Climate

SAN FRANCISCO — Several Antarctic glaciers are undergoing dramatic acceleration and ice loss. Hektoria Glacier, the worst affected, has quadrupled its sliding speed and lost 25 kilometers of ice off its front in just 16 months, scientists say.

The rapid retreat “is really unheard of,” says Mathieu Morlighem, a glaciologist at Dartmouth College who was not part of the team reporting these findings.

The collapse was triggered by unusually warm ocean temperatures, which caused sea ice to retreat. This allowed a series of large waves to hit a section of coastline that is normally shielded from them. “What we’re seeing here is an indication of what could happen elsewhere” in Antarctica, says Naomi Ochwat, a glaciologist at the University of Colorado Boulder who presented the findings December 11 at the American Geophysical Union meeting.

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Hektoria Glacier, Green Glacier, and Crane Glacier sit near the tip of the Antarctic Peninsula, which reaches up toward South America. The crescent moon–shaped bay, called the Larsen B Embayment, once seemed stable. As these glaciers oozed off the coastline, their ice used to merge into a floating slab around 200 meters thick. This slab, called the Larsen B Ice Shelf, was about the size of Rhode Island and filled the entire bay.

Having existed for over 10,000 years, this ice shelf buttressed and stabilized the glaciers flowing into it. But during a warm summer in 2002, it suddenly fragmented into thousands of skinny icebergs (SN: 3/27/02).

Hektoria, Green, and Crane glaciers — no longer contained by the ice shelf —  began to flow into the ocean several times faster than they had before, shedding billions of tons of ice over the next decade.

Then starting in 2011, the hemorrhaging slowed down. The thin veneer of sea ice that forms over the bay each winter began to persist year round, preserved by a series of cold summers. This “landfast ice,” attached firmly to the coastline, grew five to 10 meters thick, stabilizing the glaciers. Their floating tongues gradually advanced back into the bay. But things changed abruptly in early 2022. On January 19 and 20, the landfast ice disintegrated into fragments, which drifted away.

Satellite images taken just 10 days apart reveal the dramatic breakup of sea ice in Antarctica’s Larsen B Embayment. On January 16, 2022, sea ice filled the bay (left). By January 26 (right), the ice had fractured and was drifting away following a series of powerful waves that struck the bay several days earlier. Left: Joshua Stevens, MODIS/LANCE/EOSDIS/NASA, WORLDVIEW/GIBS/NASARight: Joshua Stevens, MODIS/LANCE/EOSDIS/NASA, WORLDVIEW/GIBS/NASA

Using data from ocean buoys farther north, Ochwat and colleagues determined that a series of powerful waves, higher than 1.5 meters, had swept in from the northeast — cracking apart the landfast ice. Those waves were highly unusual for this area.

The Southern Ocean, which encircles Antarctica, holds some of the world’s roughest waters. The Antarctic Peninsula extends up into this turbulent region, but its east side, where the Larsen B Embayment sits, rarely feels the waves. It is normally protected by several hundred kilometers of pack ice — floes of sea ice, pressed together by ocean currents — that dampen the waves, leaving the waters near Larsen as flat as a mirror.

In 2022, water temperatures near the surface of the Southern Ocean rose several tenths of a degree Celsius higher than normal, causing pack ice to shrink and peel away from the peninsula. This exposed the area to waves, which then broke up the landfast sea ice.

The glaciers accelerated as their floating tongues, no longer held in place, fragmented into bergs. Crane Glacier lost 11 kilometers of ice, nearly erasing its floating tongue; Green Glacier lost 18 kilometers, encompassing all of its floating ice.

Hektoria lost all 15 kilometers of its floating ice — followed by another 10 kilometers of ice that is normally more stable, because it rests on the seafloor. That “is faster than any tidewater glacier retreat that we know of,” Ochwat says.

The previous standout, Alaska’s Columbia Glacier, had lost 20 kilometers of ice in 30 years, records show. But Hektoria lost its 10 kilometers of nonfloating ice in just five months — including 2.5 kilometers that crumbled in a 3-day period.

All of this suggests that people trying to predict sea level rise need to consider sea ice, Morlighem says. Up until now, “its role in [glacier] dynamics has been completely ignored.”

Ochwat is waiting to see what will happen as the current Antarctic summer heats up between December and March. Hektoria and the other glaciers have been retreating only during summer months, when sea ice is absent; they pause during winter, when the surface of the bay freezes for a few months.

If Antarctic sea ice continues to shrink, as it has since 2022, it could spell trouble, says study coauthor Ted Scambos, a glaciologist also at UC Boulder. “You’re going to have a longer section of coastline where wave action can act on the front of ice shelves and glaciers,” potentially accelerating glacial retreat. More

Days of contentious wrangling in Dubai at the United Nations’ 28th annual climate summit ended December 13 with a historic agreement to “transition away” from fossil fuels and accelerate climate action over the next decade. The organization touted the agreement as a moment of global solidarity, marking “the beginning of the end” of the fossil fuel era.

But the final agreement reached at COP28, signed by nearly 200 nations, did not include language that explicitly mandated phasing out fossil fuel energy, deeply frustrating many nations as well as climate scientists and activists.

The agreement is considered the world’s first “global stocktake,” an inventory of climate actions and progress made since the 2015 Paris Agreement to limit global warming to “well below” 2 degrees Celsius above the preindustrial average (SN: 12/12/15).

It acknowledges the conclusions of scientific research that greenhouse gas emissions will need to be cut by 43 percent by 2030 compared with 2019 levels, in order to limit global warming to 1.5 degrees Celsius by the end of the century. It then calls on nations to speed up climate actions before 2030 so as to reach global net zero by 2050 — in which greenhouse gases entering the atmosphere are balanced by their removal from the atmosphere. Among the actions called for are increasing global renewable energy generation, phasing down coal power and phasing out fossil fuel subsidies.

