Despite progress since the Paris Agreement, a peak in greenhouse gas emissions is only just within sight – and time is fast running out to stay below 1.5C of human-caused global warming since the preindustrial era.
As a result, almost all pathways that keep 1.5C within reach now involve a temporary “overshoot”.
This term refers to a period where the best estimate of warming exceeds 1.5C, until temperatures are brought back below the limit by removing carbon dioxide (CO2) from the atmosphere.
While this idea is growing in prominence, there have only been limited efforts to understand what it would mean to breach the 1.5C limit, even if this is only during a temporary period of overshoot.
In a new Nature paper, we present the findings of a three-year Horizon Europe-funded project, looking at what overshoot means for emissions, temperatures, climate impacts and adaptation.
Our results show that overshooting 1.5C comes with significant uncertainty in terms of warming outcomes, climate impacts and associated risks. For example, climate uncertainty means that what is referred to as a 1.5C “pathway” carries a notable risk of much greater levels of warming.
In order to hedge against the risk of higher-than-expected warming, the world would need to develop substantial capacity for “net-negative” CO2 emissions. This could be used to reverse a temporary overshoot and reduce long-term risks, if warming is no more extreme than expected.
Even so, overshoot would come with irreversible consequences for humans and ecosystems, our research finds, such as rising sea levels and ecosystem loss.
Overshoot overconfidence
The Intergovernmental Panel on Climate Change (IPCC) has been key to shaping our understanding of overshoot scenarios. In its latest sixth assessment report (AR6), the IPCC considered a range of pathways that limit median warming in 2100 to below 1.5C.
The report categorised the pathways according to their probability of breaching 1.5C, but also offered information on the amount of any expected overshoot.
Specifically, the C1 “no or limited overshoot” pathways allow an overshoot of “up to about 0.1C”. The C2 pathways return warming to 1.5C “after a high overshoot” of between “0.1C-0.3C”.
These categorisations give the impression that overshoot can be neatly and confidently constrained – to within a few tenths of a degree – and that in choosing a particular pathway, the countries of the world would have full control over the planetary thermostat.
Crucially, however, the numbers refer only to median warming outcomes. Considering the uncertainties in Earth system feedbacks, it is not possible to rule out much higher peak warming. For example, this could be up to 2.5C under C2 scenarios (at the 95th percentile of all model runs).
If the increase in temperatures is indeed much higher than expected under median warming, or if warming continues even when CO2 emissions reach net-zero, then returning to below 1.5C after an overshoot would require much more CO2 removal than thought.
Even with stringent emissions reductions, we therefore cannot rule out the possibility that reversing a 1.5C overshoot would require the removal of hundreds of billions of tonnes CO2 by 2100.
Indeed, based on the simple climate model FaIR, our findings show that 400GtCO2 of additional removals could be needed to return temperatures to 1.5C by 2100, if warming reaches the 75th percentile of expected levels rather than the median (about 1.7C instead of 1.5C, an outcome with a likelihood of one-in-four).
(This is based on generating more than 2,000 physically plausible climate outcomes for an emission pathway that limits median warming to around 1.5C and achieves net-zero CO2 by around mid-century, without the need for net-negative emissions thereafter.)
To reach 400GtCO2 of removals by 2100 would mean taking nearly 10GtCO2 out of the atmosphere every year after global CO2 emissions reach net-zero. For comparison, current removals amount to around 2GtCO2 per year, from all sources.
The 400GtCO2 of removals that could be needed to deal with higher-than-expected warming is similar to the amount of removals that is typically being relied on in 1.5C pathways, assuming median levels of warming in response to a given level of emissions.
This is shown in the figure below, where the first row illustrates the range of cumulative CO2 removal needed to return temperatures to below 1.5C by 2100, depending on how sensitive the climate is to a given level of emissions. The bottom two rows show removals in C1 “no or limited overshoot” and C2 “high overshoot” 1.5C pathways, assuming a median warming response.
Our findings imply the world may therefore need a “preventive” capacity to remove hundreds of billions of tonnes of CO2 by 2100, to hedge against the risk of higher-than-expected warming.
Moreover, given the political, economic, sustainability and other constraints on the speed and scale at which CO2 removal can be scaled up, it therefore may not be possible to rely on removals to compensate for a failure to reduce emissions in other parts of the economy.
