By Katherine Ellison for Hothouse.
Broadcast version by Suzanne Potter for California News Service reporting for the Solutions Journalism Network-Public News Service Collaboration
Twitchell Island, Sacramento County, California - Steve Deverel gazes out over a levee on the San Joaquin River to a buoy where half a dozen sea lions are barking. It's a loud reminder that even here, 50 miles inland, some of California's most productive farmland lies perilously close to the Pacific Ocean. At any moment, a weak spot in the more than 1,000 miles of earthen levees protecting islands in the Sacramento-San Joaquin River Delta could unleash a salty deluge, threatening not just crops, but the drinking water for as many as 27 million Californians.
Deverel, a Davis-based hydrologist, refers to this threat as "The Big Gulp," a breach that would suck in tens of billions of gallons of river water, drawing ocean water in its wake. All it would take is some heavy rain, a moderate earthquake, or even hard-working gophers tunneling through earthen barriers first built in the late 1800s.
It wouldn't be the first time such a disaster happened.
On a sunny day in June 1972, a levee failed without warning or apparent cause near Andrus Island, about an hour's drive from San Francisco. Water ran four feet deep over the farmland. Thirty-foot cruisers and houseboats smashed against the embankments. Hundreds of homeowners fled rising waters, with several people seriously injured. In 2004-on another calm, sunny day-it happened again. This time the water turned 12,000 acres of prime California farmland into a brackish lake, costing $100 million in damages.
Deverel now hopes to save the Delta by flooding it before the Pacific can. And he wants to pay for it with carbon credits.
"Carbon-farming" in the wetlands
Deverel, 70, has spent three decades trying to head off the Big Gulp. Climate change is his chance. His project, funded to date by California state agencies and the University of California, has so far inundated 1,700 acres of Delta farmland on Twitchell and nearby Sherman island, transforming them into marshes of cattails and tule reeds. Each year, new plants growing in these restored wetlands will suck carbon dioxide (CO₂)-the most abundant greenhouse gas-out of the atmosphere, storing it in strata of accumulating muck that will help buttress the dikes in danger of collapsing.
The project passed its first important milestone on October 27, 2020, when the American Carbon Registry issued credits for 52,000 tons of CO₂ removed by the experiment, which is still in its very early stage. That makes this the first wetland project (and only one so far) to generate verified carbon credits in the US, according to Steve Crooks, a Sausalito, California-based wetlands scientist and global expert in the field of "carbon-farming" from coastal wetlands.
The Delta project is also one of very few such efforts around the world, yet its promise is enormous.
Even as they cover just 9% of the Earth's surface, wetlands are the largest natural carbon sink on land, sequestering an estimated 35% of the world's carbon stored on land, more than all other biomes combined. Since a majority of wetlands are degraded or destroyed, environmental scientists see restoring them as a huge potential source of carbon credits as countries and corporations ramp up their commitments to cut greenhouse gas emissions. Rehabilitating the earth's wetlands would provide myriad benefits in addition to carbon sequestration, possibly even more environmentally useful than carbon projects in forestry.
Yet managing these landscapes is a lot more complicated-and expensive-than simply flooding fields or replanting trees. Deverel believes the Delta project has revealed a path forward. The key is a rich, brown crumbly soil known as peat.
The promise of peat
A few thousand years after the end of the last Ice Age, the Delta was covered by a marshy, freshwater inland sea. Over millennia, layers of moss, mud, and vegetation accumulated to form peat. Under the right conditions, peatlands can store vast amounts of carbon. Marshes "sequester" or store CO₂ through photosynthesis as they grow, and the carbon stays trapped in the plants as they die and decompose underwater. Once drained, however, peat can be fabulous for growing crops, as farmers who came here after the Gold Rush soon discovered. The farmers, known as "swamplanders," hired Chinese laborers to build the levees and drain the marshes, and planted rows and rows of corn and alfalfa, much later adding other crops, including wine grapes, walnut and almond trees, cotton, sugar beets, and blueberries.
More than a century would pass before scientists realized the farmers were harvesting their own ruin.
The problem is known as "subsidence," a gentle word for a sinister situation. When peat dries, it oxidizes and evaporates, or is swept away by the wind, steadily robbing the Delta islands of about an inch in height each year. As they shrink in volume, the islands provide less and less of a buffer against the water pressure on the aging levees.
