What accelerating warming means for climate and wider policy

The acknowledged acceleration in global warming has profound implications, not just for climate policy, but for adaptation, resilience, food security, migration, finance and insurance, net-zero...

It’s now acknowledged that global warming is accelerating. It’s widely reported in scientific papers, state of the climate reports and most recently in an article from the New York Times¹, the source of the chart below. The acceleration is also evident in every other measure of the climate system, not just the commonly cited global average surface air temperature.² The acceleration brings forward the need for policy changes to both deal with the causes of the problem, continued fossil fuel emissions and land use change, and deal with the consequences.

What’s driving the acceleration?

We know the accelerating warming is due to the Earth accumulating energy at an increasing rate. The NASA CERES satellite mission measures the Earth’s Energy Imbalance (EEI), the difference between the incoming solar radiation and the outgoing reflected and radiated energy. An EEI of zero, a perfect balance, means no extra energy is accumulating or being lost, leading to a stable climate. A negative EEI cools the planet as more heat escapes and a positive EEI warms it. The EEI measured by CERES since 2000 shows it steadily increasing, becoming more and more positive. This means the earth is absorbing and accumulating energy at an increasing rate.

The two graphs below show the 36 month smoothed EEI since 2003 on the left and the resulting energy accumulation accelerating on the right.

Where is the accumulating energy going?

The vast majority of the accumulating energy goes towards warming the oceans. This accounts for 91% of the heat. Not surprisingly the ocean heat content is accelerating at all depths. Warm water expands, so this is driving part of the acceleration of sea level rise. The ocean surface is also warming which provides greater evaporation potential and energy for storm systems.

4% of the heat is melting the worlds cryosphere, the mountain glaciers, continental ice sheets and permafrost. Glacier melt is accelerating fast. The world has lost 5.4% of its total glacial volume since 2000. European glaciers lost over 38%³. In just the last 4 years though, the US and Canada lost 12% and Switzerland 13%⁴.

Ice sheet volume in both Greenland and Antarctica is also melting faster. Combined with the glacial melt and thermal expansion this is driving sea level rise at double the rate it was just a few decades ago.⁵

Another 4% of the energy imbalance goes to warming land surfaces. Land areas are warming faster than the global average as a result. Europe is the fastest warming continent and has already warmed more than 2ºC since pre-industrial times.

That leaves just 1% of the energy which goes towards warming the troposphere, the lower atmospheric air. Acceleration is even evident in this tiny proportion as seen in the top graphic from the New York Times article.

Why is it faster than expected?

In building models and making predictions, ranges have to be assigned to the strength of various mechanisms and feedbacks. One of the largest uncertainties has been the cloud response to the warming climate. The 2021 IPCC AR6⁶ report showed a large range of feedback strength from very weakly positive to strongly positive. Forecasts are then made by setting the estimate in the middle of that range. The last few years of data have however shown that the real answer was indeed strongly positive. Cloud fraction, the amount of clouds, and their brightness have both reduced significantly. This has reduced the amount of solar radiation being reflected back into space pushing the EEI up.

In addition it seems that the reduction in human sulphate aerosol pollution has had a stronger effect on cloud properties than was assumed. The combination of warming and pollution reduction efforts have had a big effect, driving a significant proportion of the acceleration.

Other factors are also at play. It was assumed that vegetation would continue to keep up with human CO₂ emissions drawing down a consistent proportion each year. This has unfortunately not been the case. Vegetation sequestration of CO₂ peaked in 2008 and has been in decline ever since. Coupled with increasing human and natural methane and nitrous oxide emissions, this means the atmospheric greenhouse gases are accumulating faster than they have been.

Climate models predicted some acceleration but the measurements are exceeding the expectations. 1.5ºC of warming will be breached in the next few years with years hitting 2ºC early next decade. That’s not to criticise the models. The various feedback loops accelerating the warming are becoming better understood as the data becomes available. To be prudent, the IPCC does not include elements that are not sufficiently understood in its estimates. For example models for AMOC collapse don’t include Greenland ice melt because it was not well enough understood to be coupled to the ocean circulation models. The same is true with ice sheet dynamics and sea level rise, although they do show a low certainty extreme curve as a worse case to cover the unknowns.

Policy Implications

The majority of public policy is based on IPCC predictions (OK, with a notable exception). So with the data now showing faster warming than anticipated, a lot of these policies now need to be urgently updated with a matching acceleration of ambition. Put simply, the impacts that were expected in 2050 if we continued with business as usual, are now likely to happen in the 2030s under business as usual and are still likely to happen before 2050 even under ambitious decarbonisation.

