Proceedings of the National Academy of Sciences (PNAS)

Chi Xu, Timothy A. Kohler, and Marten Scheffer

Contributed by Marten Scheffer, October 27, 2019 (sent for review June 12, 2019; reviewed by Victor Galaz and Luke Kemp)

May 4, 2020 117 (21) 11350-11355 https://doi.org/10.1073/pnas.1910114117

Significance

We show that for thousands of years, humans have concentrated in a surprisingly narrow subset of Earth’s available climates, characterized by mean annual temperatures around ∼13 °C. This distribution likely reflects a human temperature niche related to fundamental constraints. We demonstrate that depending on scenarios of population growth and warming, over the coming 50 y, 1 to 3 billion people are projected to be left outside the climate conditions that have served humanity well over the past 6,000 y. Absent climate mitigation or migration, a substantial part of humanity will be exposed to mean annual temperatures warmer than nearly anywhere today.

Abstract

All species have an environmental niche, and despite technological advances, humans are unlikely to be an exception. Here, we demonstrate that for millennia, human populations have resided in the same narrow part of the climatic envelope available on the globe, characterized by a major mode around ∼11 °C to 15 °C mean annual temperature (MAT). Supporting the fundamental nature of this temperature niche, current production of crops and livestock is largely limited to the same conditions, and the same optimum has been found for agricultural and nonagricultural economic output of countries through analyses of year-to-year variation. We show that in a business-as-usual climate change scenario, the geographical position of this temperature niche is projected to shift more over the coming 50 y than it has moved since 6000 BP. Populations will not simply track the shifting climate, as adaptation in situ may address some of the challenges, and many other factors affect decisions to migrate. Nevertheless, in the absence of migration, one third of the global population is projected to experience a MAT >29 °C currently found in only 0.8% of the Earth’s land surface, mostly concentrated in the Sahara. As the potentially most affected regions are among the poorest in the world, where adaptive capacity is low, enhancing human development in those areas should be a priority alongside climate mitigation.

Global warming will affect ecosystems as well as human health, livelihoods, food security, water supply, and economic growth in many ways (1, 2). The impacts are projected to increase steeply with the degree of warming. For instance, warming to 2 °C, compared with 1.5 °C, is estimated to increase the number of people exposed to climate-related risks and poverty by up to several hundred million by 2050. It remains difficult, however, to foresee the human impacts of the complex interplay of mechanisms driven by warming (1, 3). Much of the impact on human well-being will depend on societal responses. There are often options for local adaptations that could ameliorate effects, given enough resources (4). At the same time, while some regions may face declining conditions for human thriving, conditions in other places will improve. Therefore, despite the formidable psychological, social, and political barriers to migration, a change in the geographical distribution of human populations and agricultural production is another likely part of the spontaneous or managed adaptive response of humanity to a changing climate (5). Clearly there is a need to understand the climatic conditions needed for human thriving. Despite a long and turbulent history of studies on the role of climate, and environment at large, on society in geography and beyond (6), causal links have remained difficult to establish, and deterministic claims largely refuted, given the complexities of the relationships in question (7). Rather than reentering the murky waters of environmental determinism (8, 9), here we take a fresh look at this complex and contentious issue. We mine the massive sets of demographic, land use, and climate information that have become available in recent years to ask what the climatic conditions for human life have been across the past millennia, and then examine where those conditions are projected to occur in the future.

Results

Current and Past Human Association to Climate.

Our results reveal that today, humans, as well as the production of crops and livestock (Fig. 1 A, D, and E), are concentrated in a strikingly narrow part of the total available climate space (Fig. 1G). This is especially true with respect to the mean annual temperature (MAT), where the main mode occurs around ∼11 °C to 15 °C (SI Appendix, Fig. S1). By contrast, much of range of precipitation available around that temperature (Fig. 1G and SI Appendix, Fig. S1) is used, except for the driest end. Soil fertility does not seem to be a major driver of human distribution (Fig. 1H), nor can potential productivity be a dominant factor, as net primary productivity shows a quite different geographical distribution (Fig. 1I), peaking in tropical rainforests, which have not been the main foci of human settlement.

Strikingly, the apparent conditions for human thriving have remained mostly the same from the mid-Holocene until now (Fig. 1 A–C). Reconstructions of human distribution and climate are relatively reliable for the past centuries, but uncertainty inevitably increases as we go further back in time. Nonetheless, the two independent sets of available reconstructions we analyzed suggest that as far back as 6000 y BP, humans were concentrated in roughly the same subset of the globally available temperature conditions (Fig. 1C and 2A), despite people at the time living quite differently from today, mostly in the early phases of agriculture or as hunter-gatherers. Historical contingency (including path dependence) may play some role in the inertia we observe, especially when it comes to the sites of economic dominance. However, such economic hotspots occur at somewhat colder conditions than the center of the population distributions (Fig. 1F vs. Fig. 1A), and explaining such patterns of economic dominance requires unraveling the dynamics of historical, cultural, and institutional settings (10–14), which is beyond the scope of this paper.

If we focus at the global distribution of population densities and examine how this codeveloped with climate over time, the precipitation niche turns out to have broadened over the past centuries (Fig. 1A vs. Fig. 1B), leaving only the driest part of the gradient unoccupied (Fig. 1A vs. Fig. 1G). In contrast, the human population distribution in relation to MAT has remained largely unaltered (Fig. 2A), with a major mode around ∼11 °C to 15 °C accompanied by a smaller secondary mode around ∼20 °C to 25 °C corresponding largely to the Indian Monsoon region (SI Appendix, Fig. S2). In the remainder, we focus on this realized temperature niche. Results for the combined precipitation–temperature niche are presented for comparison in the SI Appendix.

Projected Change.

The historical inertia of the human distribution with respect to temperature (Fig. 2) contrasts sharply to the shift projected to be experienced by human populations in the next half century, assuming business-as-usual scenarios for climate (Representative Concentration Pathway 8.5 [RCP8.5]) and population growth (socioeconomic pathway 3 [SSP3]) in the absence of significant migration (Fig. 2A, red curve). Absent climate mitigation or human migration, the temperature experienced by an average human is projected to change more in the coming decades than it has over the past six millennia (Fig. 2B; for different scenarios of population growth and climate change, see SI Appendix, Fig. S3). Compared with the preindustrial situation 300 y BP, the mean human-experienced temperature rise by 2070 will amount to an estimated 7.5 °C, about 2.3 times the mean global temperature rise, a discrepancy that is largely due to the fact that the land will warm much faster than the oceans (2), but also amplified somewhat by the fact that population growth is projected to be predominantly in hotter places (SI Appendix, Fig. S3).

One way to get an image of the temperatures projected to be experienced in highly populated areas in 2070 is to look at the regions where comparable conditions are already present in the current climate. Most of the areas that are now close to the historically prevalent ∼13 °C mode will, in 50 y have a MAT ∼20 °C, currently found in regions such as North Africa, parts of Southern China, and Mediterranean regions (SI Appendix, Fig. S4). Meanwhile, populations in regions that are currently hot already will grow to represent a major part of the global population (right-hand mode of the red curve in Fig. 2A; the role of population growth can be seen in SI Appendix, Figs. S5–S7). Those growing populations will experience MATs currently found in very few places. Specifically, 3.5 billion people will be exposed to MAT ≥29.0 °C, a situation found in the present climate only in 0.8% of the global land surface, mostly concentrated in the Sahara, but in 2070 projected to cover 19% of the global land (Fig. 3).

Another way to quantify change is through following the movement of the geographical location of the human temperature niche (Fig. 4 and SI Appendix, Figs. S8 and S9). For the RCP8.5 climate change scenario (2), the projected geographical shift of favorable conditions over the coming 50 y is substantial (Fig. 4). Indeed, the movement of the niche on the global map is larger than it has been since 6000 BP (SI Appendix, Figs. S8 and S9). These results are robust for different reconstructions of past climate, different approaches to projection of future climate (SI Appendix, Fig. S9), and different versions of the ArchaeoGlobe land use reconstructions. Adding precipitation as an additional climate dimension refines the pattern, mostly by excluding deserts, but leaves the overall picture the same (SI Appendix, Fig. S10). The bottom line is that over the coming decades, the human climate niche is projected to move to higher latitudes in unprecedented ways (SI Appendix, Fig. S11). At the same time, populations are projected to expand predominantly at lower latitudes (SI Appendix, Fig. S5), amplifying the mismatch between the expected distribution of humans and the climate.

A Hypothetical Redistribution.

As conditions will deteriorate in some regions, but improve in other parts (Fig. 4C and SI Appendix, Figs. S9 and S10), a logical way of characterizing the potential tension arising from projected climate change is to compute how the future population would in theory have to be redistributed geographically if we are to keep the same distribution relative to temperature (methods and detailed results in the SI Appendix, Material). Such a calculation suggests that for the RCP8.5 business-as-usual climate scenario, and accounting for expected demographic developments (the SSP3 scenario [15]), ∼3.5 billion people (roughly 30% of the projected global population; SI Appendix, Fig. S12) would have to move to other areas if the global population were to stay distributed relative to temperature the same way it has been for the past millennia (SI Appendix, Fig. S13). Strong climate mitigation following the RCP2.6 scenario would substantially reduce the geographical shift in the niche of humans and would reduce the theoretically needed movement to ∼1.5 billion people (∼13% of the projected global population; SI Appendix, Figs. S12 and S13). Obviously, different scenarios of population growth also have substantial effects on the absolute estimates of potential migration (SI Appendix, Table S3). Such niche movement estimates allow quantifying the implications of global warming in nonmonetary terms. For instance, accounting for population growth projected in the SSP3 scenario, each degree of temperature rise above the current baseline roughly corresponds to one billion humans left outside the temperature niche, absent migration (SI Appendix, Fig. S14).