Subsidence explains why you can stand on a grassy field here, some 300 feet from the levees' edge, and look up to watch ships passing on the river. Some parts of Twitchell and other Delta islands are now more than 20 feet below sea level. Subsidence, and the growing pressure on the levees, also explain why there's more to the threat than the specter of water someday coursing over the levees. In some areas it's already seeping under them, says Deverel. That's forcing farmers to fortify old embankments while continually draining their land.
There's also a broader threat. Soggy peatlands can be powerful carbon sinks. All that changes when the peat dries out. As peat oxidizes, it releases stored CO₂. In the Delta, this translates to an area of about 150,000 acres of soil turned into "this weird little chimney in the middle of the state that is just pumping out carbon dioxide," says Campbell Ingram, executive director of the Delta Conservancy, a state agency that is collaborating with Deverel on the carbon-credits project.
Over more than 30 years of careful measurements, Deverel has found that each year, on average, each of those acres of dried-peat farmland emits roughly ten tons of CO₂, roughly equivalent to the annual emissions of 217,000 gas-powered cars.
Deverel, Ingram, and their colleagues see this as an opportunity.
Inundating the land, and allowing the ancient bulrushes and cattails to return-or potentially cultivating rice-would stop those emissions immediately, and even store carbon as new plants grow. Deverel and Ingram hope the process could start to reverse the subsidence by adding as much as two inches of soil a year as watery plants die and form new peat. "It's slow, yes-it could take 150 years to get back to sea-level," says Ingram. "But every added foot reduces the pressure on the levees."
Restoring Delta wetlands would have many other benefits as well. Healthy wetlands help filter freshwater, offer habitat for wildlife, and provide a buffer for flood control-all services increasingly in demand as climate change brings more devastating droughts and rising sea levels. In this way, the Delta project could shift the carbon credits paradigm, using the credits not only to reduce or "mitigate" greenhouse gas emissions but to help adapt to the inevitable results of climate change in coming years.
"This project is still in its early stages but we're very hopeful about what it implies for California's sustainability," says Michelle Passero, director of climate and nature-based solutions for The Nature Conservancy. The international non-profit, which owns an entire Delta island, has recently begun working with Deverel to greatly expand the scope of his plan, converting 4,000 acres from corn to rice and another 1,000 to restore wetlands habitat. Passero says they hope to generate carbon credits from the project within the next few years, providing income to pay for more restoration, and ideally creating a model for others to follow.
To do so, however, the Delta's defenders still need to overcome three daunting obstacles: the science, the expense, and the politics of wetlands conversion.
The Devil's in the data
In the first US attempt to farm carbon in US wetlands, the scientific calculations didn't add up.
In December 2013, Tierra Resources, a small environmental restoration firm based in New Orleans, announced that the American Carbon Registry had approved its "revolutionary new tool:" a "first of its kind" methodology to restore degraded wetlands in the Gulf of Mexico.
Seven years later, however, the company quietly canceled its pilot project in a Louisiana swamp. The problem was "high uncertainty with the data," wrote Tierra Resources CEO Sarah Mack in an email. The ACR requires periodic monitoring reports, meaning carbon farmers must continually prove they're doing what they initially promised.
Mack, who later consulted on the California Delta project, praised Deverel and colleagues for what she described as their pioneering work. "They showed it can be done," she said, "and that is going to encourage other scientists to follow them."
As Mack acknowledged, the Delta project has had some key advantages over her own effort. For one thing, after three decades of studying and measuring emissions from the land, Deverel has more scientific certainty. But more important is the problem of methane, a greenhouse gas that is about 25 times more powerful than CO2.
All wetlands emit methane, as anaerobic soil microbes digest growing plants. But Mack's wetlands in the Gulf of Mexico lacked the key ingredient of peat. In peat wetlands, inundating the land-and stopping up those weird little chimneys-has the potential to reduce so much CO2 that it would more than compensate for new methane emissions, according to Deverel.
Peat's promise is already inspiring some mega-projects in swamp forests, bogs, and fens, many thousands of miles away from the Delta. In Indonesia, the Katingan Metaya Project claims it is generating 7.5 million carbon credits per year from peat-rich forests, avoiding emissions equal to those of France. In Scotland, a fast-fashion billionaire is working on a project to farm carbon from peatlands on his extensive landholdings. Closer to home, in North Carolina, scientists have investigated the potential for a carbon farm on 10,000 acres of previously drained pocosins, wetland bogs with woody shrubs and sandy peat soil.
