Ellie Chowns, Green Party MP for North Herefordshire. CC image Wikipedia.
Responding to the release of detailed proposals for Heathrow Airport expansion, Green Party MP, Ellie Chowns, reiterated the Green Party’s opposition to airport expansion, saying,
These expansion plans are, at their heart, aimed to deliver profit for shareholders to enable a small group of people to fly more and more. In the UK we have a few frequent flyers that make up less than 3% of the UK population but take 30% of all journeys. On top of this, they seem oblivious to the impact that these plans will have on the communities currently living around Heathrow. Government must be grounded in reality and look hard at the climate science. No credible net-zero plan can include rampant airport expansion, and it’s time Labour looked to the many, many alternative ways to create high-paid green jobs.”
Reaching net-zero will be much cheaper for the UK government than previously expected – and the economic damages of unmitigated climate change far more severe.
These are two key conclusions from the latest report on risks to the government finances from the independent Office for Budget Responsibility (OBR), which includes a chapter on climate change.
The new OBR report shows very clearly that the cost of cutting emissions to net-zero is significantly smaller than the economic damages of failing to act.
Here are four key charts from the OBR report.
Climate damages could reach 8% of GDP by 2070s
The UK could take an 8% hit to its economy by the early 2070s, if the world warms by 3C this century, according to the new OBR report.
(This aspect of the OBR report has been picked up in a Reuters headline: “Global 3C warming would hurt UK economy much more than previously predicted, OBR says.”)
Its latest estimate (blue line) of the impact of “climate-related damages” by the 2070s is three percentage points (60%) higher than thought just last year (yellow), as shown in the figure below.
Left: Impact of climate damages on UK GDP, if global warming reaches 3C by the end of the century. Right: Impact on government borrowing. Blue lines show the latest estimates whereas yellow lines are from last year’s report. Credit: OBR
The OBR says that the increase in its estimate of climate damages is due to using a “more comprehensive and up-to-date analysis”.
(The world is currently on track to warm by only slightly less than 3C this century.)
Unchecked damages could double hit to borrowing
The impact of climate damages on government borrowing would be nearly twice as high by the 2070s, if global warming goes unchecked and reaches 3C, according to the OBR report.
This is shown in the figure below, which compares additional government borrowing each year, as a share of GDP, if warming is limited to less than 2C this century (left) or if it climbs to 3C (right).
Additional government borrowing each year due to climate damages, as a share of GDP, %, if warming is limited to less than 2C this century (left) or 3C (right). Credit: OBR.
The OBR explains that the largest impact of climate damages on government borrowing is “lower productivity and employment and, therefore, lower tax receipts”.
Cost of net-zero halved
When it comes to cutting UK emissions, the OBR says the government will only need to invest just over half as much on reaching net-zero, compared with what it expected four years earlier.
This is shown in the figure below, with the latest 2025 estimate (right) showing a cumulative government investment of 6% of GDP across the 25 years to 2050, down from 11% (left).
(Note that the large majority of “lost government receipts”, shown in yellow in the figure below, are due to fuel duty evaporating as drivers shift to electric vehicles. As the OBR notes, the government could choose to recoup these losses via other types of motoring taxes.)
Cumulative change in government lost receipts (yellow) and extra investment (green), as a share of GDP, %. Left: OBR’s 2021 report. Right: Latest 2025 report. Credit: OBR.
The OBR takes its estimates of the costs and benefits of cutting emissions to net-zero from the government’s Climate Change Committee (CCC). The CCC recently issued significantly lower estimates for net-zero investment costs, due to more rapidly falling clean-technology costs.
Acknowledging this shift, the OBR says the latest CCC estimates on the cost of reaching net-zero are “significantly lower” than earlier figures.
It notes that the net cost to the economy of reaching net-zero emissions by 2050 is now put at £116bn over 25 years, some £204bn lower than previously expected.
In very rough terms, this figure – which excludes health co-benefits due to cutting emissions and avoided climate damages – is equivalent to less than £70 per person per year.
Cost of action far lower than cost of inaction
Taken together, the OBR findings show more clearly than ever before that the cost of taking action to tackle climate change would be far lower than the cost of unchecked warming.
For the first time, its latest report combines the estimated cost of cutting emissions with the expected damages due to rising temperatures in a single figure, shown below.
