Containing methane and its contribution to global warming

February 28, 2020
International Institute for Applied Systems Analysis
Methane is a gas that deserves more attention in the climate debate as it contributes to almost half of human-made global warming in the short-term. A new study shows that it is possible to significantly contribute to reduced global warming through the implementation of available technology that limits methane release to the atmosphere.

Methane is a gas that deserves more attention in the climate debate as it contributes to almost half of human-made global warming in the short-term. A new IIASA study shows that it is possible to significantly contribute to reduced global warming through the implementation of available technology that limits methane release to the atmosphere.

According to the study published in the journal Environmental Research Communications, it is possible to achieve reduced global warming in the near term by targeting methane through the fast implementation of technology to prevent its release to the atmosphere. This could mitigate some of the otherwise very costly impacts of climate change that are expected over the next few decades. To achieve the significant reductions in methane emissions caused by humans needed to meet the Paris Agreement, we however need to know exactly where and from what sources emissions are emitted so that policymakers can start developing strategies to contain methane and its contribution to global warming.

“To develop policy strategies to mitigate climate change through reductions of global non-CO2 greenhouse gas emissions like methane, we need detailed inventories of the sources and locations of current human-made emissions, build scenarios for expected developments in future emissions, assess the abatement potential of future emissions, and estimate the costs of reducing emissions. In this study, we looked at global methane emissions and technical abatement potentials and costs in the 2050 timeframe,” explains study lead author Lena Hoglund-Isaksson.

Using the IIASA Greenhouse Gases — Air Pollution Interactions and Synergies (GAINS) model, the researchers endeavored to find out how well the GAINS bottom-up inventory of methane emissions at country and source-sector level between 1990-2015 match top-down estimates of the global concentration of methane measured in the atmosphere. In addition, they wanted to see how much methane would be emitted globally until 2050 if we take no further measures to reduce emissions.

The results show that at the global level, the GAINS methane inventory matches the top-down estimate of human-made methane emissions’ contribution to the atmospheric concentration of methane quite well. A reasonable match between bottom-up and top-down budgets, both at the global and regional levels, is important for the confidence in bottom-up inventories, which are a prerequisite for policy strategies to be perceived as “certain enough” by stakeholders in climate mitigation.

The authors’ analysis revealed a strong increase in emissions after 2010, which confirms top-down measurements of increases in the atmospheric methane concentration in recent years. According to this study, these are explained by increased methane emissions from shale gas production in North America, increased coal mining in countries outside of China, for instance, Indonesia and Australia, and increased generation of waste and wastewater from growing populations and economic development in Asia and Africa. In addition, the findings showed a small but steady increase in emissions from beef and dairy production in Latin America and Africa, highlighting how different the distribution of emission source sectors are across different world regions.

The findings further show that without measures to control methane emissions, there would be a global emission increase of about 30% until 2050. While it would technically be possible to remove about 38% of these emissions by implementing available abatement technology, it would still mean that a significant amount of methane would be released between 2020 and 2050, making it impossible for the world to stay below 1.5°C warming.

With that said, the researchers point out that technical abatement potentials can still be used to achieve considerable reductions in methane emissions in the near-term and at a comparably low cost. Between 30% and 50% of future global methane emissions can be removed at a cost below 50 €/t CO2eq. The use of fossil fuels will however also have to be phased-down to really make a difference. Technical abatement potentials are particularly limited in agriculture, which suggests that these emissions must be addressed through non-technical measures, such as behavioral changes to reduce milk and meat consumption, or institutional and socioeconomic reforms to address smallholder livestock herding as a means of risk management in Africa and South-East Asia.

“There is no one-size fits all solution for the whole world. In the Middle East and Africa, for instance, oil production is a major contributor to methane emissions with relatively extensive potentials for emission reductions at low cost. In Europe and Latin America, dairy and beef production are the main sources with relatively limited technical mitigation potentials, while in North America it is emissions from shale gas extraction that can significantly contain emissions at a low cost. Our study illustrates just how important it is to have a regional- and sector-specific approach to mitigation strategies,” concludes Hoglund-Isaksson.

What Is Nitrous Oxide and Why Is It a Climate Threat?

Despite its increasing role in global warming and effect on the ozone layer, little has been done to rein in this climate pollutant. One big reason: agriculture.

The majority of nitrous oxide comes from agriculture, including microbes in fertilized soils and animal manure. Credit Moenkebild/Ullstein Bild via Getty Images

The majority of nitrous oxide comes from agriculture, including microbes in fertilized soils and animal manure. It is a potent greenhouse gas with about 300 times the heat-trapping power of carbon dioxide. Credit Moenkebild/Ullstein Bild via Getty Images

When it comes to the global climate crisis, carbon dioxide emissions represent a problem that’s massive, intractable and running short on time to solve. But it’s not the only problem.

Other pollutants are rapidly warming our climate, too, sending scientists on a race to understand their implications before it’s too late. For years, experts have warned about the risks from one pollutant in particular—nitrous oxide—and yet there’s been little global action on it.

The reason: “It is intimately connected to food,” said Ravi Ravishankara, an atmospheric chemist at Colorado State University who co-chaired a United Nations panel on stratospheric ozone from 2007 to 2015.

Nitrous oxide is 300 times more potent than carbon dioxide, and it also depletes the ozone layer. Since it also has a shorter life span, reducing it could have a faster, significant impact on global warming.

But the largest source of nitrous oxide is agriculture, particularly fertilized soil and animal waste, and that makes it harder to rein in. “One could imagine limiting carbon dioxide, less methane, less of lots of things. But nitrous oxide is so much a food production issue,” Ravishankara said.

Chart: Where Does N2O Come From?

Since the 1960s, fertilizer use has shot up globally, helping usher in the “Green Revolution,” which fed millions around the world. In the U.S. alone, the use of fertilizer has risen more than 200 percent over the past 60 years, even though the amount of cropland has stayed relatively constant. At the same time, the number of large industrialized livestock operations has also gone up, creating more manure “lagoons” and excess manure, which is often over-applied on cropland.

2013 report by the United Nations found that since the pre-industrial era, nitrous oxide emissions from human activities have increased 20 percent. At the time, the authors wrote that if nothing was done, those emissions were expected to double by 2050.

Despite nitrous oxide’s role depleting the ozone layer, it is not included in the Montreal Protocol on Substances that Deplete the Ozone Layer, an international treaty that aims to restore the ozone layer by phasing out certain substances.

Here’s what you should know about the potent pollutant:

So, What Is Nitrous Oxide?

Like other greenhouse gases, nitrous oxide absorbs radiation and traps heat in the atmosphere, where it can live for an average of 114 years, according to the EPA. That puts it in a sort-of middle ground of super pollutants.

Compared with carbon dioxide, which can live in the atmosphere for hundreds of years, nitrous oxide is around a relatively short time. But it stays in the atmosphere longer than other short-lived climate pollutants like black carbon (which exists in the atmosphere for days) or methane (which is around for 12 years).

[Read more about short-lived climate pollutants here.]

Chart: Nitrous Oxide's Percentage of U.S. Greenhouse Gas Emissions

Nitrous oxide also poses a second threat: while in the stratosphere, nitrous oxide is exposed to sunlight and oxygen which converts the gas into nitrogen oxides. Nitrogen oxides can damage the ozone layer, which humans rely on to prevent most of the sun’s ultraviolet radiation from reaching earth’s surface.