The clock is ticking. As peatlands increasingly dry out, those "weird little chimneys" are popping up all over the planet, potentially creating a dangerous feedback loop for climate change. That makes it all the more important that the Delta defenders find answers to the economic and political challenges of wetlands restoration.
Show me the money
Wetlands restoration is expensive, and the Delta carbon project is no exception. Over the past 12 years, California state agencies have spent nearly $17 million restoring and managing wetlands in the project area, according to Bryan Brock, an engineer for the California Department of Water Resources (DWR). That bill would have been much larger had the land not already been owned by DWR. Another $1.5 million was spent on research-related expenses, including 10 eddy covariance stations, which can cost $50,000 each, to measure gas flows and temperature changes over the wetlands.
Now, the biggest hurdle is making the project financially sustainable. For all its expense, the project has yet to produce any revenue. Carbon credits issued so far have gone to the project landowner, DWR, which can't sell the credits due to rules forbidding profits from publicly funded projects, as Brock explains.
To finance more wetlands restoration, the Delta team must do the political work of convincing thousands of farmers to convert at least some of their land from profitable crops to marshes or rice, and then keep them that way for a minimum of 40 years. Carbon prices have been rising, but at less than $10/ton for the voluntary market, are still far from enough to change a lot of minds.
"It's a bit ridiculous," is how Bruce Blodgett, executive director of the San Joaquin Farm Bureau Federation, characterizes the Delta carbon-farming proposal. "Are we supposed to buy our seeds with carbon credits?"
Blodgett worries the state will step in and force farmers to participate. He insists the Delta farmers are doing just fine dealing with subsidence by paying property taxes to fund work on the levees and, as long as the water keeps flowing, he doesn't want to change. "We have one area in the entire state of California that we know we can still be farming 150 years from now," he says, "and they want to plant tules there."
Yet Mother Nature increasingly has put her finger on the scales. As sea levels rise, that salty water seeping under the levees is already threatening crops, while farmers must pay more to keep draining their land. The increasing threats from climate change may also eventually move governments to act more aggressively, which could raise the price of carbon credits and provide another inducement for the farmers. "If we get to $100 a ton, that solves the problem," says Deverel.
In the meantime, he continues with his research and plans for the next phase of the project, on The Nature Conservancy land, continuing with the work that has now consumed more than half of his life. Progress so far has been small and slow, and maybe even a little nerve-wracking if you're the sort who tends to doom-scroll climate news.
But Deverel isn't one for doom-scrolling. "This is what I am called to do now," he says. "I don't need to worry about the entire stairway, just the next step."
Katherine Ellison wrote this article for Hothouse.
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Michigan's electric vehicle industry is praising the Biden administration for its latest investments in EV manufacturing and innovation.
About $650 million will go toward retooling auto plants in Lansing and Marysville to produce newer EV models. The funding is part of the Inflation Reduction Act, going to Michigan and seven other states to make more EVs.
Sophia Schuster, policy principal for the Michigan Energy Innovation Business Council, said the money should help the state fight "brain drain." She noted Michigan is 49th in the U.S. in population growth since 1990.
"I think it's exciting to show that investments like these not only encourage people to stay and come in (to) Michigan but that there is a lot of potential for the clean energy workforce," Schuster explained. "Particularly in the auto manufacturing space."
In Michigan, the plans are expected to retain more than 1,000 jobs and create a few dozen new ones. Billions of dollars have already been spent during the Biden administration to reduce vehicle emissions and combat climate change. Transportation is the top source of emissions in the U.S.
Jane McCurry, executive director of the trade group Clean Fuels Michigan, said it is an exciting time to be in the renewable energy industry. Public and private dollars are also pouring into EV chargers, zero-emission school buses and other alternative mobility sources. She argued it will ultimately give consumers more choices.
"No matter what your choice is, you know that you can fuel it in your community, on your commute, on your way up north for vacation," McCurry emphasized. "That is where public dollars come in, is making sure that people can get everywhere they need and want to go within Michigan in a safe, efficient, effective, enjoyable way."
