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carbon dioxide removal
Study Warns of 'Irreversible Impacts' From Overshooting 1.5°C, Even Temporarily
"Only by doing much more in this critical decade to bring emissions down and peak temperatures as low as possible, can we effectively limit damages."
Oct 09, 2024
Just over a month away from the next United Nations climate summit, a study out Wednesday warns that heating the planet beyond a key temperature threshold of the Paris agreement—even temporarily—could cause "irreversible impacts."
The 2015 agreement aims to limit global temperature rise this century to 1.5ºC, relative to preindustrial levels.
"For years, scientists and world leaders have pinned their hopes for the future on a hazy promise—that, even if temperatures soar far above global targets, the planet can eventually be cooled back down," The Washington Postdetailed Wednesday. "This phenomenon, known as a temperature 'overshoot,' has been baked into most climate models and plans for the future."
"The earlier we can get to net-zero, the lower peak warming will be, and the smaller the risks of irreversible impacts."
As lead author Carl-Friedrich Schleussner said in a statement, "This paper does away with any notion that overshoot would deliver a similar climate outcome to a future in which we had done more, earlier, to ensure to limit peak warming to 1.5°C."
"Only by doing much more in this critical decade to bring emissions down and peak temperatures as low as possible, can we effectively limit damages," stressed Schleussner, an expert from Climate Analytics and the International Institute of Applied Systems Analysis who partnered with 29 other scientists for the study.
The paper, published in the peer-reviewed journal Nature, states that "for a range of climate impacts, there is no expectation of immediate reversibility after an overshoot. This includes changes in the deep ocean, marine biogeochemistry and species abundance, land-based biomes, carbon stocks, and crop yields, but also biodiversity on land. An overshoot will also increase the probability of triggering potential Earth system tipping elements."
"Sea levels will continue to rise for centuries to millennia even if long-term temperatures decline," the study adds, projecting that every 100 years of overshoot could lead seas to rise nearly 16 inches by 2300, on top of more than 31 inches without overshoot.
The scientists found that "a similar pattern emerges" for the thawing of permafrost—ground that is frozen for two or more years—and northern peatland warming, which would lead to the release of planet-heating carbon dioxide and methane. They wrote that "the effect of permafrost and peatland emissions on 2300 temperatures increases by 0.02ºC per 100 years of overshoot."
"To hedge and protect against high-risk outcomes, we identify the geophysical need for a preventive carbon dioxide removal capacity of several hundred gigatonnes," the authors noted. "Yet, technical, economic, and sustainability considerations may limit the realization of carbon dioxide removal deployment at such scales. Therefore, we cannot be confident that temperature decline after overshoot is achievable within the timescales expected today. Only rapid near-term emission reductions are effective in reducing climate risks."
In other words, as co-author and Climate Analytics research analyst Gaurav Ganti, put it, "there's no way to rule out the need for large amounts of net negative emissions capabilities, so we really need to minimize our residual emissions."
"We cannot squander carbon dioxide removal on offsetting emissions we have the ability to avoid," Ganti added. "Our work reinforces the urgency of governments acting to reduce our emissions now, and not later down the line. The race to net-zero needs to be seen for what it is—a sprint."
While the paper comes ahead of COP29, the U.N. conference in Azerbaijan next month, co-author Joeri Rogelj looked toward COP30, for which governments that have signed the Paris agreement will present their updated nationally determined contributions (NDCs) to meet the climate deal's goals.
"Until we get to net-zero, warming will continue. The earlier we can get to net-zero, the lower peak warming will be, and the smaller the risks of irreversible impacts," said Rogelj, a professor and director of research for the Grantham Institute at Imperial College London. "This underscores the importance of countries submitting ambitious new reduction pledges, or so-called 'NDCs,' well ahead of next year's climate summit in Brazil."
The U.N. said last November that countries' current emissions plans would put the world on track for 2.9°C of warming by 2100, nearly double the Paris target. Since then, scientists have confirmed that 2023 was the hottest year in human history and warned that 2024 is expected to set a new record.
The study in Nature was published as Hurricane Milton—fueled by hot waters in the Gulf of Mexico—barreled toward Florida and just a day after another group of scientists wrote in BioScience that "we are on the brink of an irreversible climate disaster. This is a global emergency beyond any doubt. Much of the very fabric of life on Earth is imperiled."
Those experts emphasized that "human-caused carbon dioxide emissions and other greenhouse gases are the primary drivers of climate change. As of 2022, global fossil fuel combustion and industrial processes account for approximately 90% of these emissions, whereas land-use change, primarily deforestation, accounts for approximately 10%."
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Climate Groups Reject 'Risky, Untested' Technofixes in IPCC Report
"Solving the climate crisis is not about what works on paper but what delivers in practice. There is no time to waste with false solutions."
Mar 20, 2023
Longtime critics of "false solutions" to the fossil fuel-driven climate emergency responded to a United Nations report released Monday by reiterating their warnings about relying on underdeveloped and untested technologies that could enable major polluters to continue producing massive amounts of planet-heating emissions.
Noting the 2015 Paris agreement's two primary temperature targets for this century, the new Intergovernmental Panel on Climate Change (IPCC) report states that "all global modeled pathways that limit warming to 1.5°C with no or limited overshoot, and those that limit warming to 2°C, involve rapid and deep and, in most cases, immediate" greenhouse gas (GHG) emissions reductions in all sectors this decade.