But among many scientists gathered in San Francisco at the American Geophysical Union’s annual meeting to discuss climate change’s impacts to Earth’s atmosphere, polar regions, oceans and biosphere, the reaction to the language in the agreement was more frustrated than celebratory.

“The beginning of the end? I wish it was the middle of the end,” says climate scientist Luke Parsons of the Nature Conservancy, who is based in Durham, N.C. “But you have to start somewhere, I guess.”

It is a step forward, says Ted Scambos, a glaciologist at the University of Colorado Boulder. “Saying it out loud, that we are aiming to phase out fossil fuels, is huge.”

It’s not a moment too soon: The globe is already experiencing many climate change–linked extreme weather events, including the hottest 12 months ever recorded (SN: 11/9/23). Still, Scambos says, “it’s a tribute to the science and the negotiators that we can take this step now, before the disastrous global impacts truly get underway.” But, he added, “I fear that the pace [of future climate action] will … still be driven by impacts arriving at our collective doors.”

Other researchers had a grimmer take.

“It was weak sauce,” says climate scientist Michael Mann of the University of Pennsylvania. “What we really need is a commitment to phase out fossil fuels, on a very specific timeline: We’re going to reduce carbon emissions by 50 percent this decade, bring them down to zero mid-century. Instead, they agreed to transition away from fossil fuels — the analogy that I use is, you’re diagnosed with diabetes, and you tell your doctor you’re going to transition away from doughnuts. That’s not going to cut it. It didn’t meet the moment.”

Eric Rignot, a glaciologist at the University of California, Irvine, called the agreement “deeply disappointing and misleading,” noting that it didn’t include any language specifically calling for phasing out fossil fuels. Furthermore, he says, “COP28 keeps entertaining the idea that 1.5 degrees Celsius may be achievable, but everyone is offtrack to meet that goal. [And] for ice sheets and glaciers, even 1.5 degrees is not sustainable.”  There already are fears, for instance, that the melting of Greenland’s ice sheet can’t be stopped (SN: 8/9/21).

Even if the world stays close to that average temperature, “the ice sheets are going to be retreating,” says Rob DeConto, a glaciologist at the University of Massachusetts at Amherst. “But you start getting out toward the end of the century, and all hell is going to break loose if we go much above 1.5. You’re talking about actually exceeding the limits of adaptation around so much of our coastlines.”  

On December 12, the eighth anniversary of the signing of the Paris Agreement, the European Union’s Copernicus Climate Change Service noted that the world has, in effect, “lost” 19 years by delaying action to reduce fossil fuel emissions. Back in 2015, climate projections suggested that Earth’s average temperature would reach the 1.5 degrees C threshold by the year 2045 — then 30 years away. Now, projections show that the planet may reach that benchmark by 2034, just 11 years in the future.

“We’ve got a shrinking window of opportunity,” Mann says. “And that window of opportunity will close if we don’t make dramatic and immediate reductions to our carbon emissions.” More

This year’s United Nations’ annual climate summit, dubbed COP28, is making a lot of headlines — not something I would have found myself writing a few years ago.

One reason for COP’s higher profile is a growing sense of urgency to take stronger action to reduce humans’ fossil fuel emissions and mitigate the looming climate crisis. The world is nowhere near on track to meet the goals of the 2015 Paris Agreement — that is, reducing greenhouse gas emissions sufficiently to limit global warming to “well below” 2 degrees Celsius of preindustrial averages by the year 2100 (SN: 12/12/15). Meanwhile, 2023 has been the hottest year on record, people have been suffering through a barrage of extreme weather events, including heat waves, droughts and floods, and 2024 is likely to break more temperature records (SN: 12/6/23; SN: 7/19/23).

The headlines emerging from COP28 have been a mix of pleasing, frustrating and bewildering. For example: It’s good news that 198 nations have ratified the Loss and Damage Fund, a formal acknowledgment by wealthy, high-polluting nations that they should help mitigate the rising costs of climate change faced by developing nations. But it’s frustrating that the pledges by the wealthy nations so far amount to just about $725 million, less than 0.2 percent of the annual climate change–linked losses faced by developing nations.

For me, one of the biggest questions related to those headlines pertains to methane. It feels unclear whether, on balance, there’s more good or bad news when it comes to emissions of that second most important human-caused greenhouse gas.

Methane is a powerhouse climate-warming gas, with about 80 times the atmosphere-warming potential of carbon dioxide. However, methane has a saving grace: It mercifully lingers for only about a decade in the atmosphere (SN: 4/22/20). Carbon dioxide can stick around for up to 1,000 years. Cutting methane emissions can mean its atmospheric concentration drops relatively rapidly.

The Global Methane Pledge, launched two years ago at COP26, may be gaining some momentum, but it still lacks the sign-on of key big-emitting nations. Then there’s the December 1 announcement by 49 oil and gas companies that they would reduce methane leaks from their infrastructure to “near zero” by 2030, which seems like a good thing on the face of it but has also been called greenwashing (SN: 11/24/21).

And all of this policy wrangling is happening against a bizarre backdrop: a startling, puzzling, worrisome sharp increase in methane emissions over the last decade — not from humans, but from natural sources, particularly wetlands.

To help me sift through the headlines and better understand all the news that’s seeping out, I talked with Euan Nisbet, a geochemist at Royal Holloway, University of London in Egham.

Methane “is rising very fast,” Nisbet says. “So fast it looks like the Paris Agreement is going to fail.”

Countries are promising to cut methane emissions

While the rise in natural methane emissions is worrisome, about 60 percent of current methane emissions into the atmosphere still comes from human activities. Methane doesn’t just seep out of leaky oil and gas pipelines or get pumped into the air during coal combustion. Agriculture, including ruminant animals, are a big source (SN: 5/5/22). Landfills are another (SN: 11/14/19).