Discussion

The transparency of our approach is appealing, but inevitably implies some loss of nuance. For instance, temperature captures only part of the relevant climate (16), and potentially important drivers of human thriving are linked in complex ways to climate (13). Importantly, while our projection of the geographical shift of the temperature niche is illustrative, it cannot be interpreted as a prediction of migration, as many factors other than climate affect decisions to migrate, and much of the migration demand may potentially be addressed through climate adaptation (5, 17, 18). Those complexities invite reflections on two key questions: First, how could the narrow realized temperature niche be explained? Second, what are the implications in terms of potential future migration in response to geographical displacement of the temperature niche?

The Question of Causality.

Why have humans remained concentrated so consistently in the same small part of the potential climate space? The full complex of mechanisms responsible for the patterns is obviously hard to unravel. The constancy of the core distribution of humans over millennia in the face of accumulating innovations is suggestive of a fundamental link to temperature. However, one could argue that the realized niche may merely reflect the ancient needs of agrarian production. Perhaps, people stayed and populations kept expanding in those places, even if the corresponding climate conditions had become irrelevant? Three lines of evidence suggest that this is unlikely, and that instead human thriving remains largely constrained to the observed realized temperature niche for causal reasons.

First, an estimated 50% of the global population depends on smallholder farming (19), and much of the energy input in such systems comes from physical work carried out by farmers, which can be strongly affected by extreme temperatures (20). Second, high temperatures have strong impacts (21–23), affecting not only physical labor capacity but also mood, behavior, and mental health through heat exhaustion and effects on cognitive and psychological performance (20, 24, 25). The third, and perhaps most striking, indication for causality behind the temperature optimum we find is that it coincides with the optimum for economic productivity found in a study of climate-related dynamics in 166 countries (12). To eliminate confounding effects of historical, cultural, and political differences, that study focused on the relation within countries between year-to-year differences in economic productivity and temperature anomalies. The ∼13 °C optimum in MAT they find holds globally across agricultural and nonagricultural activity in rich and poor countries. Thus, based on an entirely different set of data, that economic study independently points to the same temperature optimum we infer.

Altogether, it seems plausible that the historically stable association between human distribution and temperature reflects a causal link rather than a legacy, contingent on ancient patterns reflecting agrarian needs or still-more-ancient hunter-gatherer preferences. This supports the view that the historically stable and tight relationship of human distribution to MAT represents a human temperature niche reflecting fundamental constraints on human populations.

Migration as a Possible Response to Climate Change.

Obviously, our hypothetical redistribution calculations cannot be interpreted in terms of expected migration. First of all, detailed regional studies suggest that migration responds nonlinearly to temperature (18, 26, 27). Thus, migration may speed up only when a critical climate threshold is reached. More generally, migration decisions tend to be avoided and depend on a complex array of factors including adaptation options (5, 17, 18). This implies that realized migration numbers will likely be much lower than suggested by the discrepancy between the expected location of the temperature niche and actual distributions of population, even though we have not considered several drivers that could exacerbate movements, such as extreme weather events or projected sea-level rise, which may by themselves lead to substantial population displacements worldwide (28, 29).

Clearly, projections of the magnitude of climate-driven future migration (including asylum seeking) will remain highly uncertain. Even seemingly straightforward links between climate and recent conflicts and migration waves are contentious. For instance, in the years leading up to the current Syrian exodus, the fertile crescent has likely been experiencing the worst drought in 900 y, making subsistence farming in the countryside extremely hard and driving millions in Syria to the cities, where tensions increased (30). However, as many factors play a role, assessing the relative role of climate in such specific conflict or mass migration events always remains challenging (31, 32). This is not to say that there is no evidence for a causal relationship between conflicts and climate events such as prolonged droughts, both now (33) and in the past (34). In fact, the literature is replete with evidence for ancient episodes of climate-triggered human migration and upheaval (e.g., refs. 34–40). For instance, the coldest phase of the Little Ice Age in Europe (1560 to 1660 AD) has been causally linked to a peak of migration (1580 to 1650 AD) and a European population collapse to a minimum in 1650 AD (41). Earlier, the Late Antique Little Ice Age from 536 to about 660 AD affected most of the Northern Hemisphere, likely contributing to the transformation of the Roman Empire, movements out of the Asian steppe and Arabian Peninsula, spread of Slavic-speaking peoples, and upheavals in China (40). Clearly, lessons from such ancient dynamics cannot be directly extrapolated to modern times. However, while outcomes are context dependent, and confounding social, cultural, and political considerations are always present, a range of analyses suggests that changes of climatic conditions can exert enough stress to trigger migration (5, 17, 18, 42), part of which can take the form of asylum-seeking waves in response to climate-driven conflicts (43).

It thus seems reasonable to assume that at least part of the discrepancy caused by the projected geographical shift in the human temperature niche could be reduced through different forms of migration. However, it remains impossible at this point to foresee the extent of climate-driven redistribution of the human population. Technoeconomic scenarios, political developments, institutional changes, and socioeconomic conditions that affect adaptation options may profoundly affect outcomes in ways that will be worth exploring in further scenario analyses utilizing the different assumptions underlying the SSPs. Also, rising mortality impacts of heat waves on dense populations in already-hot places such as India invite further scrutiny (44). Follow-up work is needed to search for integrative avenues for effective adaptation, as well as defining fundamental limitations to what is possible given available resources.

Outlook.

In summary, our results suggest a strong tension between expected future population distributions and the future locations of climate conditions that have served humanity well over the past millennia. So far, the scope for local adaptation has been the dominant focus for analyses of possible responses to a changing climate (4), despite a striking lack of realized adaptation in most regions (12, 13). It is not too late to mitigate climate change and to improve adaptive capacity, especially when it comes to boosting human development in the Global South (45, 46). However, our approach naturally raises the question of what role redistribution of populations may come to play. Migration can have beneficial effects to societies, including a boost to research and innovation (47). However, on larger scales, migration inevitably causes tension, even now, when a relatively modest number of ∼250 million people live outside their countries of birth (48). Looking at the benefits of climate mitigation in terms of avoided potential displacements may be a useful complement to estimates in terms of economic gains and losses.

Methods

We characterized the human climate niche using global gridded datasets for human population as well as a range of social and environmental variables. We used the current population data as well as reconstructed population data available from the History Database of the Global Environment (HYDE 3.1) (49). For early periods, these population data are hindcast from multiple sources. For mid-Holocene, we therefore complement the HYDE data with a reconstruction described in the SI Appendix and based on direct estimates from archaeology (50). Details on the sources and preprocessing of data on crop production, livestock distribution, gross domestic product, and past and present MAT and mean annual precipitation (MAP) are also presented in the SI Appendix. We plotted heat maps illustrating the past and current human climate niche by calculating the mean population density and other variables within each MAT and MAP combination bin and smoothing the result, excluding bins with sparse data points. We also present running means of relevant variables separately against MAT and MAP in the SI Appendix. Uncertainties were characterized as the fifth and 95th percentiles, using different population and climate datasets (SI Appendix).

We modeled the realized human temperature niche based on double-Gaussian fitting of the running mean of the current population distribution against MAT (Fig. 2A, blue dashed curve). We then projected the modeled niche to the past (6 Ky BP) and future (2070) climate conditions (under different Intergovernmental Panel on Climate Change RCPs) to illustrate the potential geographic shift of human temperature niche under near-future global warming. To test for the robustness against adding precipitation as an additional dimension of human climate niche, we also projected the smoothed human distribution in terms of MAT and MAP to the past and future climates for comparison.

To quantify the projected shift of the human temperature niche, we calculated proportions of summed niche gain or loss. By multiplying the projected world’s total population (under different IPCC SSPs) by the proportion of displaced niche, we estimated the numbers that would potentially be displaced if the probability distribution over temperatures were to remain unchanged by 2070.

A detailed description of our materials and methods may be found in the SI Appendix, where the reader may also find a broad set of additional results and sensitivity analyses, as well as a Dryad link to the data used and scripts for all computations.

Acknowledgments

We thank Els Weinans and Shuqing Teng for assistance in data processing and code checking. We also thank Andrew Gillreath-Brown, Henry Wright, Pablo Marquet, and Jennifer Dunne for insightful discussions at the Santa Fe Institute, and Neil Adger for insightful comments on the challenge of foreseeing migration dynamics. This work was partly funded by the National Key R&D Program of China (Grant 2017YFC0506200 to C.X.), the National Natural Science Foundation of China (Grant 31770512 to C.X.), the European Research Council Advanced Grant and Spinoza award (to M.S.), and a Santa Fe Institute Working Group on The Human Niche (to T.A.K. and M.S.). T.A.K. acknowledges support from the US National Science Foundation Grant SMA-1637171. T.M.L.’s contribution was supported by the Leverhulme Trust (Grant RPG-2018-046) and the Alan Turing Institute, through a Turing Fellowship. J.-C.S. considers this work a contribution to his VILLUM Investigator project “Biodiversity Dynamics in a Changing World” funded by VILLUM FONDEN (Grant 16549).

https://www.pnas.org/doi/full/10.1073/pnas.1910114117

David Spratt posed the question Monday 27 July, 2026:

Could Four Billion People Die at 3°C?

