points. 

David Roberts: 

So that costs more. For your average landfill, can you make enough off the gas to pay for the process of capturing it? What are the economics there?

Sarah Smith:

The upfront cost can be a barrier. That's where we need to scale up financing and make sure that municipalities and government jurisdictions that are charged with solid waste handling have the resources to invest in better facilities and facilities that pollute less.

David Roberts:   

Food waste seems like a difficult problem. Are there technological solutions to food waste, or is this mostly a behavior issue that we need to educate people about? 

Sarah Smith: 

One of the groups that works on this is called ReFED; I spoke with their executive director a couple of years ago, and he was telling me that there are policy changes that can help, like shifting dates on packaging to ensure that there's maximal time to use the food while safe, improvements in packaging, technology, and so forth. That can all help, but I'm not an expert in food waste.

David Roberts: 

Tell us about the global methane pledge that President Biden just announced. Is it ambitious enough? Do we think that countries signing the pledge will actually do what they're saying they will do?

Sarah Smith: 

EU president Ursula von der Leyen and President Biden together announced this pledge recently. They called on countries around the world to join them in a collective effort to reduce global methane from all sectors by at least 30 percent below 2020 levels by 2030, and, importantly, also to take comprehensive domestic action to achieve this target. So this is a great step in the right direction.

David Roberts: 

So you think 30 percent by 2030 is a good target?

Sarah Smith:

I do, especially when compared to the 2020 baseline. This would be a big step toward keeping a 1.5 degree C of warming future in reach.

David Roberts:

Is this styled like the Paris Agreement, where countries are proclaiming they'll do this and we're trusting them based on their goodwill? 

Sarah Smith: 

This is a voluntary pledge, yes. I think of it as the launchpad for deep work in every one of these countries, to ensure that policies are put into place and actions are taken on the ground to get these tons of methane out of the air and try to stave off irreversible changes to the climate.

David Roberts:

Is it fair to say that there's no way to stop short of 1.5 degrees without getting ahold of methane?

Sarah Smith: 

Yes. We cannot keep 1.5 degrees in reach without wringing all of the methane that we can out of the system.

David Roberts: 

Catch us up on US methane policy. What policies do we have in place, especially with oil and gas? What are the big fights going on right now?

Sarah Smith:  

Fortunately, the US is poised to lead by example on this issue, through new rules from the US Environmental Protection Agency and through action by Congress this year that could put us on strong footing going into the COP and bring more countries onto this pledge.

David Roberts: 

This fight has been going on for a long time. Obama’s EPA put some standards in place, didn’t it?

Sarah Smith:  

Yes. President Obama's EPA developed standards for new and modified oil and gas sources, but left on the table emissions from the vast network of existing polluting oil and gas equipment all across the country. That is something that EPA Administrator Regan under the Biden administration has committed to addressing in forthcoming standards that should be out publicly in the next month.

David Roberts: 

So there are no federal standards on existing wells and mines?

Sarah Smith:

That's right. They are allowed to release unlimited methane right now.

David Roberts: 

Are Obama's standards on new and modified sources still in place, or did Trump mess with those?

Sarah Smith: 

He certainly tried. They were off the books briefly, but Congress took action through the Congressional Review Act and undid the Trump rollback so that the Obama rules are largely back in place. But they need to be updated, because we've learned a heck of a lot about methane reduction since 2015 and 2016, when those rules were written. We now know emissions could be cut in the US by 65 percent at least, using currently available, low-cost technologies.

We know more about how to solve the problem from states that have stepped up and taken leadership on this issue, including Colorado, which has gone through several rounds of rulemakings on this, and even the state of New Mexico, which recently took on flaring. Both Colorado and New Mexico now have finalized phase-outs for flaring of associated gas. Producers are going to have to stop routine flaring and capture the gas, except in emergency situations.

David Roberts:

Has Colorado shown success? Are methane emissions in Colorado declining? 

Sarah Smith: 

The latest data I've seen does show a declining leak rate in Colorado, and I expect that trend to continue with the state continuing to take leadership on this issue.

David Roberts: 

I’ve read that the Democrats’ reconciliation bill is meant to include a methane fee. What can you tell me about that?