That’s where the Global Methane Pledge comes in, promising a 30 percent cut in humans’ emissions by 2030. The pledge was spearheaded in 2021 by the United States and the European Union, and so far, 150 nations have signed on. Most recently, Turkmenistan, which has sizable methane emissions, joined. So there’s hope: If everyone were to follow suit, it really is possible to cut global methane emissions deeply, bringing us much closer to meeting the Paris Agreement’s goals, Nisbet argues in a Dec. 8 editorial in Science.

Still, many of the world’s biggest methane emitters, including China, India, Russia, Iran and South Africa, have not signed on to the pledge. China’s methane comes in large part from its coal combustion; India’s, from coal as well as waste heaps and biomass fires. And China alone currently releases an estimated 65 million metric tons of methane per year, more than double that of the United States or India, the next two biggest emitters.

With only seven years left before the 2030 deadline, meeting the global pledge’s methane reduction goals would be steep — but, Nisbet says, not impossible.

There’s precedent for successfully making such steep cuts to methane in such a short time, he adds. During the 2000s, “there was a seven-year period where [the U.K. government] brought methane emissions down by 30 percent,” in large part by reducing emissions from landfills and gas leaks.

China has just released its own Methane Emissions Control Action Plan in November, alongside a joint commitment between China and the United States to take action on methane. That news sounds potentially promising, if not wholly reassuring, as the plan does not include a lot of concrete numbers, Nisbet says.

So, what about the oil and gas industry’s recent promise to address its leaky infrastructure? Such a promise also sounds positive on the face of it — leaky infrastructure is definitely the low-hanging fruit when it comes to reducing humans’ methane emissions to the atmosphere (SN: 2/3/22).

On the other hand, hundreds of scientific and environmental organizations have signed an open letter in response. The letter suggests that the oil and gas industry’ promise is just greenwashing, “a smokescreen to hide the reality that we need to phase out oil, gas and coal,” the letter states. Furthermore, many oil and gas companies may routinely abandon old, still-leaking wells — effectively eliminating those leaks from their company’s emissions roster without actually stopping them.

That said, addressing the leaks does have to be done, Nisbet says. “I’d love to shut down the coal industry quickly, but I’m aware of the enormous social problems that brings. It’s a very difficult thing to nuance. You can’t go cold turkey. We’ve got to wind it down in an intelligent and collaborative way. The best thing to do is to stop the crazy leaks and venting.”

Natural methane emission has been surging

Plugging the leaks as soon as possible has taken on an increasing urgency, Nisbet says, because of a stark rise in natural methane being emitted to the atmosphere. Why this rise is happening isn’t clear, but it seems to be some sort of climate change–related feedback, perhaps linked to changes in both temperature and precipitation.

That natural methane emissions bump was also not something that the architects of the Paris Agreement saw coming. Most of that rise has happened since the agreement was signed. From 1999 to 2006, atmospheric methane had spent several years in near-equilibrium — elevated due to human activities, but relatively stable. Then, in 2007, atmospheric methane concentrations began to increase. In 2013, there was a particularly sharp rise, and then again in 2020.

Much of that increase seems to have come from tropical wetlands. Over the past decade, researchers have tracked shifts in methane sources by measuring carbon-12 and carbon-13 in the gas. The ratio of those two forms of carbon in the methane varies significantly depending on the source of the gas. Fossil fuel-derived methane tends to have higher concentrations of carbon-13 relative to carbon-12; methane from wetlands or agriculture tends to be more enriched in carbon-12.

The recent spikes in natural methane are eerily reminiscent of ice core records of “glacial termination” events, times in Earth’s deep past when the world abruptly shifted from a glacial period to a period of rapid warming, Nisbet and others reported in June in Global Biogeochemical Cycles. Such glacial termination events are large-scale reorganizations of the ocean-atmosphere system, involving dramatic changes to the circulation of the global ocean, as well as to large climate patterns like the Indian Ocean Dipole (SN: 1/9/20).

“Is this comparable to the start of a termination event? It looks horribly like that,” Nisbet says. But “it may not be. It might be totally innocent.”

Right now, scientists are racing to understand what’s happening with the natural methane bump, and how exactly the increased emissions might be linked to climate change. But as we search for those answers, there is something that humans can and must do in the meantime, he says: Cut human emissions of the gas as much as possible, as fast as possible. “It’s very simple. When you’re in a hole, stop digging.” More

The world is in a climate crisis — and in the waning days of what’s likely to be the world’s hottest year on record, a new United Nations report is weighing the ethics of using technological interventions to try to rein in rising global temperatures.

“The current speed at which the effects of global warming are increasingly being manifested is giving new life to the discussion on the kinds of climate action best suited to tackle the catastrophic consequences of environmental changes,” the report states.

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A broad variety of climate engineering interventions are already in development, from strategies that could directly remove carbon dioxide from the atmosphere to efforts to modify incoming radiation from the sun (SN: 10/6/19; SN: 7/9/21; SN: 8/8/18).

But “we don’t know the unintended consequences” of many of these technologies, said UNESCO Assistant Director-General Gabriela Ramos at a news conference on November 20 ahead of the report’s release. “There are several areas of great concern. These are very interesting and promising technological developments, but we need an ethical framework to decide how and when to use them.”

Such a framework should be globally agreed upon, Ramos said — and that’s why UNESCO decided to step in. The new report proposes ethical frameworks for both the study and the later deployment of climate engineering strategies.

In addition to explicitly addressing concerns over how tinkering with the climate might affect global food security and the environment, ethical considerations must also include accounting for conflicting interests between regions and countries, the report states. Furthermore, it must include assessing at what point the risks of taking action are or are not morally defensible.   

“It’s not [for] a single country to decide,” Ramos said. “Even those countries that have nothing to do with those technological developments need to be at the table … to agree on a path going forward. Climate is global and needs to be a global conversation.”

The ethics-focused report was prepared by a UNESCO advisory body known as the World Commission on the Ethics of Scientific Knowledge and Technology. Its release coincided with the start of the U.N.’s international climate action summit, the 28th Conference of the Parties, or COP, in Dubai. COP28 runs from November 30 through December 12.