Irreversible impacts
If warming is no more severe than expected under median outcomes, then preventive CO2 removal capacity could be used to steadily reduce temperatures after overshoot.
This could be an important way to minimise long-term climate risks following overshoot.
For example, for every 100 years of overshoot above 1.5C, our findings show that there would be an additional 40cm of sea-level rise by 2300. There would be similarly irreversible consequences for the world’s frozen ecosystems, such as permafrost and peatlands.
In addition, overshoot increases the risk of crossing irreversible climate “tipping points”.
These findings show that even if a global temperature overshoot is reversed, the temporary breach of the 1.5C limit would still come with some irreversible consequences.
Peak and decline
Our study offers a framework for minimising the risks associated with higher-than-expected warming and potentially irreversible climate impacts after temperature overshoot.
Instead of the current categories of mitigation pathway, which focus on peak warming and end-of-century temperatures – apparently with a high level of precision – our paper suggests “peak and decline” (PD) scenarios that allow us to consider a wide range of plausible climate outcomes.
These scenarios aim to achieve a peak in warming, followed by sustained temperature reductions during a period of at least several decades. Global greenhouse gas (GHG) emissions would need to decline towards net-zero CO2 to achieve temperature peaking, followed by net-negative CO2 emissions to enter a long-term decline.
The “peak” is determined by how fast emissions are reduced in the near term, towards reaching net-zero CO2 emissions. This determines the maximum cumulative CO2 emissions of a pathway and therefore the level and timing of peak warming. Importantly, the stringency of non-CO2 GHG emission reductions will also strongly affect peak warming.
The pace of global temperature “decline” after the peak – and therefore the ability to reverse a temporary exceedance of a target limit – depends on the level of net-negative CO2 emissions that can be achieved.
In PD “overshoot” pathways (PD-OS), warming exceeds 1.5C before returning to that level and staying there into the future. These are similar to PD pathways, but the carbon budget, timing of net-zero CO2 and amount of CO2 removal depends on the length, level and timing of overshoot.
In PD “enhanced protection” pathways (PD-EP), warming is kept as low as possible and gradually reversed over time, to minimise climate risks. They entail stringent, rapid cuts in GHG emissions, achieving net-zero CO2 as soon as possible and using sustainable levels of CO2 removal to reduce warming over time, potentially reaching net-zero or even net-negative GHGs.
These pathways are illustrated in the figure below, where the 1.5C limit is shown as a horizontal dotted line, and the different peak and decline pathways are contrasted with a scenario in which temperatures continue to increase, despite reaching net-zero CO2.
Our findings suggest that a peak and decline “enhanced protection” pathway would offer the best way to hedge against the uncertainties and minimise the risks around overshoot and the response of the climate system. This would entail two actions from countries worldwide.
First, it would mean reducing emissions as fast as possible to slow down temperature increase, reduce peak warming, and reduce the dependency of needing large amounts of CO2 removals to even achieve net-zero CO2 emissions.
Second, it would mean rapidly scaling up global capacity for CO2 removal to hedge against high-risk outcomes from stronger than expected climate feedback.
The scale of preventive removal capacity that we estimate could be needed, is only just achievable within sustainable limits. If some removal capacity is used to compensate for a failure to rapidly reduce emissions, then it would not be available to manage higher-than-expected warming.
Overall, our paper reinforces the idea that earlier emissions reductions are the best way to minimise far-reaching climate risks in the 21st century and beyond.
The post Guest post: How to minimise the risks from overshooting the 1.5C limit appeared first on Carbon Brief.
Guest post: How to minimise the risks from overshooting the 1.5C limit
Climate Change
Cheniere Energy Received $370 Million IRS Windfall for Using LNG as ‘Alternative’ Fuel
The country’s largest exporter of liquefied natural gas benefited from what critics say is a questionable IRS interpretation of tax credits.
Cheniere Energy, the largest producer and exporter of U.S. liquefied natural gas, received $370 million from the IRS in the first quarter of 2026, a payout that shipping experts, tax specialists and a U.S. senator say the company never should have received.
Cheniere Energy Received $370 Million IRS Windfall for Using LNG as ‘Alternative’ Fuel
Climate Change
DeBriefed 27 February 2026: Trump’s fossil-fuel talk | Modi-Lula rare-earth pact | Is there a UK ‘greenlash’?