A paper from notable scientists in 2022, including Luke Kemp, Johan Rockstrom and Tim Lenton, looked at the implications and reactions required for catastrophic climate change scenarios. At the time of writing, acceleration was not an issue. Today however, their analysis is very relevant.⁷

Let’s start with the obvious need to update decarbonisation policy.

Decarbonisation and net-zero policy

Each year a set of carbon budgets are produced by Piers Forster and 60 co-authors in the Indications of Global Climate Change report⁸. The report calculates the human emissions, the measured changes to the climate system and importantly, the remaining carbon budget to meet the Paris Agreement goals.

In tacit recognition of the acceleration, the 2025 report shows a significantly greater drop in remaining carbon budget from 2024 than the total human emissions for the year. The 2024 report showed 200Gt remaining for a 50% chance of achieving 1.5ºC while in 2025 the report indicated a remaining 130Gt while reporting just 53Gt of emissions that year.

Whilst the idea that there is any remaining carbon budget at all to even stay below 2ºC is probably wishful thinking⁹, it does show that the trajectories suggested under the various socio-economic pathways are now looking very optimistic indeed, even if we could move the needle towards the sustainable ones.

Acceleration means net-zero by 2050 is simple not good enough to avoid the disastrous impacts of rapid climate change. The apparent strength of feedback effects such as cloud albedo reduction, aerosol reductions both natural and human caused, ocean circulation changes such as the recently discovered surface salination of the Southern Ocean leading to decreased sea ice cover¹⁰, the lowering of the permafrost tipping element threshold¹¹, and so on, mean that warming is set to continue accelerating until we meaningfully reduce our emissions.

Accelerating also means that tipping elements within the climate system move closer in the future, increasing the risk of un-recoverable changes that would have huge impacts on the world. The recent Global Tipping Points Conference in Exeter ended with a statement to global leaders to take “immediate, unprecedented action” to prevent devastating climate tipping points.¹²

Policies to ban new fossil fuel vehicles and gas boilers, to revolutionise agriculture and land-use changes, minimise plastic waste including in fast fashion and so on, now need to be brought forward, not pushed back.

Overshoot is a term used in many climate policies and refers to exceeding the Paris goals but returning below them by the end of the century through carbon removal strategies. The burden being put on these strategies, both natural and technological is increasing with acceleration. They will have to draw down a lot more carbon a lot quicker than anticipated. Development, investment and scaling therefore needs to be dramatically increased and brought forward.

Adaptation and resilience building

Assuming decarbonisation doesn’t happen at the pace required, adaptation measures and resilience building becomes a growing priority. Depending on the regional risks, this could include moving communities away from flood plains and likely areas of coastal erosion. It could mean changing building regulations to make houses more suitable for heatwaves, it could mean urban planting schemes to provide shade and reduce urban heat island effects. It should certainly include disaster preparations potentially including drills both for the public and emergency services. Pre-Covid, the UK government assessed the risk of a disease outbreak at 4% in any one year. They conducted emergency medical drills and stockpiled supplies on that basis. The chances of a mass casualty heatwave in Europe is much greater than that, but with completely different stresses and risks to emergency and medical personnel - what plans are being made today I wonder?

Management of water resources and planning for supply chain disruptions could be important for many regions, even rich countries. People in the west go ape-s**t if their Deliveroo is 20 minutes late. What happens when entire crops fail, food prices skyrocket or even if domestic water is rationed?

Adaptation can only go so far though, especially when it comes to extreme heat and drought. Mass deaths from heat exposure have already happened. Droughts are leading to wild animal culling for food in Africa and elsewhere and migration is increasing.

Migration and national security

Assuming decarbonisation and adaptation don’t happen everywhere or at the pace required, migration pressure and national security become ever more serious issues.

A new paper by Eelco Rohling in Oxford Open Climate Change spells it out in very clear terms.¹³

The combination of temperature increases and extremes, drought, and desertification, also linked to food insecurity will drive huge populations out of the tropics and sub-tropics to higher latitudes.