That double-threat effect results in the gas’s potency. One pound of N2O warms the atmosphere about 300 times the amount that one pound of carbon dioxide does over a 100 year timescale. Its potency and relatively long life make N2O a dangerous contributor to climate change.

Where Does Nitrous Oxide Come From?

About 40 percent of nitrous oxide emissions come from human activities, and of those, the majority are from the way we use land—particularly agriculture. In the United States, about 75 percent of all N2O emissions from human activity are attributed to agriculture.

Especially in larger farming operations, livestock manure presents a two-fold emissions problem: it emits an enormous amount of methane, but it can create nitrous oxide too. “When the manure doesn’t get access to oxygen, toward the bottom of the pit, it starts to convert into nitrous oxide,” said Ben Lilliston, Director of Rural Strategies and Climate Change at the Institute for Agriculture and Trade Policy. “This also happens when manure gets overapplied to crop land.”

When farmers add nitrogen fertilizer to their soil to help stimulate plant growth, only about half gets taken up by the plant, according to Neville Millar, a senior research coordinator at Michigan State University. The rest can be washed away in groundwater, or off-gassed as nitrous oxide or other gases.

Chart: N2O Emissions Have Been Rising

Agriculture isn’t the only culprit, though. Nitrous oxide is also emitted when fuels are burned, though how much depends on what type of fuel, and which combustion technology is used. It’s also generated as a byproduct of the production of chemicals like nitric acid (used for fertilizer) or adipic acid (used to make nylon and other synthetic products). The treatment of domestic wastewater can also generate nitrous oxide.

What About Natural Sources?

In the summer of 2013, a pilot flew a tiny plane low over thawing Arctic permafrost as part of a study to determine what climate-forcing pollutants were being emitted and how much. The researchers behind the study, a team from Harvard and NOAA, thought they would find methane—and they did.

Permafrost is frozen land that contains ancient soil, sediment and organic material from plants and animals. It covers about a quarter of the Northern Hemisphere. As the Arctic warms at roughly twice the rate of the rest of the world, permafrost is beginning to thaw, and as it does, the ancient materials are exposed to oxygen, which causes them to release gases that are further contributing to warming.

Researchers globally have been trying to understand just how much methane could be contained in the permafrost. But the data collected in 2013—and published in a report in the journal of Atmospheric Chemistry and Physics earlier this year—also showed that nitrous oxide was also being emitted from the permafrost, at roughly 12 times the rate previously assumed.

“When I hit that first result, I went back through them and calculated them again. I thought I had made some little error,” said Jordan Wilkerson, a graduate student who first discovered the nitrous oxide. “I looked a couple times and got the same answer.”

The study covered about 120 square miles and only during the month of August. As such, it’s hard to extrapolate what these findings could mean Arctic-wide.

But what’s significant, says NOAA’s Ron Dobosy, who was a co-author on the study, is that until Wilkerson’s discovery, the Arctic was considered to be very nitrogen poor. Now it’s clear that nitrous oxide emissions are present, and need to be studied further. “Methane is being covered more and more heavily. It’s time for nitrous oxide to be covered more too,” said Dobosy.



Cows that have been genetically modified so they burp and fart less could have a major impact on climate change—potentially helping to reduce global warming by cutting methane emissions by half, scientists have said.

Methane is a greenhouse gas that is far more potent than carbon dioxide. It is released when biological material breaks down, such as during a cow’s digestive process. While the burning of fossil fuels is by far the biggest contributor to anthropogenic climate change, methane from the agriculture industry also has a role to play—and this mostly comes from cattle releasing the gas.

Previously, scientists have proposed different ways to reduce methane emissions from livestock, such as introducing dietary changes. However, this is unlikely to make a big difference in terms of climate change.

In a study published in Science Advances, a team of researchers has identified a group of genetically inherited gut microbes that regulate how much methane a cow produces. By finding these microbes, researchers could find a way to manipulate them so the cow produces far less methane.

“Most gases are emitted at the front end of the cow; at least 90 percent of the methane is burped,” study author John Wallace told Newsweek. “If methane production is inhibited, there would usually be less gas emitted.”

The team examined over 1,000 dairy cows from the U.K., Finland, Italy and Sweden. They looked at variations between genes before identifying a core microbiome that was present in half of the animals. A computer algorithm was then used to predict methane emissions based on the composition of the microbiome.

Researchers believe that based on their findings, cows could be selectively bred to produce fewer methane emissions—by finding the lowest methane producing cows and breeding them, while leaving out the high emitters. By getting rid of the biggest emitter, methane could be cut by 50 percent, Wallace told New Scientist.


“We know of no downside to lowering methane emissions in this way,” Wallace said. “However, there is no upside either—except for the environment.” In the study, the scientists also looked at whether reducing emissions would help to increase milk production—but it did not. “This is important, because improved feed efficiency would have been a great selling point to the farmer and breeder,” Wallace continued. “Our alternative strategy would be to use our data to breed for improved feed-to-milk efficiency using the microbiome as selection trait. That would lower methane emissions too.”

He said the next step will be to work out exactly what bovine genes are involved in the process and what they do.

File photo. The agriculture industry is a major source of methane.ISTOCK

Scientists are baffled by a giant spike in this greenhouse gas (it’s not CO2)

Stephen Simpson / Getty Images

The unexpected culprit that could throw a wrench in the world’s efforts to stop climate change? Runaway methane levels. Researchers monitoring air samples have noticed an alarming observation: Methane levels are on the rise and no one’s quite sure why.

NOAA’s Earth System Research Laboratory scientists have been analyzing air samples since 1983. Once a week, metal flasks containing air from around the world at different elevations find their way to the Boulder, Colorado, lab. The scientists look at 55 greenhouse gases, including methane and its more-famous climate villain, CO2.

You might know methane as the stuff of cow farts, natural gas, and landfills. It’s also an incredibly potent greenhouse gas, absorbing heat 25 times more effectively than CO2. While the rise of carbon dioxide has been stealing thespotlight as of late, methane levels have also been on the incline.

Methane levels, not surprisingly, have been steadily rising since the Industrial Revolution. Things picked up in 1980 and soon after, the NOAA scientists began consistently measuring methane. Levels were high but flattened out by the turn of the millenium. So when levels began to increase at a rapid rate in 2007, and then even faster in 2014, scientists were baffled. No one’s best guesses came close to predicting current methane levels of around 1,867 parts per billion as of 2018. This means studies evaluating the effects of climate change and action plans to address them, like the Paris Climate Agreement, may be based on downplayed climate crisis forecasts.

Methane levels from 1950 to present. 2° Institute

So what’s the big deal? Carbon dioxide emissions are relatively well understood and can be tracked to various human activities like transportation and electricity, which means policies can be enacted to target and lower emissions. Pinning down the source of methane, on the other hand, is a little more complicated.

“The really fascinating thing about methane,” Lori Bruhwiler, a NOAA research scientist, told Undark, “is the fact that almost everything we humans do has an effect on the methane budget, from producing food to producing fuel to disposing of waste.”

As if things weren’t complicated enough, a study published in AGU100 distinguished microbe-produced methane from fossil fuel methane — historically the more abundant one — and found that “natural” methane had taken the lead. This unexpected result might explain the upticks in methane levels that do not seem correlated with human activity. Of course, it could also be any number of human-made causes, including warming temperatures freeing up the gas and more frequent floods amplifying the methane output of wetlands.