Welcome to Carbon Brief’s DeBriefed.
An essential guide to the week’s key developments relating to climate change.
This week
Absolute State of the Union
‘DRILL, BABY’: US president Donald Trump “doubled down on his ‘drill, baby, drill’ agenda” in his State of the Union (SOTU) address, said the Los Angeles Times. He “tout[ed] his support of the fossil-fuel industry and renew[ed] his focus on electricity affordability”, reported the Financial Times. Trump also attacked the “green new scam”, noted Carbon Brief’s SOTU tracker.
COAL REPRIEVE: Earlier in the week, the Trump administration had watered down limits on mercury pollution from coal-fired power plants, reported the Financial Times. It remains “unclear” if this will be enough to prevent the decline of coal power, said Bloomberg, in the face of lower-cost gas and renewables. Reuters noted that US coal plants are “ageing”.
OIL STAY: The US Supreme Court agreed to hear arguments brought by the oil industry in a “major lawsuit”, reported the New York Times. The newspaper said the firms are attempting to head off dozens of other lawsuits at state level, relating to their role in global warming.
SHIP-SHILLING: The Trump administration is working to “kill” a global carbon levy on shipping “permanently”, reported Politico, after succeeding in delaying the measure late last year. The Guardian said US “bullying” could be “paying off”, after Panama signalled it was reversing its support for the levy in a proposal submitted to the UN shipping body.
Around the world
- RARE EARTHS: The governments of Brazil and India signed a deal on rare earths, said the Times of India, as well as agreeing to collaborate on renewable energy.
- HEAT ROLLBACK: German homes will be allowed to continue installing gas and oil heating, under watered-down government plans covered by Clean Energy Wire.
- BRAZIL FLOODS: At least 53 people died in floods in the state of Minas Gerais, after some areas saw 170mm of rain in a few hours, reported CNN Brasil.
- ITALY’S ATTACK: Italy is calling for the EU to “suspend” its emissions trading system (ETS) ahead of a review later this year, said Politico.
- COOKSTOVE CREDITS: The first-ever carbon credits under the Paris Agreement have been issued to a cookstove project in Myanmar, said Climate Home News.
- SAUDI SOLAR: Turkey has signed a “major” solar deal that will see Saudi firm ACWA building 2 gigawatts in the country, according to Agence France-Presse.
$467 billion
The profits made by five major oil firms since prices spiked following Russia’s invasion of Ukraine four years ago, according to a report by Global Witness covered by BusinessGreen.
Latest climate research
- Claims about the “fingerprint” of human-caused climate change, made in a recent US Department of Energy report, are “factually incorrect” | AGU Advances
- Large lakes in the Congo Basin are releasing carbon dioxide into the atmosphere from “immense ancient stores” | Nature Geoscience
- Shared Socioeconomic Pathways – scenarios used regularly in climate modelling – underrepresent “narratives explicitly centring on democratic principles such as participation, accountability and justice” | npj Climate Action
(For more, see Carbon Brief’s in-depth daily summaries of the top climate news stories on Monday, Tuesday, Wednesday, Thursday and Friday.)
Captured
The constituency of Richard Tice MP, the climate-sceptic deputy leader of Reform UK, is the second-largest recipient of flood defence spending in England, according to new Carbon Brief analysis. Overall, the funding is disproportionately targeted at coastal and urban areas, many of which have Conservative or Liberal Democrat MPs.
Spotlight
Is there really a UK ‘greenlash’?
This week, after a historic Green Party byelection win, Carbon Brief looks at whether there really is a “greenlash” against climate policy in the UK.
Over the past year, the UK’s political consensus on climate change has been shattered.
Yet despite a sharp turn against climate action among right-wing politicians and right-leaning media outlets, UK public support for climate action remains strong.
Prof Federica Genovese, who studies climate politics at the University of Oxford, told Carbon Brief:
“The current ‘war’ on green policy is mostly driven by media and political elites, not by the public.”
Indeed, there is still a greater than two-to-one majority among the UK public in favour of the country’s legally binding target to reach net-zero emissions by 2050, as shown below.
Steve Akehurst, director of public-opinion research initiative Persuasion UK, also noted the growing divide between the public and “elites”. He told Carbon Brief:
“The biggest movement is, without doubt, in media and elite opinion. There is a bit more polarisation and opposition [to climate action] among voters, but it’s typically no more than 20-25% and mostly confined within core Reform voters.”