Gov. Gretchen Whitmer has set a statewide goal of building 100,000 EV chargers in the state by 2030, enough to support 2 million vehicles.
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A new study by the University of Illinois Urbana-Champaign suggests the long-term effects of climate change could create a higher risk of extinction for certain bird species.
Between 1980 and 2015, researchers studied more than 400 general and specialist bird species across North America. While a general species can thrive in various environments, specialist birds can only live in specific conditions.
Madhu Khanna, professor of environmental economics at the university, said the data show climate change affects migratory birds and specialist birds at greater rates than the general bird population.
"What we found is that an increase in the number of days that were hotter than 25 degrees centigrade decreased the population of birds, as well as the number of species, by about 2% or so," Khanna outlined.
Khanna pointed out specialist birds lost 7% to 16% of their populations because of climate change. She added other factors were already affecting birds, including pesticides, land use change and habitat loss. Researchers compared climate data for the same period alongside the studies.
The report found general species, like the North American sparrow, declined by almost 3% during the 25-year study. The threatened spotted owl and red-cockaded woodpecker, both specialist species, declined by 5%.
Khanna added they studied other variables that might influence birds' ability to adapt to climate change.
"Were there any changes that they might be doing in terms of their migratory routes or anything else because of this, that might reduce the negative impact of the changing climate? And we actually found no such effect," Khanna emphasized.
Khanna believes although birds are currently adapting to their respective environments, she is alarmed about the long-term effects on them if climate change continues. The Illinois Department of Natural Resources has recorded a total of 458 bird species in the state.
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By Stephen Battersby for the Proceedings of the National Academy of Sciences.
Broadcast version by Kathryn Carley for Commonwealth News Service, reporting for the Pulitzer Center-Public News Service Collaboration.
As a phrase and as a promise, net zero has been a great success. Hundreds of countries have pledged to reduce their net greenhouse gas emissions to zero by around the middle of this century. So, too, have thousands of regions, cities, and companies. Net zero has become a beacon of hope, guiding us to climate safety.
But look closely, and the beacon becomes a little blurry. Some scientists argue that net zero might lead us to rely too heavily on technologies that capture CO2 from the air. That could bring dangerous delays and unwelcome side effects, and give fossil fuel producers leeway to keep pumping and polluting. And its allure may be obscuring our need to look beyond net zero to a more ambitious goal-a world of net-negative emissions.
Some climate scientists have ideas about how we could refine net zero to make it a more focused and effective target. Others say it should only be one part of a new climate narrative. "We don't think enough about net zero, what it means, and if it's the right goal," says environmental social scientist Holly Jean Buck, of the University at Buffalo in New York.
With the fate of the planet riding on the outcome, it's vital that governments and institutions are not led astray by their climate beacon-so the debate over net zero is more urgent than ever.
The Root of Zero
The idea of net zero is firmly based on climate science. In the 2000s, scientists worked out that if we stop pouring CO2 into the atmosphere, global average temperatures should roughly stabilize. That is because two effects of Earth's oceans happen to cancel out. Today, the atmosphere is kept relatively cool by the oceans. As seawater slowly warms, we lose that cooling effect, so if emissions fall to zero, we might expect the atmosphere to carry on warming for a few decades-a phenomenon known as thermal inertia. But the oceans also keep absorbing CO2, which should roughly balance the thermal inertia and keep temperatures steady.
Net zero took off in 2018, driven by the United Nations report "Global Warming of 1.5 °C." Three years earlier, the Paris Agreement had set out a goal to limit warming to well below 2 °C above pre-industrial levels and pursue efforts to limit it to 1.5 °C. The new report laid out how the world might try to hit the more ambitious end of that goal, based on models that combine climate and economic activity. It concluded that to avoid warming of more than 1.5 °C, we would not only have to cut emissions deeply, but also remove a lot of CO2 from the atmosphere. Such removal could balance any stubborn, ongoing sources of greenhouse gases, known as residual emissions. These might include CO2 from concrete manufacture, for example, or nitrous oxide from fertilizers. So instead of absolute zero emissions, the new goal aimed for net zero, which allows some residuals to be balanced by removal.
This was only possible because technologies that remove CO2 from the air had become feasible. "Targets through the years have tended to reflect the practicality at the time of reducing emissions," says climate ecologist Stephen Pacala at Princeton University in New Jersey. "When you could envision a practical path to zero net emissions without leaving the world in poverty-all of a sudden, humanity jumped on net zero as a target."