Natural methane or not, this finding doesn’t exonerate anyone. The study’s authors made that clear in their concluding remarks.

“If the increased methane burden is driven by increased emissions from natural sources,” they wrote, “and if this is a climate feedback—the warming feeding the warming—then there is urgency to reduce anthropogenic emissions, which we can control.”

Curbing methane could be a powerful tool in our upcoming climate fight. Since the greenhouse gas is relatively short lived, only around 12 years, versus the 20 to 200 years of CO2, and is more effective at trapping heat than carbon dioxide, addressing methane emissions could be effective as a short-term climate remediation tool. The first step? Bringing more attention to methane so we can figure out where it comes from and nip it in the bud.

A missed chance for a radical rethink

A flawed report from the Parliamentary Commissioner for the Environment makes little contribution to the development of our climate policies, writes Rod Oram.

Parliamentary Commissioner for the Environment Simon Upton has produced a remarkably unbalanced report on our attempts to tackle climate change. On one hand he’s punishingly hard on fossil fuel emitters; on the other he’s complacently soft on agricultural emitters.

He’s wrong on both. Fossil fuel emitters need far more help and incentives to play their emissions reduction role than he suggests; and agricultural emitters will have to make a far bigger transition to radically different farming techniques, types of food and land use than he believes. Farmers need more help than the easy life in an ETS split between the two types of emissions, which he advocates.

He is also wrong to attempt to split fossil fuel emissions and biological emissions into two separately managed camps. Yes, there are significant differences between the two in terms of origins and climate impacts. But there are also great synergies to be achieved in an integrated system to tackle climate change. For example, new sources of clean energy adopted by urban New Zealand will help farmers; and new environmental management techniques they will have to pioneer will help urban New Zealand manage its ecosystems better.

He also makes a flawed case for reserving trees for offsetting farming emissions. He argues the two are connected because they are biological systems. But the trees only sequester the residual carbon dioxide left after agricultural methane breaks down. But in its short-life, methane is an immensely potent driver of climate change. Moreover, the trees don’t sequester nitrous oxide, the other powerful agricultural emission.

Therefore, to truly offset the climate impacts of farming’s methane and nitrous oxide, we would need to plant a prodigious volume of trees to absorb large volumes of carbon dioxide from fossil fuel emissions to give us the equivalent reduction in climate impact. But he’s opposed to that.

He is right, though, about two aspects of trees. They have a far shorter life than the carbon dioxide they sequester. Therefore, they are only a temporary and partial solution to reducing emissions while the world works on technologies for deep cuts in emissions and permanent sequestration; and blanket planting of short-lived tree species for harvesting, predominantly radiata pine, is damaging to ecosystems, landscapes and communities.

But again, we could better address those two issues in an integrated system, rather than the split one he advocates. For an in-depth description of his approach, please read this Newsroom article by Eloise Gibson, our environment and science editor.

When it comes to agriculture’s impact on the land and climate, Upton offers an important historic insight:

“While most attention is currently directed to agricultural greenhouse gases, land use change emerges as New Zealand’s biggest contribution to global warming. More than 3 billion tonnes of carbon have been shifted to the atmosphere from the land, largely as the result of forest clearance to make way for agriculture. The approximate scale of warming associated with these changes is estimated to be around seven times larger than our contribution of fossil emissions.”

Yet, he misses the current significance of agriculture’s impact on climate here and around the world. In aggregate through land use changes and emissions from artificial fertiliser use, raising of ruminant animals and cultivating rice paddies, agriculture is the biggest driver of climate change, bigger even than fossil fuel use.

For example, ruminant animals globally produce roughly one-third of anthropogenic methane emissions. Here in New Zealand biological methane from agriculture accounts for around 86 percent of New Zealand’s total methane emissions, and with nitrous oxide, nearly half our total emissions.

Evidence is accumulating rapidly that we need massive changes in current agricultural practices and the food they produce.

“Civilisation is in crisis. We can no longer feed our population a healthy diet while balancing planetary resources. For the first time in 200,000 years of human history, we are severely out of synchronisation with the planet and nature. This crisis is accelerating, stretching Earth to its limits, and threatening human and other species’ sustained existence.”

So declared The Lancet’s editorial accompanying the study released earlier this year by its Commission on the global food system. The joint project by the British peer-reviewed medical journal and EAT, a Scandinavian NGO, involved 37 leading scientists across relevant disciplines from 16 countries. For full coverage, please read this column I wrote in February.

Such views are expressed by other leaders, such as Catherine Geslain-Laneelle, France’s candidate for the role of the UN’s Food and Agricultural Organisation, as Newsroom recently reported.

… he appears to have a one-dimensional view of farming and climate.

Upton, though, does not share the anxiety of such scientists. In his report, he writes: “If global diets change away from red meat and dairy products to diets based on crops and non-ruminant animals (e.g. chicken), this would result in lower biological emissions and may also reduce other environmental impacts. These are certainly things New Zealand farmers could consider, but it should be noted that New Zealand’s food production is largely driven by overseas food demand.”

Upton’s passive view of NZ farmers being market-led is at odds with his view that as “an agricultural leader, any action taken by New Zealand to mitigate biological emissions will be noted internationally.” And as “an acknowledged leader in both the measurement and management of biological sources and sinks, New Zealand cannot avoid taking a leading role in this debate.”

Moreover, he appears to have a one-dimensional view of farming and climate. “Climate is just one of a number of stressors that plague our landscapes. Water pollution, soil depletion, biodiversity loss and pest invasions are just some of the problems.” Yet, the big changes in farming systems needed to address climate change would also significantly help to heal those related ills too.

That understanding of the bigger, inter-dependent factors at work in farming on climate change and related issues is far more thoroughly explored by the Productivity Commission in its massive report on our transition to a low emissions economy, by Vivid Economics for GLOBE-NZ, the all-party group of backbench MPs, and by Jan Wright, Upton’s predecessor as Parliamentary Commissioner for the Environment.

Upton only briefly summarises the emissions-reducing science and technology pathways opening up for farmers. He does not explore, as some of the above authors have, how these and other factors at home and aboard will significantly shift farming systems and land use here in the next few decades.

By ignoring such analysis, he significantly undercuts the case he makes for separating emissions from fossil fuels and biological emissions into two separate regimes. Where he does make a connection, he makes a serious error. He writes: “Farmers are also heavy users of fossil fuels when it comes to processing raw materials and moving commodities to market. So they would face the same fossil emissions prices for those activities as other fossil emitters.”

But as Fonterra, the largest single source of emissions by far in our economy, points out, emissions from its manufacturing, transport and distribution only account for 10 percent of its overall emissions. Moreover, it is reserving the right to still be building new coal fired plants in 2030. Those could have a life of up to 30 years.

Energy emissions on farm are minimal. The other 90 percent of Fonterra’s overall emissions are on farm from animals and artificial fertiliser. On those, Fonterra is only pledging to keep its methane levels unchanged by 2030. If its farmers achieve any reduction in methane per litre of milk a cow produces, it will put the gains to higher milk volumes.

In contrast, Upton offers little comfort to fossil fuel emitters: “For industries where fossil emissions may be hard to reduce because no realistic alternatives exist, a number of pragmatic industry-specific solutions could be explored. These include the continuing use of free allocations, access to international units and using some of the NZ ETS revenues for the research and development of low carbon technologies for these industries.”