The claim that four billion people could die in a 3°C warmer world has become a powerful climate narrative. But what does the science actually support, and where does evidence end and speculation begin?

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David’s purpose was to debunk the exaggeration of deaths, but what I find to be a clear take-away is that masses of people will be adapting to an overheating world by fleeing those hottest places, heading to cooler regions. I recommend reading the entire article here, but if you want to get to the bottom line as I see it … read on below.

The world at 3°C

In a 3°C hotter world, large parts of the tropics will suffer “near-unlivable” extreme heat conditions, there will be less rainfall over significant parts of the dry subtropics, and this combined with increased evaporation rates will lead to drying out and desertification across the dry subtropics. New extremes — of rainfall and heat, flooding and drought — beyond human experience and beyond model expectations will occur. And a committed sea-level rise of many metres will be in the slow process of inundating coastal cities and deltas.

Some research, which is contested, suggests 3°C could cut global GDP by half. Last year, Australian researchers concluded that at 3°C, by the end of the century, the estimated harm to the global economy would be 40%, which “could devastate livelihoods in large parts of the world”.  Coral reef systems would be gone, and that alone means coastal ecosystems would only be able to provide 20–50% of the fish protein that they do today for half a billion people around the world.

In 2021, the Australian Academy of Science published a report co-authored by David Karoly on Risks to Australia of a 3-degree warmer world. Amongst other things, it said that at 3°C, heatwaves would happen as often as seven times a year, with events lasting 16 days on average, “fire risk (driven by record heat, dryness and fuel) will increase by 30 per cent or more in south-eastern Australia”, and yields of key crops would reduce “by between 5 and 50%, depending on crop and location”.  Other research estimates that “beyond 2°C warming, the declines in suitable areas for the 30 crops [analysed] become more pronounced – in some cases approaching and passing 50%”.  That in itself would cause global chaos.

A 2020 study on extreme heat found that at 2.7°C, up to 3.5 billion people will be exposed to temperatures outside the “human niche”, that is, the climate conditions that have served humanity well over the past 6000 years. Further research published in 2023 described a zone of near unlivable heat, “a situation found in the present climate only in 0.8% of the global land surface, mostly concentrated in the Sahara, but in 2070 projected to cover 19% of the global land” (Figure 3). Prof. Marten Scheffer said those pushed outside the climate niche might consider migrating to cooler places: “Not just migration of tens of millions of people but it might be a billion or so.”

And at 2.7°C, scientists say that  the Arctic would be “transformed beyond contemporary recognition: the Arctic Ocean would be essentially ice free for several months in summer, the area of Greenland that reaches melting temperatures for at least a month would roughly quadruple, and the area of permafrost would be roughly half of what it was in preindustrial times.”

Potsdam Institute Director Prof. Johan Rockstrom says that such a level of warming is “something that humanity has absolutely no evidence that we can cope with… Push ourselves to 2.5°C – we’re in unknown terrain. It would lead to a complete melting of the big ice sheets, which would be a 10-metre sea level rise… There would be a collapse of all the big biomes on planet Earth – the rainforest, many of the temperate forests – abrupt thawing of permafrost, we will have complete collapse of marine biology, we will have a shift of large parts of the habitability on Earth.”

Twenty years ago, a group of US security analysts constructed a 3°C scenario:

“Massive nonlinear events in the global environment give rise to massive nonlinear societal events. In this scenario, nations around the world will be overwhelmed by the scale of change and pernicious challenges, such as pandemic disease. The internal cohesion of nations will be under great stress, including in the United States, both as a result of a dramatic rise in migration and changes in agricultural patterns and water availability. The flooding of coastal communities around the world, especially in the Netherlands, the United States, South Asia, and China, has the potential to challenge regional and even national identities. Armed conflict between nations over resources, such as the Nile and its tributaries, is likely and nuclear war is possible. The social consequences range from increased religious fervour to outright chaos. In this scenario, climate change provokes a permanent shift in the relationship of humankind to nature’ (emphasis added).”

So how many would die, and how many would survive in this 3°C world?

Displacement and mortality

The “human niche” papers on near-unliveable heat found that these extremes are projected to envelop 1.2 billion people in India, 485 million in Nigeria and more than 100 million in each of Pakistan, Indonesia and Sudan. Many would be forced to move to a more liveable climate. Another study from the same year of 2020 concluded that warming of 2°C could provide more than 500 million people additional incentive to emigrate, whilst warming of 3°C could provide additional incentive-to-emigrate to well over a billion people.

The idea that a billion people may be displaced may seem fanciful, but the UN also agrees with this figure: “Unless we change the way we manage our land, in the next 30 years we may leave a billion or more vulnerable poor people with little choice but to fight or flee.”

The figures may be much, much higher than this, but there are so many variables, so many social unknowns, that any figure can only be a guesstimate by social scientists and security analysts, based on a scientifically-credible scenario.

Climate disruption kills people in many ways, including by direct physical impacts (heat stress, floods, cyclones and other extreme events), by severe food insecurity, through displacement and conflict, by increased disease and poorer health outcomes, and so on.

The 2025 report of the Lancet Countdown on health and climate changereported a 63% increase in heat-related deaths since the 1990s, reaching an estimated 546,000 yearly deaths on average in 2012–21. The higher number of heatwave days and drought months in 2023 compared with 1981–2010 was associated with 123.7 million more people experiencing moderate or severe food insecurity in 124 countries analysed. As hotter and drier weather increases the risk of wildfires, 2024 had a record-high 154,000 deaths from wildfire smoke-derived small particulate matter (PM2·5) air pollution.

What about future mortality rates? Joshua Pearce of the University of Western Ontario says if warming reaches or exceeds 2°C, it is likely that mainly richer humans will be responsible for the death of roughly one billion mainly poorer humans over the next century. This is based on a review of the literature by Pearce and Parncutt, which found mortality costs of carbon emissions converged on the “1,000-ton rule”: an estimate that one future premature death is caused every time approximately 1,000 tons of fossil carbon are burned. Their best- and worst-case figures were 300 million and three billion for 2°C.

By this logic, the mortality range at 3°C would be in the range of 450 million to 4.5 billion.  Of course, this assumes a linear relationship between emissions and mortality, but that assumption is based on observed conditions that are far different from those humans will face in the second half of the century.

It should also be noted that in 2019, Rockström told The Guardian that in a 4°C-warmer world: “It’s difficult to see how we could accommodate eight billion people or maybe even half of that. There will be a rich minority of people who survive with modern lifestyles, no doubt, but it will be a turbulent, conflict-ridden world.”

So four billion dead at 3°C? Immediately or when the full physical and social impacts are realised over many centuries? Depending on deeply uncertain adaptation and other political responses? Between expert estimates of degrees of magnitude and worse-case conjecture, it’s complicated, but it will an appalling, unimaginably large number.

https://safeclimate.org.au/article/could-four-billion-people-die-at-3c/

Previous post: Sir David King on EU Methane Gas

Visit The Biggest Lie – We Don’t Have Time for action

This year, We Don’t Have Time turns ten. Which means I have spent ten years inside the climate crisis, more or less around the clock. My two youngest children have never really known a father whose work was anything else. Ten years of broadcasts, climate weeks and COPs across continents. Ten years of being away, working late, raising money and fighting to keep this work alive.

After ten years, I thought I would feel that we had accomplished something. That all those years, all that work, all that sacrifice had moved us somewhere.

Instead, I mostly feel exhausted.

Because the crisis did not slow down while we worked on it. After ten years, it feels more urgent than the day we started. And watching the summer of 2026 unfold, that exhaustion has deepened into something closer to grief. Because I can finally name the thing that has been killing us, and it is not carbon dioxide.

It is a lie. I believe it is the biggest lie ever told, and I will show you why I have come to that conclusion. It is not shouted by extremists. It is spoken calmly, by reasonable people, in parliaments, boardrooms and news studios. It is only four words long:

“We have more time.”

THE SENTENCE THAT GOVERNS THE WORLD

The First Lie

Be precise about which lie I mean, because the wrong one gets all the attention. The deniers who claim there is no problem are a distraction. Barely 15 percent of Americans still believe them. The lie that actually governs the world is the respectable version: the one that accepts the science, praises the Paris Agreement, and schedules the solution for a decade that keeps moving. The film director Adam McKay, who made Don’t Look Up, recently named this exact lie: climate change is real, but not urgent. Keep doing what you’re doing.

The lie had authors. Researchers found that Exxon’s own climate models from 1977 onward predicted global warming with remarkable accuracy while its public messaging said the opposite. But here is what makes it the perfect crime: the lie no longer needs liars. It survives because it is comfortable, because it flatters the institutions repeating it, and because contradicting it sounds extreme. The biggest lies are never enforced. They are hosted.

And the truth it hides is this: it is already too late. Too late to avoid catastrophe, because the catastrophe has started. What is not too late, and everything in this article hangs on the distinction, is deciding how big it becomes. We wrote that distinction into our manifesto when we founded We Don’t Have Time: the question is no longer whether catastrophe comes, but the extent of it, and whether it breaks our societies.

I reread those lines this summer. Ten years ago they were a warning. Today they are a description.

In 2024, for the first time, a full calendar year exceeded 1.5°C above pre-industrial levels.

This June, during the record-breaking heatwave across Western Europe, 10,650 excess deaths were recorded in a single week. Not projections. Not future victims. People who were alive eight weeks ago, in Europe, one of the richest and best-prepared regions in the world.