To delve more into the goals of the study and what climate engineering strategies the report considers, Science News talked with report coauthor Inés Camilloni, a climate scientist at the University of Buenos Aires and a resident in the solar geoengineering research program at Harvard University. The conversation has been edited for length and clarity.

SN: There have been a lot of reports recently about climate engineering. What makes this one important?

Camilloni: One thing is that this report includes the views from the Global South as well as the Global North. This is something really important, there are not many reports with the voices of scientists from the Global South. The U.N. Environment Programme’s report this year [on solar radiation modification] was another one. [This new report] has a bigger picture, because it also includes carbon dioxide removal.

I’m a climate scientist; ethics is something new to me. I got involved because I was a lead author of a chapter in the [Intergovernmental Panel on Climate Change] 1.5-degrees-Celsius special report in 2018, and there was a box discussion about climate engineering (SN: 10/7/18). I realized I was not an expert on that. The discussion was among scientists in the Global North, who had a clear position in some ways about the idea, but not Global South scientists. We were just witnessing this discussion.

SN: The report raises a concern about the “moral hazard” of relying too much on climate engineering, which might give countries or companies an excuse to slow carbon emission reductions. Should we even be considering climate engineering in that context?

Camilloni: What we are saying in the report is that the priority must be the mitigation of greenhouse gas emissions. But the discussion on climate engineering is growing because we are not on track to keep temperatures [below] 1.5 degrees C. We are not [at] the right level of ambition really needed to keep temperatures below that target. There are so many uncertainties that it’s relevant to consider the ethical dimensions in these conversations, to make a decision of potential deployment. And in most IPCC scenarios that can limit warming to below 1.5 degrees, carbon dioxide removal is already there.

SN: What are some of the carbon dioxide removal strategies under consideration?

Camilloni: Carbon dioxide removal combines two different methods: Restoring natural carbon sinks, like forests and soils, and investing in technologies that are maybe not yet proven to work at the scale that’s needed. That includes direct air capture [of carbon dioxide] and storage; bioenergy with carbon capture and storage; increasing uptake by the oceans of carbon dioxide, for example by iron fertilization; and enhancing natural weathering processes that remove carbon dioxide from the atmosphere.

But there are potential consequences that need to be considered. Those include negative impacts of terrestrial biodiversity, and effects on marine biodiversity from ocean fertilization. As for sequestering carbon dioxide — how do you store it for hundreds of years or longer, and what are the consequences of rapid release from underground reservoirs? Also there’s potential competition for land [between bioenergy crops or planting trees] and food production, especially in the Global South.

SN: Solar radiation modification is considered even more controversial, but some scientists are saying it should now be on the table (SN: 5/21/10). What type of solar radiation modification is the most viable, technologically?

Camilloni: That’s an umbrella term for a variety of approaches that reduce the amount of incoming sunlight reflected by the atmosphere back to space.

There’s increasing surface reflectivity, for example with reflective paints on structures, or planting more reflective crops (SN: 9/28/18). That reflects more solar radiation into space. It’s already being used in some cities, but it has a very local effect. Similarly, increasing the reflectivity of marine clouds — there were some experiments in Australia to try to protect the Great Barrier Reef, but it seems that also the scale is not global.

Another proposed strategy is to thin infrared-absorbing cirrus clouds — I don’t really know much about that or if it’s really possible. And there’s placing reflectors or shields in space to deflect incoming solar radiation; I also don’t really know if it’s possible to do that.

Injecting aerosols into the stratosphere, to mimic the cooling effect of a volcanic eruption, is the most promising for a global impact. It’s not so challenging in terms of the technology. It’s the only way that we have identified that can cool the planet in a few years.

SN: How soon could aerosol injection be used?

Camilloni: We need at least 10 to 20 years before we can think of deployment. The limitation is that we need the aircraft that can fly at around 20 kilometers altitude. Those are already being designed, but we need about 10 years for those designs, and another 10 to build a fleet of them.

SN: What are some of the ethical concerns around aerosol injection or other solar radiation modification technologies?

Camilloni: These new technologies may be risky in the potential for exacerbating climate problems or introducing new challenges. There are potential risks to changing precipitation patterns, even overcooling in some regions. A key consideration in deciding whether to pursue them is the need for a full characterization of the positive and negative effects of the different technologies around the globe, and a comparison against the risk of not intervening.

SN: In 2021, a research group at Harvard was barred from launching a balloon into the stratosphere to test equipment for possible future aerosol release. How might this report address similar studies?

Camilloni: In our report, we want to make a distinction among the different types of research. You can have indoor research — simulations, social analysis — and this is not so controversial. When you consider outdoor research — releasing particles into the atmosphere — that is more controversial. We are calling for more indoor research. We need to understand the potential impacts.

[For example,] I studied the impact of solar radiation modification on the hydrology of the La Plata Basin [which includes parts of southeastern Brazil, Bolivia, Paraguay, Uruguay and northeastern Argentina]. It’s the most populated region on the continent, and very relevant for hydropower production. And it’s already a very impacted region by climate change.

However, that research was based on just one climate model. We need more — more resources, more capacity building in the Global South. My research group was the first to explore those impacts in Latin and South America. There are others doing research on this over the next few months, but I can count those groups on one hand.

We need more resources to be part of any discussion. Those resources include the Loss and Damage Fund to provide support to nations most vulnerable to the climate crisis [agreed to at the end of COP27 in 2022]. But nobody really knows now how that will be implemented.

SN: The report’s release was timed to the start of COP28. What are you hoping that policymakers will take away from it over the next two weeks?

Camilloni: These recommendations are really important to have in mind, of course. We need more research to make a decision about whether this is a good idea or a bad idea. And maybe people will cut admissions faster if they’re afraid of climate engineering. More

This summer was the hottest ever recorded on Earth, and 2023 is on track to be the hottest year. Heat waves threatened people’s health across North America, Europe and Asia. Canada had its worst wildfire season ever, and flames devastated the city of Lahaina in Maui. Los Angeles was pounded by an unheard-of summer tropical storm while rains in Libya caused devastating floods that left thousands dead and missing. This extreme weather is a warning sign that we are living in a climate crisis, and a call to action.