Such an approach, though, would do little to deliver the steep reduction in such emissions Upton rightly argues for. Thus, his report will make only a minor contribution to the development of our climate policies. It won’t cause the radical rethink he is arguing for.

Climate action committee urges redirection of Irish agriculture

Agriculture sector, Ireland’s biggest, remains ‘largest emitter of greenhouse gases’

A dairy cow fixed with technology that collects and measures methane emissions grazes at Moorepark Teagasc food research centre in Fermoy, Co Cork. Photograph: Rachel Doyle

A dairy cow fixed with technology that collects and measures methane emissions grazes at Moorepark Teagasc food research centre in Fermoy, Co Cork. Photograph: Rachel Doyle

A fundamental redirection of Irish agriculture, including diversification away from heavy reliance on dairy and beef production, is among the recommendations of the all-party Committee on Climate Action report due to be published on Thursday.

The agriculture sector – Ireland’s biggest industry – remains “the largest emitter of greenhouse gases”, the report finds, while “Ireland cannot meet its international emissions targets without tackling agricultural sector emissions”.

A key aspect of successful efforts to reduce emissions associated with agriculture “will be land-use diversification”, it concludes. The committee accepts farmers will need support to reduce greenhouse gas (GHG) emissions, “while ensuring they can make a living for their families”.

According to the latest draft of the report, diversification of the Irish farm system will require increased horticulture production, and should follow the UK approach, where there is “a move away from an overreliance on single modes of production”.

There is a need for a more diversified, resilient, sustainable and equitable model for Irish agriculture

This, it adds, will help adaptation to the effects of climate change. “Extreme weather events of the last 12 months (storms, snow, heatwave and drought) illustrate the vulnerability of the sector to climate change and highlight the need for adaptation.”

Furthermore, it accepts “there is a growing global trend, supported by advice in recent scientific studies, towards a more plant-based diet. The trend towards more plant-based diets represents a commercial opportunity which Irish horticulture should avail of in the transition to a sustainable, low-carbon food system.”

Underlying what’s envisaged, it adds: “There is a need for a more diversified, resilient, sustainable and equitable model for Irish agriculture. This must now form the central component of a long-term strategy development for Irish agriculture moving forward.”

National plan

The Government has agreed to take on board the committee’s recommendations in its own plan to be published next month, and it will feed into the National Energy and Climate Plan to be submitted to Brusselsby the of 2019.

The committee, chaired by Fine Gael TD Hildegarde Naughton, endorses all 28 measures contained in “a mitigation pathway” produced by Teagasc, which it says should be adopted by the Government in an implementation plan with the Department of the Taoiseach playing a lead role.

It notes that while carbon efficiency has improved based on per head of cattle, milk production, due to expansion in the dairy sector, had led to an 8 per cent increase in emissions between 2012 and 2016.

It also highlights risks associated with increased specialisation in beef and dairy farming “which has the highest climate impact via methane emissions”.

“There are currently ambitious targets aimed at adding value in the sector under FoodWise 2025. Exports are expected to reach €19 billion, which without diversification of the sector will inevitably drive higher levels of ruminant-based production and place GHG emissions on a continued upward trajectory, even with improved efficiency gains,” it adds.

The committee agrees a national review of land use “would be extremely useful in understanding of how to optimise planning”.

It does not agree, however, to proceeding with a carbon tax on farmers, as had been recommended by the Citizens’ Assembly, with revenues reinvested to ensure adoption of climate-friendly farming – though it recommends evaluation of how it might apply in the future.

Fianna Fáil spokesman on climate action Timmy Dooley confirmed the significance of what is set to be achieved on agriculture on an all-party basis. He said the sector recognised the need for significant change “and they are up for it”. While Teagasc had done good work on how to respond to the emissions issue, the transition for the sector would be challenging.

There was no point in applying a carbon tax specifically on farming activity unless alternatives were in place, he added.

What had been agreed was a comprehensive agreement on better land use; expansion of renewable energy in farming including deployment of anaerobic digesters, improved use of afforestation and a rewetting of bogs to capture carbon. These, in his view, amounted to “big actions” underpinned by an immediate implementation timeframe.

Sorry, Alexandria Ocasio-Cortez, but “farting cows” aren’t the problem

Flickr / Dimitri Rodriguez

The proposed language in the Green New Deal got this wrong. Will it be corrected?


Representative Alexandria Ocasio-Cortez, the legislator behind the Green New Deal, wants to take away our hamburgers. At least, that’s what a vocal group of Republican politicians would have you believe.

The congresswoman’s vision for environmental reform, they say, amounts to a de facto ban on beef. Rather than engaging the public on the finer points of the non-binding resolution, which she co-introduced with Massachusetts Senator Ed Markey on February 7, these critics are appealing to our stomachs, and conjuring an America under gustatory austerity, a nation where we can’t eat what we want.

These claims are political theater. And yet, in recent weeks, AOC has backed down from an inflammatory talking point about cow farts, and their role in climate change. Now, an outspoken member of the scientific community says he had an impact behind the scenes, and the politician’s public stance on ruminant flatulence has evolved out of deference to the facts.

How did we get here?

It started with the release of a fact sheet outlining the much-debated resolution’s key points. Shortly after Ocasio-Cortez’s office released the document, her office said it was a draft published by mistake, and retracted it. By then, she was already getting dragged for some of its proposals. That very public resistance has only increased over the last month.

If you don’t hear about cow farts anymore from AOC, it may not be because of GOP criticism.

Some of the fact sheet’s most controversial language, it turned out, wasn’t about planet-warming carbon dioxide—the kind released when fossil fuels like gasoline, coal, and oil are burned—but methane, specifically the kind that comes from animal digestion. The since-deleted document proposed a goal of taking America carbon-neutral in ten years, noting that a more aggressive timeline isn’t possible because “we aren’t sure that we’ll be able to fully get rid of farting cows and airplanes that fast.”

That particular line set off a firestorm from the right. President Trump interpreted it to mean that Americans wouldn’t be able to “own cows anymore.” Republican Senator John Barrasso of Wyoming said it meant goodbye “to dairy, to beef, to family farms, to ranches.” Then AOC went on TV and defended it.

As it turns out, neither side was accurate. Republicans are likely to continue linking Green New Deal priorities to a supposed hamburger ban. But if you don’t hear about cow farts anymore from AOC, it may not be because of GOP criticism. Frank Mitloehner, an animal scientist and air quality specialist at the University of California, Davis, insists cattle flatulence isn’t the problem it’s made out to be, and says he helped set the record straight.

Here’s what seems to have happened. On February 4, shortly before Ocasio-Cortez announced the Green New Deal, she was speaking to school children in Queens, New York. When one asked how they could “combat” climate change, Ocasio-Cortez offered two practical options—stop using disposable razors, and skip meat and dairy for one meal.

Mitloehner tweeted at her.

“Dear @AOC: we all try to help the climate,” he wrote. “However, the two options you offered have low impacts compared to the 800lb gorilla, which is to reduce fossil fuel use. About ⅔ of greenhouse gas emissions in the US stem from transport and energy prod&use. Meat/milk = 4 % of total GHG,” referring to findings in a recent EPA report.

“I give her team a lot of credit for reaching out.”