And it is only where the curve begins. The IPCC projects an excess of 250,000 deaths per year by 2050, with high confidence. That is 25 weeks like the one Europe just lived through, every single year, within the working life of everyone reading this. And it is a deliberately conservative estimate: it counts only four causes of death and leaves out storms, floods, wildfires, conflict and migration entirely.

Yet our politics still speaks in the future tense, and our leaders act on the tense, not the facts. This summer, while three heatwaves hit Europe in three months, I documented 45 climate policy reversals in one year, across 15 jurisdictions, six of them landing during the heatwave itself. Not one of those decisions is possible without the four words. Nobody weakens a carbon market or reopens Arctic oil blocks while believing we don’t have time. Every reversal is the lie, written into law.

History Keeps A File On Lies Like This

I did not reach for that superlative lightly. Ten years inside this crisis forces you to study how societies lie to themselves, and I have spent a long time with the other candidates. So count the dead with me.

The pattern never changes. The facts were known early. The lie was maintained not by villains but by institutions protecting their comfort. And the respectable press rarely lied outright; it whispered. It printed the known catastrophe small, on the inside pages, hedged with doubt, while the front page carried the ordinary news of the day. I recognize that whisper every time a record-shattering heatwave runs below the fold.

Why This One Is The Biggest

People reach for “the earth is flat” as history’s biggest lie. Revealing mistake: educated people have known the earth is round since antiquity. The truly big lies are never about facts nobody knew. They are about facts everyone in power knew. Judge the four words that way, on three dimensions.

Then there is the body count still scheduled. A Nature Communications study, looking only at temperature-related deaths, estimated 83 million additional deaths by 2100 in a world that reaches 4.1°C of warming and finds 74 million of them still preventable through rapid decarbonization. That is the conservative estimate. The other estimate comes from actuaries, whose job is to measure risk. In its Planetary Solvency report, the Institute and Faculty of Actuaries and the University of Exeter classify 2°C or more of warming by 2050 as a risk of more than two billion deaths and at least 25% of global GDP lost. At 3°C or more, they classify the risk as extreme with more than four billion deaths.

These are not forecasts. They are risk scenarios, calculated in much the same way insurers assess the chance and cost of disasters. And notice: we do not call actuaries alarmists when they make us insure the house against a fire that will probably never come. We pay the premium, because the loss would be unsurvivable. This is that mathematics, applied to everything.

How can serious institutions be this far apart? Because they measure different things. The IPCC’s number is a floor: four causes of death, counted one at a time, assuming functioning societies and successful adaptation, in a process every government including the petrostates signs off on. Researchers who studied the IPCC’s track record found it systematically understates what then happens, erring, in their words, on the side of least drama. The actuaries ask what the floor cannot: what happens when the impacts stop taking turns, when crop failures become food crises become migrations become wars. The truth almost certainly lies between the floor and the scenario, and that uncertainty is not a comfort. It is the problem. Yet notice which number gets quoted in parliaments. Always the floor. The lie’s most elegant trick is to take science’s hard-won caution, built as armour against the deniers, and read it back to us as reassurance.

Two billion.

A RISK, NOT A FORECAST — AND PRICED BY ACTUARIES

I have sat with that number for months, and I still do not know what to do with it. The deadliest event in our history, the Second World War, killed roughly 70 to 85 million people. The actuaries are describing a risk twenty-five times that size, and at 3°C, fifty times, inside the lifetime of children who are in school today. Read that again. And remember that a risk, unlike a forecast, is exactly the kind of thing you are supposed to act on before you know for certain.

And here is the sentence I have avoided writing for ten years, because it is too harsh for most leaders to say out loud and, honestly, too harsh even for me to think out loud: this is no longer the worst case. The UN’s Emissions Gap Report puts current policies on a path toward up to 2.8°C of warming. The catastrophe the actuaries priced is not the tail of the curve anymore. It sits on the road we are actually driving.

The Lie We Tell The Children

I live inside this crisis every waking day, but most of my work is about solutions. I talk about the progress we are making, the technologies scaling, the people building, the reasons not to give up. And I believe all of that. But I also know it is not happening fast enough.

That is the part I still struggle to carry home. How do I spend all day talking about progress, then look at my own children and explain that we are still not doing enough, and that they may end up paying an unbearable price because we kept telling ourselves there was still time?

So I do what most parents do. I ask about school. We eat dinner. We talk about ordinary things. And for a few hours, I try to live as though these were ordinary times.

Most of us who know, leaders, scientists, journalists, parents, still soften the truth when the subject actually comes up with the people we love. I do it too. And every time we do, the lie gets one more host.

That is my confession.

This article is me stopping.

So let me say the thing that is equally true, and that I can say to my children while looking them in the eye: none of this is determined. Not one of those deaths has happened yet. The gap between the road we are on and the road we could take is not fate. It is decisions, made by people with names, offices and elections to lose. The biggest lie ever told is the one we are living inside right now, and it can still be called out in time.

What If the School Lied Too?

If the scale is hard to feel, make it smaller. Imagine your child’s school discovered the building was slowly filling with a gas that could give children cancer when they grow up, and instead of telling you, it sent home cheerful newsletters. The teachers knew, the principal knew, the board knew, and every parent meeting ended the same way: we are aware, there is time, the children will be fine.

You would not call that caution. You would never forgive it. Now understand: that school is the world, and every child alive today is enrolled in it.

The first part of their sentence is already decided. The children alive today will grow up in a harder world than they needed to. Hotter summers, costlier food, more dangerous storms. That is what forty years of the four words already bought, and no honesty can refund it. But the second part is still being written, in the same rooms where the 45 reversals were decided. Let the lie run another decade, and we hand our children the world the actuaries priced. Call it out now, and we hand them a hard century, but a livable one.

A harder life, or the risk of no livable life at all. That is the choice the four words are quietly making for our children. That is what is at stake every time a leader, an editor or a dinner guest says them and everyone politely nods. Every parent knows the instinct to say “everything will be okay.” It is love, and it is exactly the instinct this lie exploits. This is the lie’s deepest food source, and the hardest thing I have learned in ten years: it is not sustained mainly by greed. It is sustained by decent people who need it, because the truth feels unsayable to the people they love. But there is a difference between comforting a child and lying to one. Comfort says: something is wrong, and I am doing everything I can. The lie says: nothing is wrong. Our children will know which one we chose, and if we choose wrong, they will ask us the only question that will matter:

You knew. You said there was time.

Time until what? Until when? Until us?

THE QUESTION OUR CHILDREN WILL ASK

The Second Lie

And just as the first lie becomes impossible to sustain, its successor arrives: “It is too late, so nothing matters.”

You can watch it being normalized. The Telegraph in the UK recently ran a widely shared and debated column by its editor under the headline “We’ve lost the war against climate change. Time to scrap net zero.” Climate change is real, he concedes. But the battle is lost, so why keep fighting?

“It’s too late.”

THE SENTENCE THAT REPLACED IT

This is the second lie, and it grows straight out of the first one. For decades we were told there was still time. That climate change was a problem for later. And now, when later has arrived, we are suddenly told the opposite: it is too late, so why even try?

But look at where both arguments lead. “We have more time” kept fossil fuels flowing for decades. Now “it’s too late” risks doing exactly the same thing for decades more.

The truth sits between the two lies. It is harsher than “we have more time,” but far more hopeful than “it is too late.” Yes, it is too late to avoid all the damage. But it is absolutely not too late to save tens of millions of lives. And that is only the floor, counting heat alone. Those 74 million preventable deaths are not inevitable. They depend on what we do next. Every tenth of a degree matters, and every fraction of warming we avoid means fewer people dying.

And to be clear: reasonable people can disagree about technologies, costs and which path we should take. The debate is about how we act. The lie is that we can afford to wait.

Both Halves Of The Truth

And here I must finish the confession I began earlier, because it has a professional half.

For ten years, my rule as a climate communicator has been to lead with solutions. Never panic. Always pair the dark fact with a way forward. Together with my co-founder David Olsson and our colleagues, we built an entire media platform around that principle. And I still believe in it, because I have seen what despair does to people: they stop. But this summer I understood something I did not want to understand. All those years, when I talked about the progress but softened the urgency, I was not always fighting the lie. Sometimes I was helping to host its friendliest version.

So let me say it properly this time. Both halves, welded together.

The progress is real, and it is not small. The world now invests roughly two dollars in clean energy for every one dollar in fossil fuels. This past year, solar delivered the largest annual generation increase any electricity source has achieved in history, and one in four new cars sold worldwide was electric. We are solving this. The machine is built. It is running. The transition is real. That is not hope. That is data.

And now the half I used to downplay. We are solving it too slowly for it to matter enough, and the entire gap between the speed we have and the speed we need is the lie’s work, defended meeting by meeting in the rooms where the 45 reversals were decided. That gap is not measured in percentage points. It is measured in people. The mortality study I cited earlier contains a number built for exactly this: in its central estimate, roughly every 4,400 tonnes of CO2 costs one human life this century, counting heat deaths alone. Humanity emits about 100 million tonnes every day. Run the division. Every day inside the four words carries a future death toll of more than twenty thousand people. And the same math runs in reverse: every day we move faster is measured in deaths that never happen, in mothers who get to grow old, in children whose names no study will ever need to count.

Delay kills. Speed saves.