Rather than summarise and risk not doing justice to the paper here are some extracts:

At +4°C global warming, equatorial regions will be largely uninhabitable, especially throughout Africa and Asia. In terms of population numbers affected, the impact is enormous: up to 0.7 billion people will be under very high heat stress in the tropics at +3°C warming, rising to 1.7 billion people at +4°C warming. This means that up to 20% of the world population will be desperate to move away from unliveable conditions. Coming from the tropics, most of them will first enter the subtropics, where drought awaits them.

Intensification of subtropical drought and desertification will play havoc with the world’s food security. The damage will be irreparable unless there is major intervention, which needs to start immediately if we are to re-establish vegetation, increase water-retention, and re-build soils. If not, people throughout subtropical regions will face widespread water shortage, hunger, and all associated side-effects, including conflict and diseases. Yet, at the same time, there will be an influx of vast numbers of people escaping from increasingly unliveable tropical regions. These effects combined form a volatile mix of key drivers for international mass-migration.

The mid- to high-latitude destination regions for people displaced from the tropics and subtropics already contain a high density of people, especially in the northern hemisphere. Yet, these regions cannot cover the loss of tropical-subtropical food production, and global marine food production is also set to decline sharply with ongoing warming. Therefore, a catastrophic cocktail is brewing of desperate mass-migration from lower to higher latitudes, along with a major threat to global food security.

The scale of the migration problem is staggering. 20% of humanity already suffered droughts in 2022 and 2023 (1.8 billion people). 600 million are under severe migration pressure with 30 million already on the move. This will increase by between 3 and 7 times depending on the level of warming, so at least 5 times. That’s 3 billion people. Compare that to the Syrian civil war which saw (only) 6.7 million refugees leave Syria triggering a ‘refugee crisis’ in Europe.

Quite how higher latitude countries prepare policies for this inevitable outcome is beyond me, but I don’t think building the odd wall or setting up visa quotas will cut it. Even feeding this number of people in temporary camps will put huge strain on the food system which will be reeling from crop productivity reductions anyway.

The Exodus Equator: one billion on the move by 2050 report published in 2024, backs up these conclusions but does suggest some ways forward.¹⁴

Financial security and insurability

Just the costs of the migration crisis could easily rise to 1 trillion dollars a year, not including the adaptation costs where practical and the inevitable costs associated with loss and damage, conflict and food insecurity driven economic losses. GDP as we know it today faces massive impacts and with it the consumer led growth that current economies rely on.

The banks are already accepting that +3ºC is inevitable and rather optimistically are hoping this will form the basis of a surge in air conditioning sales. It’s going to be bit more serious than that though.

Two studies on macroeconomic impacts published last year show GDP reduction of up to 29% by 2050 relative to a baseline with no climate impacts.¹⁵ The second paper shows an actual drop of 12% over the next 1ºC of warming.¹⁶

One of the most vulnerable sectors is insurance. Home and infrastructure insurance costs are rising at about 30% a year. You’ll have noticed that with your last renewal. That’s if you are lucky enough to be able to get a quote. These cost increases are going up due to the cost of re-insurance, the insurance that your insurance company takes out in case they get a lot of claims. As more and more expensive disasters like floods, wildfires and hurricanes pile up, eventually a tipping point is reached where insurance becomes insolvent and the costs are just unaffordable. That’s bad enough, but you can’t get a home or business loan if the assets are not insured. The housing market collapses as a result and commercial investment takes a nose dive. This is not a temporary liquidity issue like the 2008 financial crisis. This is caused by a worsening physical reality that can’t be avoided.

The resulting financial shock will be profound, permanent and catastrophic, just when migration pressures are at their peak.

A Boston Consulting Group & Cambridge University report highlighted the difference between 2º and 3ºC calling for rapid and sustained investment to minimise economic damages in the future.¹⁷

Policy choices to deal with this are again beyond me. But society needs to be considering this. Past history tells us we can’t leave it to the banks to manage. We need to find a way of bending, not breaking, the whole basis of international economics and trade and consider how to gracefully manage significant and sustained shrinking of national and international markets and GDP.

Geoengineering

Set against these risks, the risks of geoengineering seem minor. Because of this, people will start to discuss and eventually demand that governments do something about the rising temperatures. Technologies like Stratospheric Aerosol Injection will become more and more attractive as a means of cooling the planet, despite the additional risks.

It’s therefore very important that these techniques are researched (not deployed) so that the risks and benefits are better understood. This is underway in the UK, which I support.¹⁸ Other states that are trying to ban even research may need to re-think this policy.