Mitloehner says his tweet got the attention of the think tank that advisesOcasio-Cortez on climate policy. Last month, he says, he was contacted by Anna Scanlon, who runs outreach at New Consensus, a policy group that helped write the Green New Deal for the congresswoman’s office.

Why were they reaching out to him? Because the non-binding resolution calls for removing as many greenhouse gas emissions from the farm sector, which represent 9 percent of those total emissions in America, “as is technologically feasible.” Mitloehner, who studies how cattle emissions contribute to air quality, is well-liked by the meat industry, and has a knack for disarming fervent right-wingers, would seem a good source of information.

“I give her team a lot of credit for reaching out,” Mitloehner says. “If we really are serious about making a difference in carbon emissions, you cannot do this without agriculture involved.”

He says he was dismayed to see Ocasio-Cortez blaming “cow farts” for greenhouse gas emissions. Technically, she’s right: As cattle digest food, they release nitrous oxide and ammonia in their manure, gases that have planet-warming potential. But the more abundant greenhouse gas, methane, comes out mostly through their burps, which makes them a more significant driver of climate change. None of this is funny to Mitloehner, by the way, whose research involves putting cows in air-tight tents to measure the content of their “eruptions.”

Mitloehner claims that after his tweet, Ocasio-Cortez removed “all mentions” of cow farts from social media. I couldn’t find any such posts from her about said cows, and neither the congresswoman’s office, nor New Consensus, returned requests for comment. It is true, however, that the much-maligned fact sheet, and the line about “farting cows,” has disappeared. Briefly, its language was changed to “emissions from cows,” but that too was deleted. Mitloehner says Ocasio-Cortez’s policy team told him the reference was “pretty much a mistake” that was quickly remedied.

“Farting cows,” Mitloehner says, trivializes what’s otherwise a very serious issue

“I’m not saying that it was me who caused that,” he says. “But if it wasn’t me, then it was a coincidence that happened right after my communication with them.”

Specificity is important, Mitloehner insists. Being able to tell our farts from our burps, and our burps from our fossil fuels, is the first step to mitigating the effects from all of them. And wrapping that all up in “farting cows,” he says, trivializes what’s otherwise a very serious issue.

Other animal scientists, including Jason Rowntree, a forage expert at Michigan State University, share that point of view. He says the fixation around cow farts is “juvenile,” and “dumbs down the conversation from a scientific perspective.” He’s also of the perspective that cattle grazing has environmental benefits which are overshadowed by the issue of methane emissions.

“In the United States, when you look at different sources of methane, a much greater amount is actually coming from industries other than agriculture,” he says. “But because everything’s on the table, people look at every emission. And that’s how the cattle component has gotten in the crosshairs, so to speak.”

Beyond that discussion of how, exactly, enteric emissions work, Mitloehner hardly considers the Green New Deal a revolution, or a moonshot. There’s already a version of it in California—a scoping planthat requires, among other changes, a 40-percent reduction of methane and soot by 2030. He disagrees with it, methodologically, saying he’s not convinced that emissions are being adequately measured today, and therefore, that it’s premature to establish targets. But philosophically, he’s on board. Reducing “short-lived” gasses, such as methane, has an immediate effects on global temperature.

If all Americans adopted vegan diets, it would reduce the country’s carbon footprint by 2.6 percent.

In California, dealing with those gasses as they’re belched by cattle, and to a lesser degree, coming out the other end—mostly in the form of their manure—has been a challenge. To push larger-scale change, Mitloehner says, he doesn’t suggest shrinking the industry. Rather he wants to see technological solutions implemented, like experimental feed additives that reduce methane emissions, and anaerobic digesters, which transform manure into biogas. In Germany, there are 9,000 such digesters. California, by contrast, has “maybe two dozen.”

“Obviously, Germany has a different public policy around renewable energy,” he says.

Mitloehner complimented Ocasio-Cortez’s policy team for being engaged during a half-hour conversation about those solutions, and for having evident knowledge of some of those technological fixes, like seaweed being fed to cows to reduce methane content. That doesn’t mean, however, that they saw eye-to-eye on everything. When it comes to eating less red meat, for example, Mitloehner does concede that it can reduce greenhouse gas emissions. But only by a very small amount. A recent study, for example, showed that if the United States completely shifted away from animal farming, and all Americans went on a vegan diet, the move would reduce the country’s carbon footprint by 2.6 percent.

As crazy it sounded, I still had to ask him. Were the critics right? Were they onto something? Based on his conversation with the policy team, did he really think AOC was coming to take away your hamburgers?

“Honestly, I don’t think so,” Mitloehner says. “I’ve talked to the people she works with. And they were very reasonable.”

Correction: An earlier version of this article stated that a study modeled the environmental impact of 20 million Americans going on a vegan diet. In fact, it modeled the impact of all Americans on the diet. We regret the error.

It’s 2050 And This Is How We Stopped Climate Change

When NPR interviewed Rep. Alexandria Ocasio-Cortez in February about her Green New Deal, she said that her goal was bigger than just passing some new laws. “What I hope we’re able to do is rediscover the power of public imagination,” she said.

Well, we’re unleashing our imagination and exploring a dream, a possible future in which we’re bringing global warming to a halt. It’s a world in which greenhouse emissions have ended.

So — what does this world look like?

Solar panels fill a field in Provence-Alpes-Cote d’Azur, France.

Panoramic Images/Getty Images

Mass Electrification (Batteries Hold The Power)

(Editor’s note: Each story has two sections, the first reflecting the present and the second imagining the world of 2050.)

2019: I went looking for people who’ve mapped out this world without greenhouse emissions. I found them in Silicon Valley.

Sila Kiliccote is an engineer. The back deck of her house, high up in the hills, overlooks Cupertino. Apple’s circular headquarters is hidden in the morning mist. It’s a long way from Istanbul, in Turkey, where she grew up; a great place to conjure up future worlds.

“Maybe you’d like some coffee?” Kiliccote says.

Her coffee machine is powered by solar panels on the roof. So is her laptop and her Wi-Fi.

“Everything runs on electricity in this house,” she says.

This is the foundation of a zero-carbon world: Electricity that comes from clean sources, mainly the sun and the wind, cheap and increasingly abundant.

Today, it powers this house; tomorrow, it could drive the world.

Last year, Kiliccote quit her job at Stanford University and launched a startup company, eIQ Mobility, helping companies replace their fleets of vehicles, such as delivery vans, with electric-powered versions.

“In order to have impact, timely impact, I figured that I need to leave research and focus on impactful things that I want to do. And fast,” she says.

It has to happen really fast. Last year, the world’s climate scientists put out a reportshowing what it will take to limit global warming to 1.5 degrees C by the end of this century, averting the worst consequences of climate change. It requires bringing the globe’s net greenhouse emissions down to zero by 2050.

It’s a giant leap for humankind.

So Sila Kiliccote and I take that leap. Sitting in her kitchen, with solar panels overhead and an electric car parked outside, we pretend that it has happened. It’s 2050 and we’ve stopped climate change.

“Any sense of how we did it?” I ask her.

She pauses. “Yes,” she says.

2050: The first step was electric cars. That was actually pretty easy

“By 2025, battery technology got cheaper,” she says. Electric cars were no longer more expensive. “At that point there was a massive shift to electric vehicles, because they were quieter, and cleaner, and [required] less maintenance. No oil change! Yippee! You know?”