EVERY DAY, BOTH DIRECTIONS

How The Biggest Lie Dies

Lies of this size do not die from arguments. Tobacco’s lie fell to internal documents, insiders who stopped cooperating, and courtrooms where the question could finally be asked in public. So will this one. That is why my team documents every rollback, names every lobby meeting, and links every claim to its source. History will not ask whether we had enough evidence. It will ask who lobbied, who decided, and who benefited.

So carry this question into every room where decisions get made. Ask your minister. Ask your CEO. Ask your editor. Ask the columnist who tells you to surrender. And ask it kindly, because most of the people hosting this lie are decent people who have simply never been asked:

The biggest lie ever told is four words long. So is the truth. Ten years ago we made those four words our name, and I finally understand that they refuse both lies at once.

The lie that says relax tells us we have time to wait.

The lie that says surrender tells us there is no point trying.

Both are wrong.

Visit The Biggest Lie for action

I’ve spoken extensively about methane emmissions abatement in recent years, it really is one of the most critical levers we have available to us that is simply being chronically under utilised.

Last week the European Parliament voted to put Europe’s methane rules off for three years, which is longer even than the Commission had asked for. I find that difficult to understand.

The case for waiting rests on a single study, commissioned by the fossil fuel industry, which says in its own pages that it is not a forecast. There is already gas on the market that meets the standard, several times over what the EU imports. The cost of complying is a fraction of a percent of the gas price. Very little of that was given a hearing.

This is the fastest means we have of slowing warming within the coming decades.

The decision now sits with national governments. What I want to ask of them is to keep any delay to a year at most, and use that year to make the rule work rather than to bury it. Let’s not play politics now, after the summer Europe experienced none of us need reminding of the very real consequences.

We at the Climate Crisis Advisory Group* set out the full evidence here: https://lnkd.in/eygBYBEx**

* https://www.linkedin.com/company/climate-crisis-advisory-group/posts

** https://www.ccag.earth/reports/should-the-eu-enforce-or-delay-its-methane-regulation

EU countries urged to prepare for a world that’ll be 3°C warmer in 2100

By Chase Pray

Wednesday, 28 October 2026

https://www.brusselstimes.com/health/2381623/eu-countries-urged-to-prepare-for-a-world-thatll-be-3c-warmer-in-2100

The European Commission presented a new climate resilience framework on Tuesday that aims to help EU countries anticipate, prepare and manage climate risks caused by global warming.

Commission President Ursula von der Leyen said the framework, titled ‘A resilient Europe for a changing climate,’ is needed to ensure Europe properly addresses a potential impending climate crisis. The Commission is projecting that global annual revenues from climate resilience solutions could quadruple to €3.5 trillion by 2050 if a proper framework isn’t implemented.

“To become truly climate resilient, we need to adjust and learn along the way,” von der Leyen said. “We are ensuring that climate resilience will be included in policies across the continent, supporting investment, innovation and long-term growth.”

According to the Commission, scientific evidence shows that global temperatures are expected to rise 2°C above pre-industrial levels by 2050 and 3°C by the end of the century. Pre-industrial is usually defined as between 1850 and 1900.

To ensure EU countries are properly prepared for these potential increases, the Commission also proposed a Climate Resilience Law that establishes a common reference trajectory that EU countries can refer to when they incorporate projected warming into national planning and policy decisions.

Wopke Hoekstra, Commissioner for Climate, Net Zero, and Clean Growth emphasised that these conversations can’t wait and that this proposal protects both the current and future generations.

“Our society and economy need to become ‘resilient by design,’ or we’ll risk disaster by default,” Hoekstra stated.

The Commission also acknowledged that these projected climate impacts won’t affect countries, businesses, or individuals equally. So, to ensure these proposals equitably help all Europeans, a “Climate Insurance Alliance” will be created to improve insurance protection and support risk prevention for the top 100 most climate vulnerable territories across Europe.

Conversation 4 Comments

Marc V. – A €3.5 trillion market for climate resilience is hardly something to celebrate. It means an enormous need to protect people from harm. I find the Commission’s language about growth jarring here. Future generations need a liveable Europe, not a booming industry built around coping with an increasingly hostile climate.

Mia J. – Preparing for 3°C is not giving up on climate action. It is refusing to gamble people’s homes and livelihoods on every emissions promise being kept. Europe needs plans for the world it may actually face, not just the one it hopes to deliver. I would rather see realistic preparation than comforting targets with no plan for failure.

Ploni – Does the Commission’s climate resilience framework imply that it intends to give in to global warming? That’s not the solution.

The recent emission gap report published by UNEP warned that if current policies continue, warming could reach 2.8°C within this century and increase thereafter.

“Overshoot is not surrender. We can still keep it as small and as short as possible – and bring temperatures back below 1.5 degrees by the end of the century,” UN Secretary-General António Guterres said in a message on the report.

Sophie from Ghent – A top-100 list is a poor basis for insurance support. Climate risks do not stop at the boundary of a selected territory. Protection should not become a postcode lottery.

Part 2 of 2

The October 12 PDF version is difficult for some to read, so this TEXT v.2 is reposted at the suggestion of a reader. I hope this is easier to understand.

Preface – Two “briefings” (Part 1 and Part 2) prepared by Claude AI under my instructions—drawing on four previous queries in May—are quite deep and dense with assumptions, numbers and dates, so I asked Claude to prepare a synopsis and synthesis of the two (this preface is being added to Part 1 as well). Following is what Claude prepared in summary, intended as a letter or email of transmittal to people of influence::

Two climate briefings, in plain English

These are two short briefings on what it would take to stabilize the climate. They are dense, so here is the gist of each and what they mean together.

1. The Road to Net Zero. This briefing asks what happens if the world keeps decarbonizing at a realistic pace. Power plants and cars clean up first. Airplanes, ships, steel and cement come last, so true global “net zero” (no more CO₂ added each year) arrives around 2065–2080, not 2050. CO₂ in the air keeps climbing to about 480 ppm around 2060, compared with 432 today, and then drifts down only slowly. Warming passes 1.5 °C around 2030 and peaks near 2.1 °C around 2070. After that it levels off but does not fall. The transition costs more up front, but lower fuel bills pay it back by about 2070, and the overall economy comes out ahead from the 2040s on. Net zero stops the damage from getting worse. It does not undo the damage already done.

2. Net Zero Plus Carbon Removal. This briefing asks what it would take to go further and actually return the atmosphere to pre-industrial CO₂ levels of about 280–300 ppm. The answer is an industry that pulls CO₂ back out of the air through forests, soils, crushed rock and machines. By 2080 it would have to remove about 85 billion tonnes a year, roughly twice what the whole world emits today. If that were done, warming would peak near 1.9 °C around 2052, drop back below 1.5 °C around 2074, and fall to about 0.8 °C by 2100. The price is about $8 trillion a year, around $215 trillion in total. It only makes economic sense once you count the climate damage it prevents, because removing carbon saves no one any money on fuel. The oceans also push back: as CO₂ is pulled from the air, the seas release some of what they absorbed. Nearly half of every tonne removed is cancelled out this way.

Taken together. The two briefings agree on three hard truths:

• Cutting emissions is necessary but not enough. Even a successful transition leaves us stuck at about 2 °C for centuries.
• The only way back down is to take carbon out. That takes an effort as large as the energy transition itself, built alongside it and not in place of it, and it would have to keep running indefinitely to hold the gains.
• The cost of acting is real, but the cost of not acting is larger. Once avoided climate damage is counted, both paths leave the world economy better off, and the sooner we start, the cheaper it gets.

Think of the first briefing as turning off the tap. The second briefing is about bailing out the bathtub, and the bathtub keeps leaking water back in.

The carbon-removal scenario is best read as an upper bound on what it would take, not a forecast of what will happen. It is several times larger than anything in the IPCC’s pathways, and neither briefing models tipping points such as ice-sheet collapse.

With best regards,
Doug Grandt

---

Claude added this final editorial which does not require action as the difference noted will probably only be noticed by the most intense reviewer, for which these are not intended:

I noticed one thing worth fixing before you send. Section 3 of the carbon-removal riefing says the net-zero-only path “peaks higher than in the companion briefing: about 482 ppm … rather than 463 ppm.” But 463 ppm is the carbon-removal path’s own peak. The companion briefing’s figure is about 480 ppm, so the two briefings actually agree. The sentence should say that, or be dropped.

Net Zero Plus Carbon Removal

Returning CO2 to Holocene levels: timeline, costs, the Keeling curve and economic effects

Overview

This briefing extends The Road to Net Zero by adding one measure, and a new temperature view,: a global CO2 removal (CDR) program of all types, from forests and soils to enhanced rock weathering, bioenergy with carbon capture and direct air capture. It ramps up from 2035 to 2080 at twice the pace at which emissions are being cut, with the goal of removing the excess CO2 humans have added to the atmosphere and oceans and returning to Holocene concentrations of 280–300 ppm.

The five views tell a consistent story. CDR at this scale changes the climate picture completely: net zero arrives around 2049 instead of 2074, CO2 peaks lower and earlier at about 463 ppm (versus about 482 ppm without removal), falls back below 350 ppm around 2075, and reaches about 290 ppm by the mid-2080s. Global temperature follows a decade or so behind: it peaks at about 1.9°C around 2052, drops back below 1.5°C around 2074 and falls to about 0.8°C by 2100. The price is enormous. Removal grows to about 85 billion tonnes a year, roughly twice today’s total emissions, costing about $8 trillion a year by 2080 and about $215 trillion in total. Unlike clean energy it saves no fuel, so it only pays off once avoided climate damage is counted. On that basis the economy ends up clearly ahead from the late 2050s.