Conservative gear shift
For decades, the UK had enjoyed strong, cross-party political support for climate action.
Lord Deben, the Conservative peer and former chair of the Climate Change Committee, told Carbon Brief that the UK’s landmark 2008 Climate Change Act had been born of this cross-party consensus, saying “all parties supported it”.
Since their landslide loss at the 2024 election, however, the Conservatives have turned against the UK’s target of net-zero emissions by 2050, which they legislated for in 2019.
Curiously, while opposition to net-zero has surged among Conservative MPs, there is majority support for the target among those that plan to vote for the party, as shown below.
Dr Adam Corner, advisor to the Climate Barometer initiative that tracks public opinion on climate change, told Carbon Brief that those who currently plan to vote Reform are the only segment who “tend to be more opposed to net-zero goals”. He said:
“Despite the rise in hostile media coverage and the collapse of the political consensus, we find that public support for the net-zero by 2050 target is plateauing – not plummeting.”
Reform, which rejects the scientific evidence on global warming and campaigns against net-zero, has been leading the polls for a year. (However, it was comfortably beaten by the Greens in yesterday’s Gorton and Denton byelection.)
Corner acknowledged that “some of the anti-net zero noise…[is] showing up in our data”, adding:
“We see rising concerns about the near-term costs of policies and an uptick in people [falsely] attributing high energy bills to climate initiatives.”
But Akehurst said that, rather than a big fall in public support, there had been a drop in the “salience” of climate action:
“So many other issues [are] competing for their attention.”
UK newspapers published more editorials opposing climate action than supporting it for the first time on record in 2025, according to Carbon Brief analysis.
Global ‘greenlash’?
All of this sits against a challenging global backdrop, in which US president Donald Trump has been repeating climate-sceptic talking points and rolling back related policy.
At the same time, prominent figures have been calling for a change in climate strategy, sold variously as a “reset”, a “pivot”, as “realism”, or as “pragmatism”.
Genovese said that “far-right leaders have succeeded in the past 10 years in capturing net-zero as a poster child of things they are ‘fighting against’”.
She added that “much of this is fodder for conservative media and this whole ecosystem is essentially driving what we call the ‘greenlash’”.
Corner said the “disconnect” between elite views and the wider public “can create problems” – for example, “MPs consistently underestimate support for renewables”. He added:
“There is clearly a risk that the public starts to disengage too, if not enough positive voices are countering the negative ones.”
Watch, read, listen
TRUMP’S ‘PETROSTATE’: The US is becoming a “petrostate” that will be “sicker and poorer”, wrote Financial Times associate editor Rana Forohaar.
RHETORIC VS REALITY: Despite a “political mood [that] has darkened”, there is “more green stuff being installed than ever”, said New York Times columnist David Wallace-Wells.
CHINA’S ‘REVOLUTION’: The BBC’s Climate Question podcast reported from China on the “green energy revolution” taking place in the country.
Coming up
- 2-6 March: UN Food and Agriculture Organization regional conference for Latin America and Caribbean, Brasília
- 3 March: UK spring statement
- 4-11 March: China’s “two sessions”
- 5 March: Nepal elections
Pick of the jobs
- The Guardian, senior reporter, climate justice | Salary: $123,000-$135,000. Location: New York or Washington DC
- China-Global South Project, non-resident fellow, climate change | Salary: Up to $1,000 a month. Location: Remote
- University of East Anglia, PhD in mobilising community-based climate action through co-designed sports and wellbeing interventions | Salary: Stipend (unknown amount). Location: Norwich, UK
- TABLE and the University of São Paulo, Brazil, postdoctoral researcher in food system narratives | Salary: Unknown. Location: Pirassununga, Brazil
DeBriefed is edited by Daisy Dunne. Please send any tips or feedback to debriefed@carbonbrief.org.
This is an online version of Carbon Brief’s weekly DeBriefed email newsletter. Subscribe for free here.
The post DeBriefed 27 February 2026: Trump’s fossil-fuel talk | Modi-Lula rare-earth pact | Is there a UK ‘greenlash’? appeared first on Carbon Brief.