Carbon dioxide emissions from burning fossil fuels are the main culprit behind climate change, and scientists say they must be reined in. But there’s another greenhouse gas to deal with: methane. Tackling methane may be the best bet for putting the brakes on rising temperatures in the short term, says Rob Jackson, an Earth systems scientist at Stanford University and chair of the Global Carbon Project, which tracks greenhouse gas emissions. “Methane is the strongest lever we have to slow global warming over the next few decades.”

That’s because it’s relatively short-lived in the atmosphere — methane lasts about 12 years, while CO2 can stick around for hundreds of years. And on a molecule-per-molecule basis, methane is more potent. Over the 20-year period after it’s emitted, methane can warm the atmosphere more than 80 times as much as an equivalent amount of CO2.

We already have strategies for cutting methane emissions — fixing natural gas leaks (methane is the main component of natural gas), phasing out coal (mining operations release methane), eating less meat and dairy (cows burp up lots of methane) and electrifying transportation and appliances. Implementing all existing methane-mitigation strategies could slow global warming by 30 percent over the next decade, research has shown.

But some climate scientists, including Jackson, say we need to go further. Several methane sources will be difficult, if not impossible, to eliminate. That includes some human-caused emissions, such as those produced by rice paddies and cattle farming — though practices do exist to reduce these emissions (SN: 11/28/15, p. 22). Some natural sources are poised to release more methane as the world warms. There are signs that tropical wetlands are already releasing more of the gas into the atmosphere, and rapid warming in the Arctic could turn permafrost into a hot spot for methane-making microbes and release a bomb of methane stored in the currently frozen soil.

So scientists want to develop ways to remove methane directly from the air.

Three billion metric tons more methane exist in the atmosphere today than in preindustrial times. Removing that excess methane would cool the planet by 0.5 degrees Celsius, Jackson says.

Similar “negative emissions” strategies are already in limited use for CO2. That gas is captured where it’s emitted, or directly from the air, and then stored somewhere. Methane, however, is a tricky molecule to capture, meaning scientists need different approaches.

Most ideas are still in early research stages. The National Academies of Sciences, Engineering and Medicine is currently studying these potential technologies, their state of readiness and possible risks, and what further research and funding are needed. Some of the approaches include re-engineering bacteria that are already pros at eating methane and developing catalytic reactors to place in coal-mine vents and other methane-rich places to chemically transform the gas.

“Methane is a sprint and CO2 is a marathon,” says Desirée Plata, a civil and environmental engineer at MIT. For scientists focused on removing greenhouse gases, it’s off to the races.

Microbes already remove methane from the air

Methane, CH4, is readily broken down in the atmosphere, where sunshine and highly reactive hydroxyl radicals are abundant. But it’s a different story when chemists try to work with the molecule. Methane’s four carbon-hydrogen bonds are strong and stable. Currently, chemists must expose the gas to extremely high temperatures and pressures to break it down.

Even getting hold of the gas is difficult. Despite its potent warming power, it’s present in low concentrations in the atmosphere. Only 2 out of every 1 million air molecules are methane (by comparison, about 400 of every 1 million air molecules are CO2). So it’s challenging to grab enough methane to store it or efficiently convert it into something else.

Nature’s chemists, however, can take up and transform methane even in these challenging conditions. These microbes, called methanotrophs, use enzymes to eat methane. The natural global uptake of methane by methanotrophs living in soil is about 30 million metric tons per year. Compare that with the roughly 350 million tons of methane that human activities pumped into the atmosphere in 2022, according to the International Energy Agency.

Microbiologists want to know whether it’s possible to get these bacteria to take up more methane more quickly.

Lisa Stein, a microbiologist at the University of Alberta in Edmonton, Canada, studies the genetics and physiology of these microbes. “We do basic research to understand how they thrive in different environments,” she says.

Methanotrophs work especially slowly in low-oxygen environments, Stein says, like wetland muck and landfills, the kinds of places where methane is plentiful. In these environments, microbes that make methane, called methanogens, generate the gas faster than methanotrophs can gobble it up.

But it might be possible to develop soil amendments and other ecosystem modifications to speed microbial methane uptake, Stein says. She’s also talking with materials scientists about engineering a surface to encourage methanotrophs to grow faster and thus speed up their methane consumption.

Scientists hope to get around this speed bump with a more detailed understanding of the enzyme that helps many methanotrophs feast on methane. Methane monooxygenase, or MMO, grabs the molecule and, with the help of copper embedded in the enzyme, uses oxygen to break methane’s carbon-hydrogen bonds. The enzyme ultimately produces methanol that the microbes then metabolize.

Boosting MMO’s speed could not only help with methane removal but also allow engineers to put methanotrophs to work in industrial systems. Turning methane into methanol would be the first step, followed by several faster reactions, to make an end product like plastic or fuel.

Some bacteria, including Methylococcus capsulatus (shown), naturally break down methane with the enzyme methane monooxygenase. By studying the enzyme’s structure, scientists hope to speed up bacteria’s uptake of the greenhouse gas.Anne Fjellbirkeland/Wikimedia Commons (CC BY 2.5)

“Methane monooxygenases are not superfast enzymes,” says Amy Rosenzweig, a chemist at Northwestern University in Evanston, Ill. Any reaction involving MMO will impose a speed limit on the proceedings. “That is the key step, and unless you understand it, it’s going to be very difficult to make an engineered organism do what you want,” Rosenzweig says.