It has undoubtedly had a galvanizing effect. "Before this, few companies had climate targets at all," says Sam Fankhauser, a climate economist at the University of Oxford in the UK. "So this is a step in the right direction."
But that shouldn't be the end of the story. "Net zero comes from the science, so it's subject to change as we learn more," says climate economist Sabine Fuss at the Mercator Research Institute on Global Commons and Climate Change in Berlin, who was a lead author on the "Global Warming of 1.5 °C" report. Climate scientists agree that the concept holds several crucial ambiguities that need to be resolved.
Zero Sum
For a start, what is the best balance between cutting emissions and removing CO2? That depends on which emission sources will be too difficult to cut. But when Buck and her colleagues analyzed 50 national long-term climate strategies, they found that countries are inconsistent in how they consider residual emissions. "The risk is that governments put things that are expensive or politically inconvenient to abate into the 'residual box,'" the paper states. That makes it hard to know how much CO2 removal we need.
According to these strategies, the average residual emissions in developed countries will be 18% of current total emissions at the time of net zero. Extended to the whole world, that would imply annual removals of at least 12 billion tonnes of CO2.
Natural solutions, such as planting forests, can't come close to reaching this quantity on their own-and in a warming world, they will be increasingly vulnerable to fire, disease, and chain saws. So the assumption is that we will use a range of novel removal methods: using machines to suck CO2 directly from the atmosphere, for example, or burning biomass to generate energy while capturing and storing the CO2 emitted.
Most of these technologies operate at small scales today, collectively removing only about two million tonnes of CO2 per year. For now, most of them are expensive to operate. Some need a lot more research and development and may yet prove difficult to scale up. That's the first problem with asking too much of carbon removal: It might not have the capacity to meet such high demand, and then we would fail to hit net zero.
The second problem is unwanted side effects. Deployed at large scale, biomass-based CO2 removal could compete for land with agriculture or with rich ecosystems, which could push up global food prices or harm biodiversity. Other approaches are also likely to have snags, especially if stretched too far. Direct air capture requires a lot of energy, which must come from a very-low-carbon source not to be counterproductive. Enhanced weathering, which involves grinding certain types of rock to speed natural CO2-absorbing chemical reactions, could create air pollution.
Without defining the levels of reductions and removals that lead to net zero, there's no clear imperative for each country or company to cut its emissions to the bone. Instead, they might hope to pay others to remove lots of CO2 on their behalf. "Everyone thinks they will buy negative emissions from someone else," says climate scientist Bas van Ruijven at the International Institute for Advanced Systems Analysis in Laxenburg, Austria.
Worse, it seems increasingly likely that CO2 removal will have to go beyond merely balancing residuals. "Now it looks like we will need net negative to meet the Paris goal," says Fuss. That means removing more CO2 from the atmosphere than we put in. Researchers in the international ENGAGE project have developed models that include a range of sociopolitical constraints, such as the ability of governments to enforce climate legislation. These models project that climate warming will overshoot the 1.5 °C target by 2050. Reversing that overshoot would require several hundred gigatonnes of CO2 removal during this century. "So you cannot have an enormous amount of residual emission, as then you need an even more enormous amount of carbon removal," says van Ruijven, who is a member of the ENGAGE project.
It may be wise to go further and try to repair some of the damage we have done, dialing down global temperatures closer to pre-industrial levels and curbing the ocean acidification caused by absorbed CO2. That would, of course, require even more removals. Despite this, companies and countries are not yet planning to reach net negative.
In some quarters, net zero is seen as a final goal. This could leave the door open for fossil-fuel production to continue at high levels and for new infrastructure that could commit us to burning those fuels for decades to come. "We haven't focused enough on the phaseout of fossil fuels," says Buck. "If we only focus on emission at the point of combustion, then we are missing half the picture." The 2023 UN Climate Change Conference (known as COP28) alluded to this problem, calling for "transitioning away from fossil fuels in energy systems." But, this falls far short of a phaseout. "It is promising that they said something, but it could have been stronger," says Buck. "What you need is a plan and a lot of resources committed to phaseout."
Zero Clarity
Net zero holds a host of other ambiguities. "Today, everybody has their own idea of what net zero means," says Fuss. "So we should take a step back and refine the concept. It is really important to get all these things straight, so we are not fooling ourselves."