Sarah Smith: 

This is a modest fee proposal that would reinforce the specific regulatory requirements that EPA is working on. It would raise revenue, much of which would go to EPA and could help the agency implement the provisions of the rules, improve reporting and monitoring, and even fund environmental restoration projects, including in communities that have been most impacted by air pollution from industry and climate change.

David Roberts: 

Is it intended mostly as a revenue raiser? 

Sarah Smith: 

That’s the main thrust, but it's important to note that it would also help reduce emissions quickly and provide an incentive for companies to go above and beyond the regulations that get promulgated under the Clean Air Act.

David Roberts: 

What is the oil and gas industry's current posture toward these upcoming rules? Are they still dug in in opposition? 

Sarah Smith: 

I would be hesitant to put the whole industry into one bucket on this. The seas are shifting. Some companies, over the course of the past couple of years, have started to support methane regulation. Even API, the industry trade association, has changed their messaging on this to be much more supportive. I think they see the writing on the wall.

David Roberts:  

I know they're protesting the fee. They say it's duplicative or it's on top of the rules, it's confusing. Do you put any credence in those kind of objections?

Sarah Smith:  

No, I really don’t. This is an industry that could so easily minimize its pollution, has had a chance to do that, and hasn't acted quickly enough. So it's time for the hammer to come down.

David Roberts:

It seems like it would be a political and public relations boon for an oil and gas company to say, “we're going to be a different kind of oil and gas company, we're going to be responsible and clean up our methane emissions.” They could do it at low cost and reap such a PR bonanza. Why have none of them done this, not even a single outlier? Do you have any theories about this?

Sarah Smith: 

I wish I could sit each one of the CEOs down with you, David, because that's exactly right. I think it's a case of short-sightedness, and, in some cases, prioritizing short-term gains over long-term gains.

David Roberts: 

Globally speaking, where are the other big methane sources? What other countries are particularly bad on this? Are there other countries taking action like the US? 

Sarah Smith:

Sadly, there are methane emissions coming from every continent, every country. Because they're so dispersed, we need global action on this global problem. Many of the big economies are the bigger sources right now, but not exclusively. 

In terms of where we're seeing action, it’s exciting to see the US stepping up, and I'll be curious and hopeful to see strong rules coming out this year and finalized next year. The European Commission has a methane strategy that cuts across a range of sectors; they're starting out with some legislation later this year on the oil and gas sector that will, we hope, take action on venting and flaring, leaks, monitoring, reporting, and the topics that we've discussed today. This would be across the EU.

Hopefully the EU will also establish import standards for all of the gas it's purchasing. It's currently the number one importer of gas in the world, so that will put pressure on Russia and Algeria and Qatar and some of these other countries that are supplying fuel into the EU to implement these common-sense best practices.

David Roberts:

I think of Russia as a huge source of natural gas. Is Russia taking action?

Sarah Smith: 

President Putin spoke about the need to reduce methane and called for global action on the topic during the leaders summit that President Biden organized on climate earlier this year, so it'll be interesting to see how that unfolds. Ultimately, we need certification and monitoring to ensure that the practices are actually being implemented on the ground, and the emissions are being prevented. 

David Roberts: 

This radical global transparency on methane emissions seems like it's going to be fascinating to watch from an international politics point of view.

Sarah Smith:  

It will be. We're going to know a lot more about methane sources and a lot more about carbon dioxide sources, too. I hope both can be tackled simultaneously — they absolutely must be to have a chance of maintaining a safe climate.

David Roberts: 

Do you think there will be substantial developments on methane in the upcoming COP?

Sarah Smith: 

I am hopeful that methane could be a bright spot out of this upcoming COP, and that this global methane pledge, when formally launched, will bring together many more countries to rein in the pollution.

David Roberts: 

It sounds like there's more and easier potential action on methane than on CO2, in some ways.

Sarah Smith: 

It is the low-hanging fruit that has been hiding just out of sight for a long time, and I'm hoping that it will start getting plucked.

David Roberts:  

It would be truly embarrassing if humanity destroyed itself with a pollutant that it could have reduced at no cost. That would be a terrible epitaph. Thank you, Sarah, for coming on and taking the time. It's very clarifying. 

Sarah Smith: 

It was fun to speak with you.