Enzymes are often shaped to fit their reactants — in this case, methane — like a glove. So having a clear view of MMO’s physical structure could help researchers tweak the enzyme’s actions. MMO is embedded in a lipid membrane in the cell. To image it, structural biologists have typically started by using detergents to remove the lipids, which inactivates the enzyme and results in an incomplete picture of it and its activity. But Rosenzweig and colleagues recently managed to image the enzyme in this lipid context. This unprecedented view of MMO in its native state, published in 2022 in Science, revealed a previously unseen site where copper binds.

But that’s still not the entire picture. Rosenzweig says she hopes her structural studies, along with other work, will lead to a breakthrough soon enough to help forestall further consequences of global warming. “Maybe people get lucky and engineer a strain quickly,” Rosenzweig says. “You don’t know until you try.”

Chemists make progress on catalysts

Other scientists seek to put methane-destroying chemical reactors close to methane sources. These reactors typically use a catalyst to speed up the chemical reactions that convert methane into a less planet-warming molecule. These catalysts often require high temperatures or other stringent conditions to operate, contain expensive metals like platinum, and don’t work well at the concentrations of methane found in ambient air.

One promising place to start, though, is coal mines. Coal mining is associated with tens of millions of tons of methane emissions worldwide every year. Although coal-fired power plants are being phased out in many countries, coal will be difficult to eliminate entirely due to its key role in steel production, says Plata, of MIT.

To develop a catalyst that might work in a coal mine, Plata found inspiration in MMO. Her team developed a catalyst material based on a silicate material embedded with copper — the same metal found in MMO and much less expensive than those usually required to oxidize methane. The material is also porous, which improves the catalyst’s efficiency because it has a larger surface area, and thus more places for reactions to occur, than a nonporous material would. The catalyst turns methane into CO2, a reaction that releases heat, which is needed to further fuel the reaction. If methane concentrations are high enough, the reaction will be self-sustaining, Plata says.

Turning methane into CO2 may sound counterproductive, but it reduces warming overall because methane traps much more heat than CO2 and is far less abundant in the atmosphere. If all the excess methane in the atmosphere were turned into CO2, according to a 2019 study led by Jackson, it would result in only 8.2 billion additional tons of CO2 — equivalent to just a few months of CO2 emissions at today’s rates. And the net effect would be to lessen the heating of the atmosphere by a sixth.

Cattle feedlots are another place where Plata’s catalytic reactor might work. Barns outfitted with fans to keep cattle comfortable move air around, so reactors could be fitted to these ventilation systems. The next step is determining whether methane concentrations at industrial dairy farms are high enough for the catalyst to work.

At Drumgoon Dairy in South Dakota, Elijah Martin (left) and Will Sawyer (right) test a small-scale thermal catalytic unit developed in Desirée Plata’s lab at MIT. The reactor transforms methane into carbon dioxide, which could lower the planet’s net warming rate because methane is a stronger greenhouse gas.D. Plata

Another researcher making progress is energy scientist and engineer Arun Majumdar, one of Jackson’s collaborators at Stanford. In January, Majumdar published initial results describing a catalyst that converts methane into methanol, with an added boost from high-energy ultraviolet light. This UV blast adds the energy needed to overcome CH4’s stubborn bonds — and the carefully designed catalyst stays on target. Previous catalyst designs tended to produce a mix of CO2 and methanol, but this catalyst mostly sticks to making methanol.

Is geoengineering a path to methane removal?

A more extreme approach to speed up methane’s natural breakdown is to change the chemistry of the atmosphere itself. A few companies, such as the U.S.-based Blue Dot Change, have proposed releasing chemicals into the sky to enhance methane oxidation.

Natalie Mahowald, an atmospheric chemist at Cornell University, decided to evaluate this type of geoengineering.

“I’m not super excited about throwing more things into the atmosphere,” Mahowald says. To meet the goals of the Paris Agreement, limiting global warming to 1.5 to 2 degrees Celsius above the preindustrial average, though, it’s worth exploring all possibilities, she says. “If we’re going to meet these targets,” she says “we’re going to need some of these crazy ideas to work. So I’m willing to look at it. But I’m looking with a scientist’s critical eye.”

The main strategy proposed by advocates would inject iron aerosols into the air over the ocean on a sunny day. These aerosols would react with salty sea spray aerosols to form chlorine, which would then attack methane in the atmosphere and initiate further chemical reactions that turn it into CO2. Mahowald wondered how much chlorine would be needed — and if there might be any unintended consequences.

Detailed modeling revealed something alarming. The iron injections could have the opposite of the intended effect, Mahowald and colleagues reported in July in Nature Communications. Chlorine won’t attack methane if ozone is around. Instead, chlorine will first break down all the ozone it can find. But ozone plays a key role in generating the hydroxyl radicals that naturally break down atmospheric methane. So when ozone levels fall, Mahowald says, the concentration and lifetime of methane molecules in the atmosphere actually increases. To use this strategy to break down methane, geo­engineers would need to add a tremendous amount of chlorine to the atmosphere — enough to first break down the ozone, then attack methane.

Removing 20 percent of the atmosphere’s methane, thus reducing the planet’s surface temperature by 0.2 degrees Celsius by 2050, for example, would require creating about 630 million tons of atmospheric chlorine every year. That would in turn require injecting perhaps tens of millions of tons of iron. A form of particulate matter, these iron aerosols could worsen air quality; inhaling particulate matter is associated with a range of health problems, particularly cardiovascular and lung disease. This atmospheric tinkering could also create hydrochloric acid that could reach the ocean and acidify it.

And there’s no guarantee that some of the chlorine wouldn’t make it all the way up to the ozone layer, depleting the planetary shield that protects us from the sun’s harmful UV rays. Mahowald is still studying this possibility.

Methane is a sprint and CO2 is a marathon. Desirée Plata

Mahowald is ambivalent about doing research on geoengineering. “We’re just throwing out ideas here because we’re in a terrible, terrible position,” she says. She’s worried about what could happen if all the methane locked up in the world’s permafrost escapes. If scientists can figure out how to use iron aerosols effectively, without adverse effects — and if such geoengineering is accepted by society — we might need it.