Conclusions

When I set about writing this article, I must admit that I didn’t think it would be as doom ridden as it turned out to be. The research and thinking through the implications have led to this conclusion however. For this I apologise, but forewarned is forearmed.

The accelerating global warming is real and we can’t avoid what that means or what we must try to do to mitigate it and adapt to the consequences.

Efforts need to be made to decarbonise our societies as fast as possible, faster than all the current government commitments and strategies. At the moment we are choosing to fail even against weak, largely ineffectual, targets.

Adaptation and resilience building investment, which has been a small fraction of even the mitigation spending, needs to be accelerated hugely and targeted towards where it can be most effective. Adaptation investments in tropical and subtropical regions that could reduce migration pressure in the future could be hugely beneficial for everyone.

Plans and strategies need to be developed to deal with human migration on a scale never seen or imagined before. Dealing with and finding ways to avoid regional and wider conflict are also likely to become very pressing.

The financial markets and the basis of trade are under threat. How do we deal with and cope with inevitable de-growth - a lovely soft sounding term for sustained and catastrophic recession? What’s our fallback when insurance is not longer affordable?

The temptation of geoengineering solutions will become irresistible to some, and imposed on us all. Developing the knowledge and also the regulation and control of these approaches is highly important at this stage. We shouldn’t just try and ban it and stick our heads in the sand. It may be the only lifeline for ourselves and nature as we know it.

There will be more and more tragedies along the way, this is unavoidable. While I’m writing this, children's bodies are still being found in Texas after the flash flood. This is obviously a tragedy, but people need dramatic examples to shake them out of apathy.

1. The New York Times, The World Is Warming Up. And It’s Happening Faster. June 26th 2025 https://www.nytimes.com/2025/06/26/climate/climate-heat-intensity.html

2.

3. The GlaMBIE Team. Community estimate of global glacier mass changes from 2000 to 2023. Nature 639, 382–388 (2025). https://doi.org/10.1038/s41586-024-08545-z

4. Menounos, B., Huss, M., Marshall, S., Ednie, M., Florentine, C., & Hartl, L. (2025). Glaciers in Western Canada‐conterminous US and Switzerland experience unprecedented mass loss over the last four years (2021–2024). Geophysical Research Letters, 52, e2025GL115235. https://doi.org/10.1029/2025GL115235

5.

6. IPCC Sixth Assessment Report Working Group 1: The Physical Science Basis, 2021 https://www.ipcc.ch/report/ar6/wg1/

7. Luke Kemp et al. Climate Endgame: Exploring catastrophic climate change scenarios, PNAS, 2022,119 (34) e2108146119,https://doi.org/10.1073/pnas.2108146119

8. Piers Forster et al. Indicators of Global Climate Change 2024: annual update of key indicators of the state of the climate system and human influence, Earth Syst. Sci. Data, 17, 2641–2680, 2025 https://doi.org/10.5194/essd-17-2641-2025

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10. Alessandro Silvano et al. Rising surface salinity and declining sea ice: A new Southern Ocean state revealed by satellites, 2025, PNAS 122 (27) e2500440122 https://doi.org/10.1073/pnas.2500440122

11. Vaks, A., Mason, A., Breitenbach, S.F.M. et al. Arctic speleothems reveal nearly permafrost-free Northern Hemisphere in the late Miocene. Nat Commun 16, 5483 (2025). https://doi.org/10.1038/s41467-025-60381-5

12. https://news.exeter.ac.uk/faculty-of-environment-science-and-economy/tipping-points-experts-issue-urgent-message-to-world-leaders/

13. Eelco J Rohling, Editorial: The migration storm on the horizon, Oxford Open Climate Change, 2025;, kgaf019, https://doi.org/10.1093/oxfclm/kgaf019

14. Exodus Equator: One Billion on the move by 2050, 2024 https://jonathonporritt.com/wp-content/uploads/2024/10/Exodus-Equator-1.pdf

15. Kotz, M., Levermann, A. & Wenz, L. The economic commitment of climate change. Nature628, 551–557 (2024). https://doi.org/10.1038/s41586-024-07219-0

16. Adrien Bilal & Diego R. Känzig, 2024. "The Macroeconomic Impact of Climate Change: Global vs. Local Temperature," NBER Working Papers 32450, National Bureau of Economic Research, Inc.

17. https://web-assets.bcg.com/a1/fc/811b182f481fbe039d51776ec172/landing-the-economic-case-for-climate-action-with-decision-makers-wo-spine-mar-2025.pdf

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