The comparison illustrates that climate damages (blue bars in the chart) are set to impose severe costs on the UK public finances, even if warming is limited to less than 2C this century (left).
The OBR also shows how the cost of government investment in cutting emissions (yellow) is both temporary and relatively small in comparison to climate damages.
Moreover, it highlights how unchecked warming of 3C this century (right) would impose far higher climate damages on the UK government’s finances than if global temperatures are kept in check.
Specifically, global action to limit warming to 2C instead of 3C could prevent more than 1 percentage point of climate damages being added to annual government borrowing by the 2070s.
In contrast, the combined estimated cost to government of action to cut emissions never exceeds 0.6 percentage points – even if lost receipts due to fuel duty are not replaced (green).
Annual additional government borrowing as a result of action to cut emissions (yellow, green) and from climate damages (blue, purple). Left: 2C of warming this century. Right: 3C. Credit: OBR.
Beyond these new numbers, the OBR acknowledges that it still does not include the cost of adapting to climate change, or the impact this could have on reducing damages.
Nor does it consider the potential for accelerated transitions towards clean energy, technological advances that make this shift cheaper or the risk of tipping points, which could cause “large and irreversible changes” to the global climate.
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With average global temperatures set to see another record high this year, the chances of holding warming to no more than 1.5C continue to dwindle.
Keeping warming below 1.5C by the end of the century – in line with the long-term goal of the Paris Agreement – now likely involves “overshooting” 1.5C and then bringing temperatures back down later by removing carbon dioxide (CO2) from the atmosphere.
(What this means for “net-negative” emissions is covered in a previous guest post.)
This raises a number of unknowns in terms of what overshoot means for the impacts of climate change on the planet, people and ecosystems.
For example, even if global temperatures can be brought back down again by the end of the century, will the impacts of climate change also reduce? Will coral reefs be able to recover or will glaciers reform? What will it mean for the world’s coastlines, food production and endangered species?
For the past three years, we have been working on a Horizon Europe-funded project called PROVIDE to dive deeper into what overshoot really looks like for countries, regions and cities.
This data is available on the Climate Risk Dashboard – a tool to help people see how climate change will affect them and how it depends on the actions taken today.
Until carbon emissions are reduced to net-zero, the world will not stop warming. Delay will result in ever more intense climate impacts – and increase the risk of crossing irreversible thresholds.
Urban heat stress under overshoot
One of the clearest and most acute impacts of climate change is on extreme heatwaves. Our findings suggest that, were global average temperatures to decline, extreme heat events in most locations will also decrease, on average.
But achieving a new balance in local climates would be a slow process, influenced by ongoing climate system adjustments for decades – if not centuries – to come.
Reversing climate change would most probably take several decades, even if overshoot is limited to a few tenths of a degree. This implies that the climate risks that generations alive today will be exposed to are largely determined by collective actions today.
We can illustrate these differences for the risks of extreme heat stress for the Indian city of Chennai, one of 140 cities for which we modelled urban heat stress risks at 100-metre spatial resolution.
The chart below shows the projected annual number of days of extreme heat stress in Chennai – defined as days where wet-bulb globe temperature (WBGT) goes over 31C. (WBGT is a metric that combines air temperature, humidity and exposure to direct sunlight.)
This level of heat stress approaches the limits of human survivability (without adaptation) – for example, physical outdoor labour is almost impossible under these conditions.
Under current 2020 climate policies, leading to a best estimate of about 3C of warming in 2100, extreme heat days increase pretty much unchecked. By the end of the century, around half of the days (180) per year would experience extreme heat stress conditions (or even higher).
In contrast, in a 1.5C low-overshoot scenario (the IPCC Shifting Pathway), the number of extreme heat stress days would peak mid-century at around 120 days , before declining again to around 110 days by 2100 as global average temperature decreases from just above 1.5C to around 1.3C. This is a modest decline in extreme heat risk, yet a profound difference from a 3C world.
Projected days a year with extreme heat stress in Chennai from 2020 to 2100 under the climate policies of 2020 (blue) and 1.5C low-overshoot scenario called “IPCC Shifting Pathway” (green). Source: PROVIDE Dashboard
Irreversible consequences from overshoot
There are many other impacts of climate change that will be irreversible – for centuries to millennia – at peak temperatures, let alone if society is able to bring warming back down.