Heating and cooling in homes and office buildings have gone electric, too. Gas-burning furnaces have been replaced with electric-power like heat pumps.

We needed more electricity to power all this right when we were shutting down power plants that burned coal and gas. It took a massive increase in power from solar and wind farms. They now cover millions of acres in the U.S., 10 times more land than they did in 2020. Huge electrical transmission lines share electricity between North and South America. Europe is connected to vast solar installations in the Sahara desert, which means that sub-Saharan Africa also has access to cheap power.

“It just changed Africa,” Kiliccote says. “It actually fueled the economies of Africa.”

We now store electricity so that it’s always there when we need it. With batteries, of course, but in lots of other ways, too. For instance, cities are using electricity to heat and chill massive tanks of water, which then heat or cool buildings at any hour of the day or night.

Sila Kiliccote left Stanford University and founded eIQ Mobility, a startup company focused on helping companies electrify their fleets of vehicles.

Dan Charles/NPR

Sally Benson, co-director of the Stanford Precourt Institute for Energy, is so ready to take the leap and imagine this zero-carbon world 2050, it’s a little startling.

“I regularly take a helicopter, an electric helicopter, from here to San Francisco,” she assures me, totally deadpan.

“You can run a helicopter on batteries?” I ask, not quite believing it.

“Oh, yes! Oh, God, yes. That happened a long time ago,” Benson says, laughing. “That happened in the 2030s. That was great.”

But she says that even in this all-electric world, there are some holdouts. Some things have just been really hard to electrify.

Some big cement and steel plants still are burning coal or natural gas, but they also have to install massive plants to capture carbon dioxide from their smokestacks and put it back underground.

“We just had to kind of bite the bullet and say, ‘OK, if you’re making cement or steel, you are capturing and sequestering that CO2,'” Benson says. “And in some cases we actually had to say, ‘We’re not going to make those things here anymore'” because it wasn’t economically feasible to capture the CO2 emissions from that factory.

Big, long-distance freight trucks were a problem, too. “They’re really heavy, and batteries are really heavy, and if you have to put a whole bunch of batteries on a truck it’s really inefficient,” Benson says.

In some areas, like this one, our picture of the future gets a little fuzzy. Different guides to this 2050 world show me slightly different things.

Some of my guides see “electric highways” with wires overhead, and trucks tapping into the electric power in those wires the same way trains do. Others see trucks running on hydrogen fuel; we make that hydrogen using solar or hydro power.

It appears that aircraft still are burning jet fuel. When you buy a plane ticket, you’re also paying to cancel out that flight’s carbon emissions, capturing an equivalent amount of CO2 from the air. This makes air travel expensive. Fortunately, we now have much faster trains. Teleconferencing helps, too.

Sally Benson is absolutely convinced about one thing. The hardest part of this journey wasn’t finding technical solutions. They all existed, even back in 2019. The hardest part was navigating the social disruption.

“The transformations were so profound that it really needed to be a collective effort,” she says.

Entire industries died — like oil exploration and gas furnace manufacturing. Others rose to take their place, as the country rebuilt its electrical systems. People didn’t know what would happen and they were scared. The changes only moved ahead when people were convinced that they weren’t getting ignored and left behind. It was the political struggle of a generation.

Now, in 2050, there’s a tremendous sense of accomplishment.

“Are there children who look around at all the old buildings and say, ‘What are those things they call chimneys? What were they for?’ ” I ask.

“They do,” Benson says with a chuckle. “You know, it’s like a historical artifact, but you know, they find it very touching. They are appreciative, because they’re living in a world where they don’t need to worry about climate change anymore.”

It wasn’t easy and it wasn’t free, Benson says. But it was absolutely worth it.

The air is so much cleaner. Cities are quieter. And we’re no longer heating up the planet.

A streetcar rolls down King Street in downtown Toronto. Most car traffic has been diverted from this section of the street.

Dan Charles/NPR

The Urbanization Of Everything (A Desire Named Streetcars)

2019: I’m taking a walk through downtown Toronto, in Canada, with Jennifer Keesmaat, the city’s former chief planner.

Keesmaat wants me to see one particular street. King Street. It’s the seed of a zero-carbon future, she says.

King Street has a little bit of everything: glass-walled office buildings, theaters, old brick warehouses.

Two years ago, a new set of traffic rules went into effect here. “Basically, what we’ve done is, we’ve limited through-traffic for cars,” Keesmaat says. It forced cars away from King Street and launched a whole cascade of changes.

The streetcars that run down the middle of King Street weren’t stuck in traffic anymore.

They became the best way to get across town at rush hour. “The volume of people being moved is astronomical!” Keesmaat says, as one rolls by. The streetcars, of course, are powered by electricity, and one passes every two or three minutes.

Meanwhile, thousands of people have been moving into this downtown neighborhood, buying condos and renting apartments. Keesmaat knows one of them. He’s the father of one of her friends.

“He said to me a few weeks ago, he thinks he takes out his car about once every two weeks,” Keesmaat says. He walks to shops, restaurants and basketball games. His neighbors walk to jobs in the financial district right down the street. He’s not heating a big free-standing house, either.

He has cut his energy use, and his greenhouse emissions, dramatically.

“That wasn’t the driver for him,” Keesmaat says. “He didn’t say, ‘How do I in fact live smaller?” It just happened naturally in this new urban geography.

For a city planner, like Keesmaat, this is totally inspiring. “When we provide people with real choices, better choices, it can open up our minds!” she says. “We can change our minds about what we thought was the only way to live.”

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Jennifer Keesmaat is the former chief city planner of Toronto. She also hosts a podcast called Invisible City.

Dan Charles/NPR

2050: At this point, Keesmaat and I open up our minds and take a leap into a world that could be. Greenhouse gas emissions have dropped to zero.

How did we do it? By gradually reshaping our cities so that they look more like this neighborhood, with lots of people living close together, within walking distance of many of the things they need.

Keesmaat can already see this city in her mind, and describe it. “The vast majority of streets have been pedestrianized; that’s how people get around, by walking down the street,” she says.

“What has happened to the sprawling suburbs?” I ask. “Are people living there? How are they getting around?”

“Some of the large homes haven’t changed at all,” Keesmaat says. They’ve just been turned into multifamily units.” Other free-standing houses that once lined suburban cul-de-sacs have disappeared; each one has been replaced with a building that contains five or six homes. With the local population booming, those neighborhoods also attracted shops and offices. Suburban sprawl morphed into urban density.

Cars have mostly disappeared. “There are cars, but people don’t own cars,” Keesmaat says. “Because a car is something that you use occasionally when you need it.” Streetcars and buses go practically everywhere in the city now, and you rarely have to wait more than a couple of minutes to catch one. Fast buses and trains connect towns. For other destinations, there’s car-sharing.

“2050? It’s a wonderful life!” says Daniel Hoornweg, another one of my guides to this zero-carbon world. He’s a professor of energy systems at the University of Ontario Institute of Technology. Years ago, he wrote a big report on cities and climate change for the World Bank.

He also can describe this new city, and how it took shape. Local governments created it, he says. First, they gave people new ways to get around: subways, bike lanes, buses and streetcars.