For example, it's unclear whether net zero should include climate feedback effects, such as CO
2 emitted by thawing permafrost. These could require vastly more removals to prevent temperatures from rising.
Nor does the target emphasize urgency. If governments are aiming for net zero in 2050, they might feel free to kick their heels for a while. But many mitigation measures will need decades to scale up, so "it's vital to reduce emission as much as possible in the short-term," says Fuss. "You don't break something just to then repair it."
Net zero doesn't yet specify the durability of removals, either. Today's emissions will linger for centuries, so they can't simply be balanced by a form of removal that is likely to last only years or even decades. As Fankhauser et al. write: "Achieving net zero through an unsustainable combination of fossil-fuel emissions and short-term removals is ultimately pointless."
The sum should also explicitly include any knock-on effects. For example, planting forests at high latitudes can be counterproductive because they create a darker landscape that absorbs more solar heat, melting local ice and snow.
Then there is the question of whether to include other greenhouse gases, such as methane, in the net-zero sum. Methane has a much shorter lifetime in the atmosphere, so attempting to cancel out methane emissions with CO
2 removal would tend to mean more warming in the short term, and less in the long run. That could be good or bad, depending on whether it takes us past climate tipping points.
Zooming in on Zero
How can we do better? The first thing is to decide what should be classed as a residual. "We should make sure that residual emissions are truly hard to abate," says Buck. Voluntary codes are starting to address that, including the net-zero corporate standard launched by the Science Based Targets initiative, which calls for residuals to be only 5-10% of a company's current emissions.
To get removals moving, Fuss thinks that we need higher prices on carbon emissions. "If we are asking people to remove, we are asking them to perform a public service," she says, "so we should be compensating them for extracting each tonne of CO
2."
Carbon pricing could also curb fossil fuel production. Pacala led a 2023 National Academies report on accelerating decarbonization, which, among other things, recommended an economy-wide carbon tax in the United States. He says that the 2022 Inflation Reduction Act (the nation's main policy tool for moving toward net zero) omitted any such tax in order to gain political traction.
Assuming that carbon removals can scale up fast enough, it will be vital to prove how much CO
2 they are removing, through monitoring, reporting, and verification (MRV) systems. That could be challenging. "MRV is hard enough with forests, where we already have decades of experience," says Buck. "With novel techniques, it's a big challenge, and I'm not sure it's solvable on a timescale of 20 years or so." But there are some promising signs. In November 2023, the European Parliament voted to adopt a new certification scheme for removals, aiming to boost their credibility and scale. Meanwhile, advances in remote sensing and machine learning could make MRV more achievable.
As well as trying to redefine net zero, perhaps nations and societies also need to take a step back and think more broadly about what to strive for. Buck thinks that net zero should become just one among a set of targets, including reductions in fossil-fuel production and enhancing the capacity of countries to implement the clean-energy transition. She also considers the term to be fundamentally unsatisfying, a piece of accountancy that is not compelling to most people. Perhaps the world needs a more inspiring climate narrative that comes not just from scientists, but also other groups. "We need to evolve broader languages," Buck says, "and make more effort to understand what would encourage people to change their lifestyles and consumption."
Fankhauser, meanwhile, cautions against focusing on climate impacts alone. "The risk is that we maximize natural systems for carbon uptake but compromise biodiversity and other ecosystem services," he says. "We need a holistic point of view."
Climate solutions should also avoid dumping pollution or costs disproportionately on disadvantaged communities. This isn't just a moral matter. "People are not going to go along with these changes unless they see benefits in their own lives," says Pacala, who points to the plight of coal miners in the United States and other workers whose jobs may be threatened by the energy transformation. "We have to manage the jobs of legacy workers, who were previously thrown under the bus," he says.
At the moment, there is no pithy phrase to sum up these diverse aims. "Net zero is powerful because it is two words," says Fankhauser. Adding more detail could spoil that rhetorical impact. Low-residual, urgent, all-greenhouse-gas net zero, aligned with biodiversity and poverty reduction-it hardly trips off the tongue. For now, at least, researchers and policymakers may have to stick with those two words, while carefully contemplating all the things that add up to zero.
Stephen Battersby wrote this article for the Proceedings of the National Academy of Sciences.
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