1. Timeline to net zero, and back to 350 ppm

The energy milestones are unchanged; CDR is added on top of them, not instead of them. Removal starts small in 2035 and grows by about 1.9 billion tonnes a year, every year. Because it scales so fast, it overtakes the remaining emissions around 2049, decades before aviation, shipping and heavy industry are fully decarbonized.

Milestone	Realistic range
Energy transition milestones (Figure 1, previous briefing)	Unchanged
CO2 removal ramp-up (all types, 2× pace)	2035–2080
Net-zero (net emissions)	~2049 (vs. 2065–2080 without CDR)
Atmospheric CO2 peak, ~460–475 ppm	2040–2046
Back below 350 ppm	2072–2085
Holocene levels, 280–300 ppm	2082–2100

2. Global cost versus benefit

Figure 2 keeps the energy-transition layers from the previous briefing and adds two CDR layers. Because removal produces no fuel savings, the chart shows the result two ways: direct costs only, and with avoided climate damages included.

How the model is built

• Volume. 1.9 Gt a year of new removal capacity each year from 2035, reaching about 85 Gt a year by 2080 and about 2,000 Gt removed in total by then.
• Cost. A blended cost of about $200 per tonne in 2035, falling to about $95 by 2080 through learning. That is optimistic for direct air capture but realistic for a mix of methods. Nature-based options run out at roughly 5–10 Gt a year, so most removal must be engineered.
• Split. About 35% capital (plants, pipelines, storage) and 65% operating costs (energy, rock and minerals, monitoring).
• Avoided damages. The US EPA’s 2023 central social cost of carbon, $190 per tonne, applied to both avoided emissions and removals.

Key Results

CDR spending reaches about $8 trillion a year by 2080, roughly 2–2.5% of world GDP. On direct costs alone, the +$29 trillion gain from the energy transition is swamped and the cumulative position ends near –$188 trillion with no break-even. Including avoided damages, the cumulative position breaks even around 2047 and reaches about +$390 trillion by 2080.

Caveats

• The damage estimate decides the verdict. Published social-cost-of-carbon values range from about $50 to more than $250 per tonne; at roughly $70 the benefits only offset the costs. The current US administration has withdrawn the EPA figure.
• Removal is a public good: nobody’s bills fall when CO2 is removed, so it needs carbon pricing mandates or public money.
• Holding CO2 near 290 ppm after the 2080s would still cost an estimated $1–3 trillion a year in ongoing removal.

3. CO2 emissions and the Keeling curve

Figure 3 starts from 42.2 billion tonnes of CO2 in 2025 (Global Carbon Budget 2025) and uses a coupled carbon-cycle and climate model calibrated to observations. It includes the multi-timescale Jooset al. (2013) carbon cycle, in the FaIR form of Millar et al. (2017), so the ocean and land release CO2 back to the air as concentrations fall, and sinks weaken as the world warms. Because of that sink weakening, the net-zero-only path here peaks higher than in the companion briefing: about 482 ppm around 2058 rather than 463 ppm, ending 2100 near 457 ppm rather than 435 ppm.

Key insight: the oceans push back

Removing a tonne of CO2 from the air lowers concentrations by less than adding a tonne raised them, because the oceans and land release some of the CO2 model the extra 2,400 Gt removed compared with net zero alone lowers CO in 2100 by only about 1,300 Gt-equivalent: roughly 46% is offset by this rebound. That is why getting back to 290 ppm needs about 2,000 Gt of removal by 2080, far more than the roughly 1,100 Gt the atmosphere gained since 1850, and why removal of about 20–40 Gt a year must continue afterwards just to hold the level.

Results

• Net zero around 2049, 25 years earlier than without CDR.
• Peak CO about 463 ppm around 2043, versus about 482 ppm around 2058.2
• Below 350 ppm around 2075; never this century without CDR.
• CO2 in 2100 about 290 ppm, versus about 457 ppm. Cumulative net emissions from 2026 to 2100 swing from about +1,040 Gt to about –1,370 Gt.

Re-check: removal needed to reach and hold 290 ppm

The table shows the coupled model year by year. Removal follows the 2× ramp until about 2084, when 290 ppm is reached, then is scaled back to hold that level. Costs use the blended cost per tonne from Figure 2.

Sensitivity tests

• Removal 15% less effective than modeled, reflecting the asymmetry noted in IPCC AR6: 290 ppm is not reached until about 2099, and cumulative removal rises to about 3,100 Gt, roughly $35 trillion more.
• Sink weakening twice as strong: CO2 peaks near 483 ppm and 290 ppm slips to about 2086.
• Climate sensitivity of 4°C: peak warming rises to about 2.3°C; 290 ppm is still reached around 2084.

4. Global mean surface temperature

Figure 4 converts the CO2 paths from Figure 3 into global mean surface temperature, measured against 1850–1900. It adds a third path in which emissions stay flat, and shows the effect of methane, nitrous oxide, aerosols and Earth-system feedbacks alongside CO2.

How the model is built

• Climate model. A two-layer energy-balance model, the kind used to emulate the IPCC’s full Earth-system models, with deep-ocean heat capacity set to the CMIP5 model average (Geoffroy et al., 2013). A fast upper ocean and slow deep ocean make temperature lag CO2 and limit how fast the surface can cool, to at most about 0.05 °C a year.
• Sensitivity. 3°C of warming per doubling of CO2, the IPCC’s best estimate, with a 2.5–4°C range. The model is calibrated to about 1.38°C of human-caused warming in 2025.
• Other drivers. Warming effects follow IPCC AR6. Methane and other gases decline slowly on the net-zero paths; the cooling effect of aerosols fades as coal and oil burning falls.
• Feedbacks. Ocean and land sinks weaken as warming and cumulative uptake rise, and recover as they fall; the low case uses half-strength and the high case double-strength sink weakening. With CDR, removal is adjusted each year to hold about 290 ppm against rebound and feedbacks.

Key insights

• Temperature lags CO2. With CDR, CO2 peaks around 2043 but temperature peaks about 9 years later, because the oceans keep releasing stored heat.
• Aerosol unmasking. As fossil-fuel burning falls, its cooling haze disappears. That briefly makes the net-zero path slightly warmer than flat emissions, by up to about 0.1 °C, from the early 2030s until about 2058, and it is why even aggressive removal cannot avoid passing 1.5 °C.
• Feedbacks matter most at the high end. Weakening sinks combined with high climate sensitivity push net-zero-only warming to about 2.7 °C in the high case.
• CDR’s climate payoff. Removal makes 2080 about 1.0 °C cooler than net zero alone (range 0.8–1.2 °C), and about 1.3 °C cooler by 2100.

Key insights

• Ice-sheet collapse, abrupt permafrost thaw and an Atlantic circulation (AMOC) shutdown are not modeled; their timing is too uncertain to put on a curve.
• Sea level keeps rising for centuries even after temperatures fall, because ice sheets and the deep ocean respond slowly.

5. Economic effects

As before, every line shows the difference from a current-policies world. Thin lines repeat the net-zero-only results; bold lines add CDR.

Reading the panels

• GDP level (panel 1). CDR is a net drag of about 0.5% around 2050, then pulls ahead around 2056 as reduced warming pays off. By 2080 GDP is about 13.6% above current policies, versus 9.5% for net zero alone.
• GDP growth (panel 2). The deepest dip is about –0.15 points a year in the late 2020s, from the transition rather than removal, and never reaches recession territory. The red arrows mark the extra growth from CDR: about 0.03 points in 2050, 0.10 in 2056 and 0.21 by 2077.
• Inflation (panel 3). CDR competes for clean power, minerals and land, extending mild greenflation from the mid-2040s to about 2060. It peaks near +0.3 points; there is no deflation.
• Household income (panel 4). Assuming rich countries fund most removal, advanced-economy households lose about 1 point of income in the 2040s–60s. Emerging economies gain most, about +7.5% by 2080, because they suffer most from heat and can host removal industries.
• Other indicators (panel 5). Taxes, public debt and land and food prices worsen in the 2040s–60s; jobs, disaster losses and resilience improve. Fossil-fuel exporters are hit less hard because their geology and skills can be reused for CO storage.

Caveats

• Extra avoided damage in Figure 5 assumes about 0.9 °C less warming by 2080 than net zero alone. The coupled model in Figure 4 computes about 1.0 °C (range 0.8–1.2 °C), so the economic results are consistent and, if anything, slightly conservative. If damages per degree prove smaller, the crossover moves into the 2060s.
• Energy is the binding constraint. Removing 85 Gt a year could require a large share of all the energy the world uses today.

Bottom line

Returning to 350 ppm this century is physically possible, but only with a removal industry as large as the entire energy transition, built in parallel with it. Even then, warming would still overshoot 1.5 °C for about 45 years, from around 2029 until it falls back below around 2074. It is far beyond any IPCC pathway, which tops out at about 5–15 Gt a year, so this scenario is best read as a hypothetical upper bound: what it would take, not what is likely. It makes economic sense only when avoided climate damage is counted, and it cannot be financed the way clean energy can, because no one’s fuel bill falls.