“We’re just trying to see, is there any hope this could work and would we ever want to do it? Would it have enough benefits to outweigh the disadvantages?”

The committee organized by the National Academies to investigate methane removal is taking these kinds of ethical questions into account, as well as considering the potential cost and scale of technologies. Stein, a committee member, says a framework proposed by Spark Climate Solutions provides some guidance. The organization, a nonprofit based in San Francisco that evaluates methane-removal technologies, proposes investing in tech that can remove tens of millions of tons of methane per year in the coming decades, at a cost of less than $2,000 per ton. Spark cofounder David Mann says the numbers are designed to focus attention and investment on technologies that can make a real difference in curbing climate change in the near term.

The National Academies group aims to make recommendations about research priorities on methane-removal technologies by next summer. It’s likely that a portfolio of different technologies will be necessary. What works in a cattle feedlot may not work at a wastewater treatment plant, for instance.

Scientists focused on methane removal are eager for more researchers, research funding and companies to enter the fray — and quickly. “It’s been a crazy year,” Jackson says of 2023’s extreme weather. We’re already feeling the effects of global warming, but we can seize the moment, he says. “This problem is not something for our grandchildren. It’s here.” More

The last 12 months were the hottest in 150 years of recordkeeping — and probably in the last 125,000 years — thanks to human-caused climate change, a new report finds.

From November 2022 through October 2023, the planet’s average temperature was about 1.3 degrees Celsius higher than the average temperature from 1850 to 1900, say researchers with the nonprofit group Climate Central. That’s just shy of the 1.5-degree threshold often cited as a benchmark for avoiding irreversible impacts on the climate (SN: 1/11/22).

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And over the past year, about 1 in 4 people around the world experienced a climate change–driven heat wave that lasted at least five days, the scientists found.

The report, released on November 9, comes just ahead of the 28th United Nations Climate Change Conference of the Parties, which begins on November 30. That’s intentional, says Andrew Pershing, vice president for science at Climate Central. There is no doubt that fossil fuels are driving most of this heat, and it’s to be hoped that the world’s nations will take note of these findings, he says (SN: 4/4/22).

Global average numbers can be hard to grasp. So the new report also quantifies temperatures that people around the world are actually experiencing day-to-day, and how much those are attributable to climate change, Pershing says.

“We have these super important global numbers such as the 1.5- or 2-degree warming targets, but that isn’t the experience that people on planet Earth have,” he says (SN: 12/17/18). “We wanted to develop a way to really localize that experience … to talk about how climate change influenced that day’s temperatures on any given day anywhere in the planet.”

To that end, the analysis used Climate Central’s Climate Shift Index, or CSI, a system first described by the organization in 2022. CSI is a daily local temperature attribution system that uses a combination of observational data and climate simulations to determine the likelihood that local temperature variations are attributable to climate change.

Extreme heat is a relative term, dependent on both place and time. So, in this report, the researchers considered extreme heat for a given location to be daily temperatures that would have been in the 99th percentile for that place from 1991 to 2020 — temperatures, in other words, that locals would recognize as insanely hot.

Using that index with data from hundreds of countries, states, provinces and major cities, the researchers found that about 90 percent of the world’s population, or 7.3 billion people, experienced at least 10 days of extreme temperatures in the last year that were very strongly affected by climate change.

Those days had a CSI rating of at least 3, indicating that human-caused climate change made those temperatures at least three times as likely. Nearly 3 out of 4 people experienced over a month of those temperatures.

The report also reveals stark inequities in the burden of climate change around the world. Earth’s least developed countries, including many nations in sub-Saharan Africa and in Southeast Asia, had a relatively high average CSI of 2, the report notes, though they have contributed the least amount of fossil fuel emissions.

But climate impacts are also accelerating in many of the world’s richest countries, including the United States. The last 12 months saw brutal heat waves across much of the southern United States. Houston sweltered through a 22-day streak of extreme heat, where each consecutive day topped 38° C (100° Fahrenheit). That was the longest such extreme heat streak of the 700 cities examined with a population of at least 1 million people.

The CSI analysis is similar to the analyses performed by the consortium World Weather Attribution, or WWA, which looks for the fingerprints of human-caused climate change in specific extreme events around the world (SN: 7/25/23).

WWA examined a handful of extreme heat waves over the last 12 months, all of which were strongly attributable to climate change, says Friederike Otto, a climate scientist at Imperial College London who has led many of WWA’s attribution studies.

An immediate reduction of fossil fuels won’t shut off some effects of a century of emissions, including heat absorbed by the oceans or melted glaciers, Otto says. But global temperatures would stop rising, and heat waves would stop getting worse, she says. Keeping the planet below a 1.5-degree warming threshold “is in reach,” she says, “if we want it to be in reach.”

The last 12 months saw the onset of an El Niño climate pattern, which can bring higher global temperatures on top of the longer-term global warming trend (SN: 6/15/23). But the greatest temperature impact from El Niño generally takes a year or so to develop, as the heat gets disseminated around the globe, Pershing says.

The previous 12-month record was set from October 2015 to September 2016, as heat from a strong El Niño event spread around the globe. That record — where the global average was 1.29 degrees Celsius higher than the average preindustrial temperature — was tied earlier this year, for the period ending in September 2023.

That means that, as the El Niño pattern continues to develop into next year, 2024 will probably smash records once again. More

Luis Melecio-Zambrano was the summer 2023 science writing intern at Science News. They are finishing their master’s degree in science communication from the University of California, Santa Cruz, where they have reported on issues of environmental justice and agriculture. More

On the morning of September 5, a loosely swirling system of thunderstorms formed off the western coast of Africa. By September 6, the system had become a Category 1 storm, with maximum winds at least 130 kilometers per hour (80 miles per hour).

Just 24 hours later, fueled by the record-warm waters of the North Atlantic Ocean, Hurricane Lee whipped itself into a Category 5 monster. In that short time span, its wind speeds doubled, to 260 kilometers per hour (160 miles per hour).