"We must heed the IPCC's urgent messages, without falling into the trap of assuming that carbon dioxide removal will save the day."
Modeled mitigation pathways, the report continues, "include transitioning from fossil fuels without carbon capture and storage (CCS) to very low- or zero-carbon energy sources, such as renewables or fossil fuels with CCS, demand-side measures and improving efficiency, reducing non-CO2 GHG emissions," and carbon dioxide removal (CDR).
As the document details:
CCS is an option to reduce emissions from large-scale fossil-based energy and industry sources provided geological storage is available. When CO2 is captured directly from the atmosphere (DACCS), or from biomass (BECCS), CCS provides the storage component of these CDR methods. CO2 capture and subsurface injection is a mature technology for gas processing and enhanced oil recovery. In contrast to the oil and gas sector, CCS is less mature in the power sector, as well as in cement and chemicals production, where it is a critical mitigation option. The technical geological storage capacity is estimated to be on the order of 1000 GtCO2, is more than the CO2 storage requirements through 2100 to limit global warming to 1.5°C, although the regional availability of geological storage could be a limiting factor. If the geological storage site is appropriately selected and managed, it is estimated that the CO2 can be permanently isolated from the atmosphere.
"Implementation of CCS currently faces technological, economic, institutional, ecological environmental and socio-cultural barriers," the report notes. "Currently, global rates of CCS deployment are far below those in modeled pathways limiting global warming to 1.5°C to 2°C. Enabling conditions such as policy instruments, greater public support, and technological innovation could reduce these barriers."
The report further says that "biological CDR methods like reforestation, improved forest management, soil carbon sequestration, peatland restoration, and coastal blue carbon management can enhance biodiversity and ecosystem functions, employment and local livelihoods. However, afforestation or production of biomass crops can have adverse socioeconomic and environmental impacts, including on biodiversity, food and water security, local livelihoods, and the rights of Indigenous peoples, especially if implemented at large scales and where land tenure is insecure."
While the world's top scientists—and the governments that signed off on the report—recognized issues with CCS and CDR, climate campaigners expressed frustration that such technologies were featured as partial solutions.
"It's very alarming to see carbon dioxide removal featuring so centrally in the IPCC report," declared Sara Shaw at Friends of the Earth International (FOEI). "We can't rely on risky, untested, and downright dangerous removals technologies just because big polluters want us to stick to the status quo."
"A fair and fast phaseout of oil, gas, and coal needs to happen in this decade, and it can, with the right political will," she stressed. "We must heed the IPCC's urgent messages, without falling into the trap of assuming that carbon dioxide removal will save the day."
Fellow FOIE leader Hemantha Withanage explained that "in my country, Sri Lanka, the impacts of climate change are being felt now. We have no time to chase fairy tales like carbon removal technologies to suck carbon out of the air."
"The IPCC evidence is clear: Climate change is killing people, nature, and planet," he said. "The answers are obvious: a fair and fast phaseout of fossil fuels, and finance for a just transition. The fantasy of overshooting safe limits and betting on risky technofixes is certainly not a cure for the problem."
Lili Fuhr at the Center for International Environmental Law agreed that "the takeaway of the IPCC synthesis is irrefutable: An immediate, rapid, and equitable fossil fuel phaseout is the cornerstone of any strategy to avoid catastrophic levels of global warming."
"Building our mitigation strategies on models that instead lock in inequitable growth and conveniently assume away the risks of technofixes like carbon capture and storage and carbon dioxide removal ignores that clarion message and increases the likelihood of overshoot," Fuhr warned. "The most ambitious mitigation pathways put out by the IPCC set the floor, not the ceiling, for necessary climate action.
Research shows that overshooting Paris temperature targets, even temporarily, could dramatically raise the risk of the world experiencing dangerous "tipping points," as Common Dreams reported in December. The IPCC report notes that "the higher the magnitude and the longer the duration of overshoot, the more ecosystems and societies are exposed to greater and more widespread changes in climatic impact-drivers, increasing risks for many natural and human systems."
As Corporate Accountability director of climate research and policy Rachel Rose Jackon put it Monday: "Breaching 1.5°C is not an option. Governments will be effectively signing millions of avoidable death warrants for those who contributed least to the crisis."
While arguing that the IPCC document "demands a last and final reckoning" that leads to Global North governments "doing their fair share," the campaigner also emphasized that "the report should have actually named the solutions that will keep us below 1.5°C instead of leaving the door open for an inadequate suite of industry-backed removals and dangerous distractions."
Food & Water Watch executive director Wenonah Hauter targeted U.S. lawmakers and President Joe Biden in a statement Monday.
"The IPCC is sending one key message above all else: We must stop burning fossil fuels, drilling for fossil fuels, and building new infrastructure to deliver fossil fuels," Hauter said. "Unfortunately, policymakers continue to lock in new dirty energy schemes—most notably the Biden administration's approval of a massive new oil drilling project in Alaska."
"Tragically, Congress and the White House continue to waste money on carbon removal technologies that have been a failure. Relying on these scams instead of taking actions to stop fossil fuel expansion will only lead to further climate catastrophe," she added. "President Biden's actions to expand oil and gas drilling and ramp up fossil fuel exports undermine his professed climate goals and invite further catastrophe. The IPCC's message is clear, and political leaders must answer the call with actions to match the moment."
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