Yet, a lot of these losses can still be avoided by stringent mitigation. For example, our multi-scenario framework allows us to explore glacier futures showing unavoidable, or “locked-in”, risks even under the lowest emission scenario we have explored, and compare them with the avoidable risks through stringent mitigation.
Below, we provide an example for glacier volume projections for Peru, where glaciers serve as an essential freshwater resource during the extremely dry season of June to September. Due to past warming, glacier loss will continue over the coming decades. Under a current policy scenario (blue dots), 50% of the glacier volume might be lost as early as 2050.
Yet this does not need to happen. In fact, stringent mitigation pathways (green dots) are still possible that give a four-in-five chance of preserving 50% of today’s glacier ice in Peru, avoiding the worst and helping to maintain some of their vital uses.
Chart illustrating risks of losing 50% of 2020 glacier volume for Peru today and in 2030, 2050 and 2100, under the climate policies of 2020 (blue) and 1.5C low-overshoot scenario called “IPCC Shifting Pathway” (green). Shading highlights the avoidable risk. Source: PROVIDE Dashboard.
Overshoot risks for the biosphere
Climate change represents a major threat to biodiversity globally. We modelled species at risk from local extinction for about 135,000 terrestrial fungi, plants, invertebrates and vertebrates based on the Wallace Initiative.
Under the assumption that the 1950-2000 reference climate was suitable for the species at question, we model the proportion of species for which the local climate becomes unsuitable under ongoing climate change.
In the chart below, we illustrate the risks to species in one of the countries with the world’s richest terrestrial biodiversity, Brazil. Under the current policy scenario (blue dots), the likelihood of 50% of species being at risk of local extinction rises to 74% by 2100. Yet, our analysis shows that this likelihood can still be avoided almost entirely by stringent mitigation (green dots).
Chart showing the likelihood of 50% of Brazilian species being at risk of local extinction today and in 2030, 2050 and 2100, under the climate policies of 2020 (blue) and 1.5C low-overshoot scenario called “IPCC Shifting Pathway” (green). Shading highlights the avoidable risk. Source: PROVIDE Dashboard.
It is important to highlight that species loss does depend on a range of factors – of which climate suitability is only one. Yet there is a range of other human-caused stressors to biodiversity loss and a complex interdependencies of species and food webs in particular in the most biodiverse ecosystems implies the risk of knock-on effects and ecosystem tipping points.
We also note that our results do not necessarily imply global species extinction and do not allow us to quantify if and how species survival under different overshoot trajectories would emerge.
Overshoot will stress adaptation planning
Overshoot outcomes matter for climate risk assessments. Yet, in contrast with the prominence of overshoot pathways in the climate mitigation literature, their implications for adaptation planning have not been widely explored.
Overshoot would increase the threat of climate change that society needs to adapt to – and make that adaptation more difficult. Some options may become unavailable due to limits of adaptation.
Also, timescales matter. Reversing an overshoot will take decades. Even assuming reversibility of climate hazards in the future as temperatures come down, this might only matter for adaptation decisions that involve a planning horizon of 50 years or more.
This is illustrated in the chart below, from our recent Nature study. This shows a stylised trajectory of warming (top chart) with overshoot (red bars) and how it compares to planning horizons for some example adaptation options (green bars), the lifetime of those measures (blue bars) and the intergenerational equity they involve (bottom chart).
The possibility of reversing long-term impacts in the future does not reduce the urgent need to act now on closing the wide gap in current adaptation efforts.
Figure showing: a) stylised temporal evolution of a reversible climate impact driver under a peak and decline scenario. Dashed lines indicate a low and high overshoot outcome with median timescales of global temperature reversibility typically in line with those from the IPCC AR6 database; and b) stylised illustration of adaptation-relevant timescales starting in 2030, including different planning horizons for adaptation planning (green bars) and lifetimes of individual adaptation measures (blue), and the effect of applying discounting (reflecting societal preferences towards intergenerational equity) to future damages and adaptation benefits. Source: Schleussner et al. (2024)
Limit peak warming and aim for long-term decline
While our results clearly underscore the importance of limiting peak warming to as low as possible, there are also very good arguments for aiming for a long-term global temperature decline, irrespective of the peak warming level.
For a wide range of time-lagged climate impacts, such as ice sheet, peatland and permafrost loss, as well as large-scale irreversible tipping points, achieving temperature decline well below 1.5C is key to limiting long-term risks from global warming.