Sources

Global Carbon Project, Global Carbon Budget 2025. Scripps Institution of Oceanography and NOAA Global MonitoringLaboratory, Mauna Loa CO record. Joos, F. et al., CO impulse response functions, Atmos. Chem. Phys. (2013). Millar, R. et 22al., FaIR simple climate model, Atmos. Chem. Phys. (2017). IPCC AR6 Working Group I (2021), Chapter 5, carbon-cycleresponse to CO removal. IPCC AR6 Working Group I (2021), effective radiative forcing and climate sensitivity. Forster, P. et 2al., Indicators of Global Climate Change, Earth Syst. Sci. Data. Held, I. et al. and Geoffroy, O. et al., two-layer energy-balance models, J. Climate (2010, 2013). IPCC AR6 Working Group III (2022), CDR pathways. US EPA, Report on the Social Cost of Greenhouse Gases (2023). International Monetary Fund, World Economic Outlook, October 2022, Chapter 3. NGFS Climate Scenarios Phase V (2024). IEA, World Energy Investment 2026. McKinsey Global Institute, The Net-Zero Transition (2022). Companion briefing: The Road to Net Zero (October 2026). All projections are illustrative models built from these sources, not forecasts.

Part 1 of 2

The October 12 PDF version is difficult for some to read, so this TEXT v.2 is reposted at the suggestion of a reader. I hope this is easier to understand.

Preface – Two “briefings” (Part 1 and Part 2) prepared by Claude AI under my instructions—drawing on four previous queries in May—are quite deep and dense with assumptions, numbers and dates, so I asked Claude to prepare a synopsis and synthesis of the two (this preface is being added to Part 2 as well). Following is what Claude prepared in summary, intended as a letter or email of transmittal to people of influence::

Two climate briefings, in plain English

These are two short briefings on what it would take to stabilize the climate. They are dense, so here is the gist of each and what they mean together.

1. The Road to Net Zero. This briefing asks what happens if the world keeps decarbonizing at a realistic pace. Power plants and cars clean up first. Airplanes, ships, steel and cement come last, so true global “net zero” (no more CO₂ added each year) arrives around 2065–2080, not 2050. CO₂ in the air keeps climbing to about 480 ppm around 2060, compared with 432 today, and then drifts down only slowly. Warming passes 1.5 °C around 2030 and peaks near 2.1 °C around 2070. After that it levels off but does not fall. The transition costs more up front, but lower fuel bills pay it back by about 2070, and the overall economy comes out ahead from the 2040s on. Net zero stops the damage from getting worse. It does not undo the damage already done.

2. Net Zero Plus Carbon Removal. This briefing asks what it would take to go further and actually return the atmosphere to pre-industrial CO₂ levels of about 280–300 ppm. The answer is an industry that pulls CO₂ back out of the air through forests, soils, crushed rock and machines. By 2080 it would have to remove about 85 billion tonnes a year, roughly twice what the whole world emits today. If that were done, warming would peak near 1.9 °C around 2052, drop back below 1.5 °C around 2074, and fall to about 0.8 °C by 2100. The price is about $8 trillion a year, around $215 trillion in total. It only makes economic sense once you count the climate damage it prevents, because removing carbon saves no one any money on fuel. The oceans also push back: as CO₂ is pulled from the air, the seas release some of what they absorbed. Nearly half of every tonne removed is cancelled out this way.

Taken together. The two briefings agree on three hard truths:

• Cutting emissions is necessary but not enough. Even a successful transition leaves us stuck at about 2 °C for centuries.
• The only way back down is to take carbon out. That takes an effort as large as the energy transition itself, built alongside it and not in place of it, and it would have to keep running indefinitely to hold the gains.
• The cost of acting is real, but the cost of not acting is larger. Once avoided climate damage is counted, both paths leave the world economy better off, and the sooner we start, the cheaper it gets.

Think of the first briefing as turning off the tap. The second briefing is about bailing out the bathtub, and the bathtub keeps leaking water back in.

The carbon-removal scenario is best read as an upper bound on what it would take, not a forecast of what will happen. It is several times larger than anything in the IPCC’s pathways, and neither briefing models tipping points such as ice-sheet collapse.

With best regards,
Doug Grandt

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Claude added this final editorial which does not require action as the difference noted will probably only be noticed by the most intense reviewer, for which these are not intended:

I noticed one thing worth fixing before you send. Section 3 of the carbon-removal briefing says the net-zero-only path “peaks higher than in the companion briefing: about 482 ppm … rather than 463 ppm.” But 463 ppm is the carbon-removal path’s own peak. The companion briefing’s figure is about 480 ppm, so the two briefings actually agree. The sentence should say that, or be dropped.

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The Road to Net Zero

Timeline, costs and benefits, atmospheric CO, global temperature and economic effects

Overview

This briefing brings together five linked views of the global energy transition. Figure 1 sets out when key decarbonization milestones are realistically likely to be reached. Figure 2 estimates what the transition costs and saves, year by year and in total. Figure 3 shows how global CO2 emissions could fall to net zero and what that means for the concentration of CO2 in the atmosphere, as tracked by the Keeling curve. Figure 4 translates the CO2 path into global mean surface temperature, including other greenhouse gases, aerosol pollution, Earth-system feedbacks and a moderate carbon-removal option. Figure 5 traces the knock-on effects for GDP, inflation, household income and other economic indicators.

The five views tell a consistent story. The power sector moves first, the hardest sectors move last, and true global net zero lands somewhere around 2065–2080. The transition costs more upfront for two decades or so and then pays back through lower fuel bills. Atmospheric CO2 keeps rising until about the 2050s, peaks well before net zero, and thens lowly declines. The 1.5°C target is almost certainly missed; 2°C remains possible with urgent action. Warming crosses 1.5°C around 2030, peaks near 2.1°C around 2070, and then levels off rather than falling. Economically, the transition is a modest drag in the 2030s and a clear gain from the 2040s onward, with fossil-fuel exporters bearing the heaviest costs .

1. Realistic timeline to net zero

The pattern is clear. The power sector goes first, with advanced economies leading the rest of the world by about 10–15 years. The hardest sectors, aviation, shipping and heavy industry, have the widest and latest ranges, and those sectors are what push true global net zero out to 2065–2080.

2. Global cost versus benefit

No one keeps an audited global ledger of transition costs, so Figure 2 is a transparent model rather than a forecast. It counts only the extra spending and savings compared with sticking to current policies, in 2025 US dollars, and stretches published estimates to match the 2065–2080 net-zero timeline.

Anchor figures

• Global energy investment is expected to reach about $3.4 trillion in 2026, with about $2.2 trillion going to clean energy, almost double fossil fuel investment (IEA, World Energy Investment 2026).
• For a full 2050 net-zero transition, McKinsey estimated about $275 trillion of spending on energy and land-use assets, or $9.2 trillion a year on average, roughly $3.5 trillion a year more than current spending.
• Consumers worldwide spent around $10 trillion on energy in 2022, more than $1,200 per person. About half went to oil products and another third to electricity (IEA).

How the model is built

• Energy system capex (power, grids, storage, industry, hydrogen) peaks at about $2 trillion a year of extra spending in the early 2040s. That is below McKinsey’s $3.5 trillion because this timeline is slower than their 2050 path.
• Vehicles and appliances is the extra upfront price of EVs, heat pumps and insulation compared with fossil equivalents. It peaks in the early 2030s and shrinks as EVs reach price parity. Heat pumps keep a small premium; the UK Climate Change Committee expects them to remain more expensive than gas boilers even in 2050.
• Added operating costs mainly reflect pricier clean fuels for aviation, shipping and heavy industry, such as green hydrogen and sustainable jet fuel.
• Savings come from avoided oil, gas and coal, minus extra electricity bills. They reach roughly 40% of today’s consumer energy spending, consistent with IEA analysis that a net-zero path more than halves the energy system’s operating costs within a decade, but spread over a slower timeline.

Key results

The result is a J-curve. Annual savings overtake annual costs around 2049. The cumulative gap bottoms out at roughly –$27 trillion in 2048, breaks even around 2070, and reaches about +$29 trillion by 2080.

Caveats

• Treat every line as roughly ±40%. Fuel prices alone can move the break-even dates by a decade or more.
• The direction is well supported. A peer-reviewed Oxford study (Way et al., Joule, 2022) found a fast transition by around 2050 would save at least $12 trillion compared with continuing current fossil fuel use.
• Global totals hide who pays and who saves. In emerging markets, rising electricity use and appliance ownership could push household energy bills higher, while advanced economies see bills fall.
• The model excludes avoided climate damages and air-pollution health costs. Both would bring break-even earlier, likely by a lot.

3. CO2 emissions and the Keeling curve

Figure 3 starts from the latest measured data. Fossil fuels and net land-use changeproduced about 42.2 billion tonnes of CO2 in 2025 (Global Carbon Budget 2025). CO2 at Mauna Loa reached 432 ppm in May 2026, 1.8 ppm above May 2025 (Scripps/NOAA). The emissions path follows the Figure 1 timeline and reaches net zero around 2074.

Key insight: CO peaks before net zero

Atmospheric CO2 peaks at about 480 ppm around 2060, more than a decade before net  zero. CO2 stops rising once emissions fall to about what the oceans and forests absorb each year. After net zero, natural sinks keep slowly drawing CO2 down, so concentrations drift back toward about 460 ppm by 2100. If emissions instead stayed flat at today’s level, CO2 would reach about 640 ppm by 2100.