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As the world’s oceans continue to stockpile heat from global warming, stories of such rapid intensification of tropical cyclones are becoming more commonplace, and not just in the Atlantic.

“While all eyes are on [Hurricane Lee], [Hurricane Jova] is bombing out in the eastern Pacific,” wrote Miami-based U.S. National Hurricane Center meteorologist Eric Blake on X, formerly called Twitter, on September 6. “This was just named 36 hours ago and has exploded into a Category 4 hurricane.”

These storms formed just weeks after Hurricane Idalia, which also rapidly intensified. Its wind speeds cranked up from about 120 kph to 209 kph (or 75 mph to 130 mph) in 24 hours. Shortly afterward, Idalia slammed into Florida’s Gulf Coast.

All of these hurricanes easily met — and some greatly exceeded — the National Hurricane Center’s definition of rapid intensification, in which a storm’s maximum sustained winds jump by at least 56 kph (35 mph) in less than a day. Such storms can leave people little time to prepare, making the hurricanes particularly dangerous to lives and property.

Here ‘s what to know about such rapidly intensifying storms.

A warmer ocean and atmosphere can supercharge storms

The key ingredients to boost a storm’s power quickly are very warm ocean waters, a lot of moisture in the atmosphere and low vertical wind shear, says atmospheric scientist Philip Klotzbach of Colorado State University in Fort Collins (SN: 9/28/18; SN: 9/13/18).

Vertical wind shear is what happens when winds at different heights in the atmosphere are moving at different speeds and in different directions. Those winds can chip away at a storm as it tries to organize into a tight swirl by pulling heat and moisture away from the storm’s center and sweeping away the upper structure of the storm.

This year saw the onset of an El Niño phase of the El Niño-Southern Oscillation ocean-climate pattern, a phase that tends to bring more vertical wind shear conditions to the North Atlantic. That means that El Niño years tend to feature fewer Atlantic tropical storms (SN: 5/26/23).

But so far in 2023, El Niño hasn’t done much to minimize hurricane formation, or dampen the storms’ power. “The first half of the season has not seen the unfavorable upper-level wind conditions in the western Atlantic that are typically observed in an El Niño year,” says Ryan Truchelut, president and chief meteorologist of WeatherTiger, a weather consulting firm based in Tallahassee, Fla. That’s true even in the Caribbean Sea, where El Niño’s shearing power tends to be strongest, Truchelut adds.

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Generally, there’s more of a contrast in temperature between the Atlantic and Pacific ocean basins during an El Niño year — the weather pattern heats up the eastern tropical Pacific while the Atlantic stays relatively cool.  But 2023 has seen record-breaking ocean temperatures in the North Atlantic Ocean and in the Gulf of Mexico (SN: 6/15/23). While the El Niño-warmed Pacific is about 1.5 degrees Celsius above normal, parts of the Atlantic are 1 to 3 degrees C above normal.

“Temperature contrasts drive jets,” Trechelut says, “and the lack of this contrast is likely responsible for the missing shear.”

The extremely warm waters of the Atlantic and the Gulf of Mexico set the stage — all the storms needed was a window of time with favorable wind conditions, says John Kaplan, a hurricane modeler with the U.S. National Oceanographic and Atmospheric Administration’s Atlantic Oceanographic and Meteorological Laboratory, based in Miami.  “What it really comes down to is whether the conditions for rapid intensification are favorable for even a short period of time,” he says. “If there’s a window — even if not a very long one — the system can take advantage of it. That was the case for both Lee and Idalia.”

More storms are rapidly intensifying as Earth warms

It certainly feels like most of the hurricanes in recent years are rapidly intensifying (SN: 8/27/20). But is that a true trend? And if it is, is it linked to climate change?

Studies suggest that it’s not just anecdotal. In August, researchers reported that the yearly number of tropical storms around the globe that rapidly intensified just offshore (within 400 kilometers of land) increased by about three a decade over the last 40 years, from fewer than five per year in the 1980s to about 15 per year by 2020.

Open-ocean storms, spinning far out in the big blue, showed no discernible trend, the team found. But that’s perhaps not wholly reassuring, as it’s the storms closer to shore that are most threatening to coastal populations. And a 2021 study reported that tropical cyclones have been migrating closer to the coasts since 1982.

In 2019, another team focused on observational records of wind-speed changes over 24-hour increments. Based on those data, the researchers found that episodes of rapid intensification in tropical storms tripled from 1982 to 2009. Using climate simulations, the team researchers determined that the rapid intensification trend was strongly linked to anthropogenic human-caused climate change.

Truchelut notes that the same team authored a 2022 study that further supported an upward trend over the last few decades, determining that a larger proportion of tropical cyclones are now undergoing rapid intensification at some point in their life cycle.

Regional and local weather patterns — such as more frequent La Niña events (the flipside of the El Niño-Southern Oscillation pattern) — “could dampen rapid intensification trends locally,” Truchelut says. “But there is strong objective evidence that anthropogenic global warming is driving increased proportions of tropical cyclones to undergo rapid intensification worldwide.”

Klotzbach and colleagues, meanwhile, found another fingerprint of climate change in the rapid intensification of cyclones. The researchers reported in 2022 that the increase in global sea surface temperatures correlate well with an increase in the potential intensity of tropical cyclones around the world — essentially, just how strong the winds are capable of becoming — over the last 30 years. That observed increase was particularly apparent for the most monstrous storms — those whose wind speeds increased by a whopping 93 kph (57 mph) in a single day.

Despite the fury of Lee and Jova, their threat has largely fizzled. Hurricane Lee downgraded to a Category 3 by September 12 and curved northward; however, it’s also tripled in size, threatening Bermuda with tropical storm force winds. Hurricane Jova, meanwhile, ultimately spun harmlessly in the Pacific before weakening.

But with the hurricane season only half over, there’s still time for all that hot water to fuel the next big ones. More