Seven Pacific island nations say they will demand heftier levies on global shipping emissions if opponents of a green deal for the industry succeed in reopening negotiations on the stalled accord.
The United States and Saudi Arabia persuaded countries not to grant final approval to the International Maritime Organization’s Net-Zero Framework (NZF) in October and they are now leading a drive for changes to the deal.
In a joint submission seen by Climate Home News, the seven climate-vulnerable Pacific countries said the framework was already a “fragile compromise”, and vowed to push for a universal levy on all ship emissions, as well as higher fees . The deal currently stipulates that fees will be charged when a vessel’s emissions exceed a certain level.
“For many countries, the NZF represents the absolute limit of what they can accept,” said the unpublished submission by Fiji, Kiribati, Vanuatu, Nauru, Palau, Tuvalu and the Solomon Islands.
The countries said a universal levy and higher charges on shipping would raise more funds to enable a “just and equitable transition leaving no country behind”. They added, however, that “despite its many shortcomings”, the framework should be adopted later this year.
US allies want exemption for ‘transition fuels’
The previous attempt to adopt the framework failed after governments narrowly voted to postpone it by a year. Ahead of the vote, the US threatened governments and their officials with sanctions, tariffs and visa restrictions – and President Donald Trump called the framework a “Green New Scam Tax on Shipping”.
Since then, Liberia – an African nation with a major low-tax shipping registry headquartered in the US state of Virginia – has proposed a new measure under which, rather than staying fixed under the NZF, ships’ emissions intensity targets change depending on “demonstrated uptake” of both “low-carbon and zero-carbon fuels”.
The proposal places stringent conditions on what fuels are taken into consideration when setting these targets, stressing that the low- and zero-carbon fuels should be “scalable”, not cost more than 15% more than standard marine fuels and should be available at “sufficient ports worldwide”.
This proposal would not “penalise transitional fuels” like natural gas and biofuels, they said. In the last decade, the US has built a host of large liquefied natural gas (LNG) export terminals, which the Trump administration is lobbying other countries to purchase from.
The draft motion, seen by Climate Home News, was co-sponsored by US ally Argentina and also by Panama, a shipping hub whose canal the US has threatened to annex. Both countries voted with the US to postpone the last vote on adopting the framework.
-
IMO head: Shipping decarbonisation “has started” despite green deal delay
Arsenio Dominguez said the shipping industry’s net zero emissions goal is not in dispute although countries have stalled on adopting a framework to reach it -
US-led alliance wins a year’s delay in adoption of green shipping deal
The IMO’s Net-Zero Framework will be up for approval again in October 2026, after the US and Saudi Arabia persuaded countries not to vote on it as planned
The IMO’s Panamanian head Arsenio Dominguez told reporters in January that changes to the framework were now possible.
“It is clear from what happened last year that we need to look into the concerns that have been expressed [and] … make sure that they are somehow addressed within the framework,” he said.
Patchwork of levies
While the European Union pushed firmly for the framework’s adoption, two of its shipping-reliant member states – Greece and Cyprus – abstained in October’s vote.
After a meeting between the Greek shipping minister and Saudi Arabia’s energy minister in January, Greece said a “common position” united Greece, Saudi Arabia and the US on the framework.
If the NZF or a similar instrument is not adopted, the IMO has warned that there will be a patchwork of differing regional levies on pollution – like the EU’s emissions trading system for ships visiting its ports – which will be complicated and expensive to comply with.
This would mean that only countries with their own levies and with lots of ships visiting their ports would raise funds, making it harder for other nations to fund green investments in their ports, seafarers and shipping companies. In contrast, under the NZF, revenues would be disbursed by the IMO to all nations based on set criteria.
Anais Rios, shipping policy officer from green campaign group Seas At Risk, told Climate Home News the proposal by the Pacific nations for a levy on all shipping emissions – not just those above a certain threshold – was “the most credible way to meet the IMO’s climate goals”.
“With geopolitics reframing climate policy, asking the IMO to reopen the discussion on the universal levy is the only way to decarbonise shipping whilst bringing revenue to manage impacts fairly,” Rios said.
“It is […] far stronger than the Net-Zero Framework that is currently on offer.”
The post Pacific nations want higher emissions charges if shipping talks reopen appeared first on Climate Home News.
Pacific nations want higher emissions charges if shipping talks reopen
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