But along with those carrots, there was also a stick. Cities took control of the precious real estate known as “roads” and started charging for the right to use them. “Maybe the most powerful thing that got us here, is [that] we got the pricing right,” he says. “So, you want an autonomous vehicle? Bless your heart, but it costs you more to drive that autonomous vehicle on the road by yourself. If you ride-share, it’s a little bit less.”

“And this is even if they are electric vehicles?” I ask.

“Even more if they’re electric vehicles!” Hoornweg says. Personal electric cars for everyone couldn’t solve the problem, he explains. First of all, electricity is precious. We can’t waste it powering everybody’s electric car.

Second, electric cars could have clogged the streets of our densely populated cities the same way gas-burning cars once did, back in, say, 2019. Our city of 2050 functions because streets are clear for buses and streetcars that carry dozens or even hundreds of people at a time.

The basic recipe — densely populated neighborhoods linked by mass transit —has been the same for cities all over the world, Hoornweg says. But the details came from constant experimentation. If an idea worked in one place, other cities snatched it up. For instance, way back in 1991 the city Curitiba, in Brazil, built dedicated roads for fast buses, kind of a train system running on wheels. That kind of system has now spread around the globe.

And it wasn’t just technology, Hoornweg says. Over the past three decades, from 2020 to 2050, a huge cultural shift has taken place.

Just one example: In Toronto, the sharing economy that started decades ago with Uber and Airbnb is everywhere now. “Sharing rides, sharing tools, sharing somebody to look after your dog when you’re not there.”

Yes, we apparently still have dogs in 2050.

In part, people are forced to share things; cars are scarce and homes are smaller. (Scores of home builders went belly-up in the 2030s when millions of people suddenly decided that big houses weren’t just expensive; they were lonely, too.)

But the scale of zero-carbon life also makes it easier to share. We’re living closer together and run into neighbors all the time. “We have more acquaintances — somebody we met in our ride pool or car pool or whatever,” Hoornweg says. “There’s no better way to [meet your neighbors] than sitting in a [shared] car and you can’t get away from them for 20 minutes or whatever.”

Some people hated losing their yards and their solitary commutes at first. Others loved the changes. Eventually, Hoornweg says, it just became normal. People stopped talking about it.

Life now goes on as it always did. But there’s one huge difference. We’re no longer heating up the planet.

A cow in Colombia enjoys some of the nutritious, fast-growing grass varieties developed at the International Center for Tropical Agriculture.

Dan Charles/NPR

Farmers Cut Down On Greenhouse Emissions (This Grass Really Is Greener)

2019: Jacobo Arango was traveling in a forested part of his country, Colombia, when he ran into one big reason for global warming. He didn’t see it, but he could hear it.

“You could hear the chainsaw cutting the forest; and the locals [were] telling us that this is nothing unusual for them, that they were hearing that every day,” says Arango, who is a researcher at the International Center for Tropical Agriculture, or CIAT.

This was totally illegal. But local farmers didn’t dare report it. “They said, if you do that, your life could be in danger,” Arango recalls.

Usually, what follows land clearing in the tropics is cattle grazing. It’s a careless, destructive form of cattle grazing, and Tim Searchinger, at the World Resources Institute, says it’s incredibly common. “Grazing land is about two-thirds of all agricultural land, and about a third of that came right out of clearing forests,” he says.

It’s a climate disaster. First, cutting down trees and tearing up forest soil releases huge amounts of carbon dioxide. Then, cattle release methane, a powerful greenhouse gas, as microbes in their stomach digest grass and leaves.

There are greenhouse emissions from other kinds of farming, too — from plowing and from fertilizer. Add it all up, and growing food accounts for a quarter of the entire climate change problem. That could increase, too, because billions of people around the world are getting richer; they want more beef, too.

“There is no solution to climate change that doesn’t dramatically reduce the land use demands and greenhouse emissions of agriculture,” Searchinger says.

He and his colleagues at WRI released a report last year that laid out a road map for how to do this. It includes lots of things, from wasting less food to reducing greenhouse emissions from fertilizer.

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Part of the seed collection at the International Center for Tropical Agriculture (CIAT), in Cali, Colombia. Scientists at CIAT used seeds like these to breed new, fast-growing grasses.

Dan Charles/NPR

But perhaps the single biggest piece of the solution is something we don’t often hear about.

Jacobo Arango wants to show it to me.

He’s brought me to a farm in the Patía valley, not far from Colombia’s Pacific coast.

This is cattle-grazing country. I see wide, grassy pastures, lined by trees. Nohely Angulo Mosquera, the leader of a farmers cooperative, is clapping his hands, calling his cows, inviting them to move to a new pasture.

This pasture is a bovine buffet. The grass is up to my waist. This is not ordinary grass that grows wild in this region. These are varieties with names like Mulato, and Cayman, which researchers at CIAT bred and selected to be top-quality cattle feed.

Angulo Mosquera says that these grasses grow so fast, and they’re so nutritious, he can keep four or even six cows on land that used to support just one. He does have to manage the cows more carefully; moving them every few weeks to new pastures when the grass is ready.

“More milk, more meat,” he says.

He doesn’t mention it, but it’s also true: In the old days, his cows took a long time to gain weight or produce a gallon of milk, but their gut microbes still kept churning out methane, day after day, year after year. Now, because the animals are growing so much faster, they aren’t releasing nearly as much methane per pound of milk or meat.

We’re looking at an essential part of a world without climate change.

And as we stand there, Jacobo Arango and I just start imagining it’s already happened, and talking as though it’s real.

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Nohely Angulo Mosquera is a leader of a farmers cooperative in the Patía valley, in Colombia.

Dan Charles/NPR

2050: The same way we stopped mining coal to generate electricity, we’ve stopped mining the soil to grow food.

“It’s different now, in 2050,” Arango says with a smile.

In a world without climate change, this is what cattle grazing looks like, all over the tropics. Farmers aren’t letting cows wander across the landscape in search of something to eat. They’re treating their pasture like a valuable crop, which it really is.

“This was critical, to change the mindset of cattle growers,” Arango says.

As a result, production is way up and “there is no need to cut the Amazon to do livestock production,” Arango says.

Another critical change: Americans are eating a lot less beef now — per person, half what they ate in 2020. “That’s a really, really big deal,” Searchinger says.

Traveling the country, you now see alternatives to beef and dairy products everywhere. There are blended mushroom-beef burgers in fast food chains and non-dairy cheese on pizzas. They even taste pretty good, thanks to the creative genius of America’s finest food scientists.

People who stop at these places don’t really think about the big global impact of what they’re doing, any more than they did when they were eating all hamburgers.

But they’ve been part of something amazing. It’s 2050 and there are almost 10 billion people in the world. They are eating better — yet the Amazon forest is still there. It hasn’t been sacrificed to grow food.

In fact, in parts of North and South America, including that farm we visited in Colombia, more trees are growing. We’re not mining the soil anymore. We’re replenishing it.

Methane in the atmosphere is surging, and that’s got scientists worried

Scientists love a good mystery. But it’s more fun when the future of humanity isn’t at stake.

This enigma involves methane, a potent greenhouse gas. Twenty years ago, the level of methane in the atmosphere stopped increasing, giving humanity a bit of a break when it came to slowing climate change. But the concentration started rising again in 2007 — and it’s been picking up the pace over the last four years, according to new research.