Overshoot is clearly not an alternative way to achieve a similar climate outcome. Effectively limiting climate risks requires restricting peak warming as low and as close to 1.5C as possible – and then aim for long-term decline to reduce the climate impact legacy of human-caused emissions.
Major disruption to Barclays AGM by Money Rebellion and other activist groups with searching questions, songs and Shakespeare
A major bank funding our extinction by pouring billions of pounds into new fossil fuel projects was left in disarray today as activists linked to a huge new climate crisis coalition disrupted their Annual General Meeting headquarters in the City of London.
The board of directors faced constant interruption and challenge making it almost impossible for the AGM to continue. When Barclays chairman Nigel Higgins tried to outline the bank’s own climate commitments, a protester shouted “bullshit.”
At 11am teams of activists infiltrated the AGM of Europe’s biggest funder of fossil fuels, Barclays. A 70-strong Climate Choir sang a climate crisis version of the Spice Girls “Stop Right Now” to bank board members. Further disruption followed as other shareholders from Fossil Free London, with a Shakespearean condemnation of Barclays as being on the wrong side of history.
Pulling out hidden ruffs and quills, they performed Shakespeare-based lines generated by ChatGPT about the bank’s funding of fossil fuels. Lines included: “The people thee harm, and our air thou pollute! And yet, there is more, I tell you this day, For Barclays is guilty in a vile way. Thou art on the wrong side of history, I say!”
At the action, Claude Fourcroy, of Money Rebellion, an off-shoot of Extinction Rebellion, said: “We need UK banks to stop funding fossil fuels today, but instead they are profiting from a rigged system where bankers sacrifice people and planet to make vast fortunes. This is why we have chosen to target these vastly wealthy and powerful establishments, in the interests of the public – because time for humanity and every other species on the planet is running out.
“These banks boast about being part of the solution to the climate and ecological emergency while taking baby steps toward pulling funding for the worst fossil fuel criminals, making empty promises full of loopholes, and greenwashing on an industrial scale
“The government and Bank of England are failing to challenge or regulate the power of the banks. But people power can and will stop them. No more carbon bombs, no more genocide and no more displacement. Until the banks stop funding new fossil fuels, we will use every tool in the box to stop them, including building the biggest bank boycott in history to hit them where it hurts – in their pockets.”
Extinction Rebellion co-founder Clare Farrell said: “These Money Rebellion actions disrupting financial power holders are just the start of an unprecedented movement of movements stepping up to challenge the corrupt elite in order to drive the urgent changes we need for survival of life on this planet.”
“In this new phase of Extinction Rebellion, we are connecting across groups to build a stronger climate alliance aimed at community resilience, inclusivity and fairness for all living beings. By linking up everyone who stands for a just and rapid response to the climate crisis we will create a formidable opposition. People are determined to challenge the misuse of power which threatens to bring an end to all life if we do not stop it.”
Barclays’ AGM was targeted by activists because the bank is the largest financier of fossil fuel expansion, heavily funding new fossil fuel exploration and drilling, while issuing net zero pledges.
According to Rainforest Action Network and Greenpeace since 2016 Barclays has been the worst bank in Europe for fossil fuel financing. In 2022 alone, the bank provided over $16 billion to coal, oil, and gas companies, and $190 billion since the Paris Agreement, making it the seventh largest fossil fuel funder in the world.
Barclays has said it is committed to aligning its financed emissions with the goals of the Paris Agreement, but in reality the bank has no policy dictating how it should reduce its financing of the oil and gas sector. Barclays is one of the only major UK banks which has not started the process of restricting financing for new oil and gas, putting it at odds with competitors HSBC, Lloyds, and NatWest.
Andrew Taylor from Money Rebellion, an offshoot of Extinction Rebellion, added: “As the UN Secretary General António Guterres has said, we have reached a tipping point on the need for climate action. The disruption to our climate and our planet is already worse than we thought, and it is moving faster than predicted. And what is the reaction of these banks to this frightening scenario?
“According to the London School of Economics and the Grantham Research Institute on Climate Change and the Environment Barclays scores 0% on its commitment to achieve net-zero emissions from its financing activities by 2050 or sooner, consistent with a 1.5°C scenario. It also scores 0% on climate policy engagement.
“A more accurate title for these AGMs would be Annual Greenwash Meetings.”