Scientists haven’t figured out the cause, but they say one thing is clear: This surge could imperil the Paris climate accord. That’s because many scenarios for meeting its goals assumed that methane would be falling by now, buying time to tackle the long-term challenge of reducing carbon dioxide emissions.

“I don’t want to run around and cry wolf all the time, but it is something that is very, very worrying,” said Euan Nisbet, an earth scientist at Royal Holloway, University of London, and lead author of a recent study reporting that the growth of atmospheric methane is accelerating.

Methane is produced when dead stuff breaks down without much oxygen around. In nature, it seeps out of waterlogged wetlands, peat bogs and sediments. Forest fires produce some too.

These days, however, human activities churn out about half of all methane emissions. Leaks from fossil fuel operations are a big source, as is agriculture — particularly raising cattle, which produce methane in their guts. Even the heaps of waste that rot in landfills produce the gas.

The atmosphere contains far less methane than carbon dioxide. But methane is so good at trapping heat that one ton of the gas causes 32 times as much warming as one ton of CO2 over the course of a century.

Molecule for molecule, methane “packs a bigger punch,” said Debra Wunch, an atmospheric physicist at the University of Toronto.

For 10,000 years, the concentration of methane in Earth’s atmosphere hovered below 750 parts per billion, or ppb. It began rising in the 19th century and continued to climb until the mid-1990s. Along the way, it caused up to one-third of the warming the planet has experienced since the onset of the Industrial Revolution.

Scientists thought methane levels might have reached a new equilibrium when they plateaued around 1,775 ppb, and that efforts to cut emissions could soon reverse the historic trend.

“The hope was that methane would be starting on its trajectory downwards now,” said Matt Rigby, an atmospheric scientist at the University of Bristol in England. “But we’ve seen quite the opposite: it’s been growing steadily for over a decade.”

That growth accelerated in 2014, pushing methane levels up beyond 1,850 ppb. Experts have no idea why.

“It’s just such a confusing picture,” Rigby said. “Everyone’s puzzled. We’re just puzzled.”

Scientists have come up with various explanations. Could it be growing emissions from fossil fuels or agriculture? An uptick in methane production in wetlands? Changes in the rate at which methane reacts with other chemicals in the atmosphere?

Nisbet and his team examined whether any of these hypotheses synced up with the changing chemical signature of methane in the atmosphere.

Some molecules of methane weigh more than others, because some atoms of carbon and hydrogen are heavier than others. And lately, the average weight of methane in the atmosphere has been getting lighter.

That seems to implicate biological sources such as wetlands and livestock, which tend to produce light methane. Daniel Jacob, an atmospheric chemist at Harvard who was not involved in Nisbet’s study, said that explanation squares with his own research. His results suggest most of the additional methane comes from the tropics, which are home to vast wetlands and a large proportion of the world’s cattle.

Estimates of emissions from coal mines and oil and gas wells suggest that fossil fuel contributions are rising too, but those sources usually release heavier molecules of methane, which would seem to conflict with the atmospheric observations.

Some researchers have proposed a way to resolve this discrepancy. Fires create an even heavier version of methane, and agricultural burning — particularly in developing countries — appears to have decreased over the last decade. A drop in in this source of ultra-heavy methane would make atmospheric methane lighter, on the whole, potentially masking an increase in emissions from fossil fuels.

Finally, reactions that break down methane eliminate more of the lighter molecules than the heavier ones. If that process has slowed down — causing methane to build up in the atmosphere — it would leave more light gas behind, possibly helping explain the overall trend.

Nisbet and his colleagues concluded they can’t rule out any of these explanations yet. “They might all be happening,” he said.

One possibility is conspicuously missing from the list. Scientists have long feared that thawing Arctic sediments and soils could release huge amounts of methane, but so far there’s no evidence of that, said Ed Dlugokencky, an atmospheric chemist at the National Oceanic and Atmospheric Administration who worked on the study, which will be published in the journal Global Biochemical Cycles.

Nisbet said he fears the rising methane levels could be a sign of a dangerous cycle: Climate change may cause wetlands to expand and allow the environment to support more livestock, leading to even more methane emissions.

“It clearly seems as if the warming is feeding the warming,” he said. “It’s almost as if the planet changed gears.”

If methane keeps increasing, the researchers say it could seriously endanger efforts to keep the planet’s temperature in check. Slashing CO2 emissions enough to meet climate targets is a tall order even without this extra methane.

“The unexpected and sustained current rise in methane may so greatly overwhelm all progress from other reduction efforts that the Paris Agreement will fail,” Nisbet and his co-authors wrote.

It doesn’t help that scientists recently revised the global warming potential of methane upward by 14 percent.

Regardless of what’s behind the recent increase, scientists say there are ways to reduce methane concentrations. And the benefits will accrue quickly because methane has a shorter lifetime than CO2, lingering in the atmosphere for only about a decade.

Humans account for as much as 60 percent of methane emissions, and nearly half of that may come from the fossil fuel industry, Jacob said.

One priority is to plug leaks from oil and gas wells, he said. Methane is the primary ingredient in natural gas, so companies have a financial incentive to try to capture as much as possible.

Often, a few culprits bear most of the blame, “which is both scary and a good thing,” because they represent big opportunities, Wunch said. At the Barnett Shale in Texas, 2 percent of the facilities produce half of the field’s methane emissions. In Southern California, the Aliso Canyon leak released roughly 100,000 tons of methane in 2015 and 2016 — the equivalent of burning 1 billion gallons of gasoline.

Scientists also have ideas for reducing methane emissions from livestock. Some experiments show that changing the diet of cattle by adding fats or seaweed, for instance, can reduce the amount of methane animals expel. Capping landfills and using the methane they produce for electricity would help too.

Measures like these could have a big impact, and Wunch said they give her reason to be hopeful.

“We could actually reduce the amount of methane in the atmosphere on timescales that are relevant to the problem we are facing right now,” she said.


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Climate change: Planet-warming power of cattle urine can be avoided by restoring farmland, study finds

Greenhouse gases from livestock can be cut by ensuring pastures are healthy, scientists say

Scientists have found restoring cattle pastures brings an unlikely environmental benefit by cutting the greenhouse gas emissions from cattle urine.

The planet-warming power of methane gas emitted by cows is well known, but their urine is also a contributor to climate change.

When the animals urinate on pastures, they produce the greenhouse gas nitrous oxide, which like methane has a far more powerful climate effect that CO2.

Previous research on the Somerset Levels in the UK has shown how adding cow urine to grassland stimulates gas production by adding nitrogen to the system and increasing soil water content.

In a new study, scientists investigated the levels of nitrous oxide coming from cow pastures across Latin America and the Caribbean after pouring samples of urine onto them.

They found that while the urine inevitably produced greenhouse gases, up to three times as much came from grassland that suffered from overgrazing and low soil quality.

With degraded land covering 150 million hectares of Latin America, this finding adds a further incentive to restore these pastures to their former quality.

“Degraded pastures are bad in so many ways,” said Dr Ngonidzashe Chirinda, a researcher at the International Centre for Tropical Agriculture and the study’s lead author.

“This study adds to the case for land restoration. Degraded pastures not only affect food security and the livelihood of farmers today, but affects the livelihood of future farmers because they emit more gases that cause global warming.”

Farm emissions are a major contributor to climate change, releasing CO2, methane and nitrous oxide that accounts for 10 per cent of emissions in the UK alone.

The new study was published in the journal Scientific Reports.