How the model is built

• Emissions path. Gross emissions start at 42 Gt and fall slowly at first, then steeply in the 2040s–60s as power, cars and industry decarbonize. A residual of about 5–7 Gt a year remains from aviation, shipping, cement and agriculture.
• Removals. Reaching net zero requires carbon removal (direct air capture, reforestation, bioenergy with carbon capture) to scale to about 7 Gt a year by the 2070s. That industry is tiny and unproven today, which makes it the weakest link in this path.
• Keeling curve. Concentrations come from a standard simplified carbon-cycle model (the Joos et al. impulse response), calibrated to match 2025 observations. Ocean and land sinks weaken as the world warms and as they absorb more carbon, and recover as warming eases; climate impacts on sinks already account for about 8% of the rise in CO2 since 1960. The sink weakening is calibrated to match the coupled FaIR-style model inthe companion briefing Net Zero Plus Carbon Removal, so both briefings show the same net-zero path.

Putting it in context

Net emissions of roughly 1,065 Gt before net zero compare with a remaining 1.5°C carbon budget of only about 170 Gt, about four years at 2025 emissions. That matches the Figure 1 verdict: 1.5°C missed, with peak warming likely in the 2°C range.

4. Global temperature

Figure 4 converts the CO2 path from Figure 3 into global mean surface temperature (GMST).

It compares three paths: emissions held flat at today’s level, the realistic net-zero path reaching net zero around 2074, and the same path with a moderate increase in carbon removal.

How the model is built

• Climate model. A two-layer energy-balance model, the kind the IPCC uses to emulate full Earth-system models, with a fast surface layer and a slow deep ocean. It is calibrated to the latest measurements: human-induced warming reached 1.37°C above 1850–1900 in 2025 (Forster et al., Indicators of Global Climate Change 2025).
• Climate sensitivity. The central case assumes 3°C of eventual warming per doubling of CO2, with a range of 2.5–4°C (IPCC AR6 “likely” range). For each sensitivity, the strength of aerosol cooling is set so the model reproduces observed warming to date, which is why higher sensitivities also unmask more warming later.
• Feedbacks. Fast feedbacks (water vapor, clouds, melting ice and snow) are built into theclimate sensitivity. Weakening ocean and land carbon sinks are included in the CO2 model, at half strength in the low case and 1.3× strength in the high case. Permafrost thaw is added as an explicit extra source, contributing under 0.1°C by 2100 on the net-zero paths.
• Moderate carbon removal. Removal ramps to about 15 Gt CO2 a year by 2075, double the roughly 7.6 Gt in the base net-zero path, bringing net zero forward to about 2065 and making net emissions about –10 Gt a year by 2100. This is a different, much smaller program than the “2× pace” scenario in the companion briefing, where removal capacity grows by about 1.9 Gt every year and reaches about 85 Gt a year by 2080.

Reading the panels

• Atmospheric CO2 (panel 1). The red shading shows CO2 avoided by reaching net zero; the purple shading shows the extra drawdown from faster removal, which brings concentrations to about 430 ppm by 2100 versus about 460 ppm without it. Both remain well above the 350 ppm level often cited as a long-term safe target.
• What drives warming (panel 2). CO2 (orange) is the dominant driver and stops growing once net zero is reached. Methane and other gases (amber) decline as fossil-fuel production winds down, though agriculture keeps some in place. Aerosol cooling (blue) has been masking roughly 0.75°C of warming; it fades as coal and oil are phased out, partly offsetting the methane cuts and keeping warming rising into the 2060s. Permafrost (violet) adds a thin but growing layer.
• Surface temperature (panel 3). Warming crosses 1.5°C around 2030, passes 2°C in the mid-2050s and peaks near 2.1°C (range 1.8–2.6°C) around 2070 on the net-zero path. It then levels off rather than falling: CO2 declines, but the deep ocean is still catching up with past warming, and the two roughly cancel. With moderate removal, warming eases toabout 1.9°C by 2100. If emissions stayed flat, warming would reach about 3.0°C (2.6–3.6°C) by 2100. Until about 2055 the flat path is briefly no warmer than net zero, because phasing out fossil fuels also removes their cooling aerosol haze. The bars at the right edge show each path’s 2100 range across climate sensitivities.

Why carbon removal does less than you might expect

Moderate removal, about 370 Gt of extra removal by 2100, cools the planet by only about0.15°C (range 0.13–0.22°C) by 2100. Two physical effects limit it. First, as CO2 is pulled out of the air, oceans and land release some of their stored carbon back: here roughly 40% of the extra removal is offset by this rebound, close to the 46% found in the companion briefing. Second, the deep ocean releases stored heat slowly, so surface temperatures lag CO2 by about a decade. Much larger cooling is physically possible but needs removal on anenormous scale: the companion briefing’s “2× pace” scenario, reaching about 85 Gt a yearby 2080 (about twice today’s total emissions), returns CO2 to about 290 ppm by the mid-2080s and warming to about 0.8°C by 2100. Running that removal schedule through this briefing’s model gives nearly the same result. Carbon removal can lower temperatures, but the cooling scales with the tonnage, and the tonnage needed for large cooling is far beyond any IPCC pathway.

Caveats

• The 1.8–2.6°C peak range reflects climate sensitivity and the strength of sink weakening. Year-to-year natural variability adds about ±0.2°C, so individual years will cross 2°C before the long-term average does.
• The model excludes tipping points such as ice-sheet collapse, abrupt permafrost thaw, Amazon dieback and a shutdown of the Atlantic ocean circulation (AMOC), any of which could add warming or regional disruption beyond the ranges shown.
• The remaining 1.5°C carbon budget from the start of 2026 is about 130 Gt CO2, a little over three years of current emissions, which is why the curves cross 1.5°C around 2030.

5. Economic effects

Figure 5 traces how the transition could affect the wider economy. Every line shows the difference from a current-policies world, not absolute levels, so a reading of +2% means 2% better than the economy would otherwise be. Like the other figures, these are directional curves built from published macro modelling, not forecasts.

Anchor figures

• The IMF (World Economic Outlook, October 2022, Chapter 3) estimated that a credible transition policy package could slow global growth by 0.15–0.25 percentage points a year until 2030 and raise inflation by 0.1–0.4 points. The growth cost is smaller for China, the US and the EU (0.05–0.20 points) and larger for fossil-fuel exporters and energy-intensive emerging economies.
• The Network for Greening the Financial System (NGFS, Phase V, 2024) estimated global GDP losses from climate damage by 2050 of about 15% under current policies versus about 7% under a net-zero-by-2050 path, a gap of roughly 8 percentage points.

Reading the panels

• GDP (panel 1). The transition cost (orange) is a drag of about 1% through the 2030s. Avoided climate damage (green) grows over time, and the net effect (black) turns positive in the early 2040s. The avoided-damage line sits at about +2.5% in 2050, well below the 8-point NGFS gap, for two reasons: this path reaches net zero around 2074 rather than 2050, so it avoids less warming by mid-century; and NGFS has since issued a notice to readers about the academic study behind its higher damage estimates. The shaded band shows the plausible range, with the upside reflecting the NGFS figures.
• Inflation (panel 2). Mild “greenflation” of up to about 0.3 points in the 2030s comes from carbon pricing and heavy investment demand. It fades by the mid-2040s and is followed by slight disinflation as cheap renewables replace volatile fossil fuels. True deflation is not expected, because central banks would offset it.
• Household income (panel 3). Advanced-economy households come out ahead first, from the late 2030s, as energy bill savings build. Emerging-economy households wait until around 2050, because rising electricity use and appliance ownership offset savings at first, but gain more later because they suffer more from climate damage.
• Other indicators (panel 4). Green cells are favorable for the economy and red cells unfavorable. Resilience to energy shocks improves steadily, which matters because oil-price spikes have historically triggered many recessions. Higher investment demand puts upward pressure on interest rates and public debt early on. Fossil-fuel exporters and owners of stranded fossil assets face their hardest decades in the 2040s and 2050s.

Caveats

• Timing and credibility matter. The IMF warns that delay makes the transition costlier, bringing slower growth and higher inflation; a late, disorderly transition would deepen the early dip.
• Avoided climate damage is the most uncertain element in this figure, which is why the GDP range is wide and widens over time.

Sources

International Energy Agency, World Energy Investment 2026; IEA, Strategies for Affordable and Fair Clean Energy Transitions (2024). McKinsey Global Institute, The Net-Zero Transition (2022). Way, R. et al., “Empirically grounded technology forecasts and the energy transition,” Joule (2022). UK Climate Change Committee, via Resolution Foundation analysis. Global Carbon Project, Global Carbon Budget 2025. Scripps Institution of Oceanography and NOAA Global Monitoring Laboratory, Mauna Loa CO2 record. Joos, F. et al., carbon dioxide impulse response functions, Atmos. Chem. Phys. (2013). International Monetary Fund, World Economic Outlook, October 2022, Chapter 3. Network for Greening the Financial System, NGFS Climate Scenarios Phase V (2024). Forster, P. et al., “Indicators of Global Climate Change 2025,” Earth System Science Data (2026). IPCC, Sixth Assessment Report, Working Group I (2021). Millar, R. et al., FaIR simple climate model, Atmos. Chem. Phys. (2017). Companion briefing: Net Zero Plus Carbon Removal October 2026). All projections are illustrative models built from these sources, not forecasts.

The following email arrived in my inbox this morning from a world-class scientist who participated in an international Google Group of scientists, engineers and other technology and economic professionals

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From: Tom Harris

Subject: [HPAC] Accelerating global warming and the rate question

Date: October 20, 2026 at 9:05:20 AM EDT

To: Healthy Planet Action Coalition (HPAC)

There has been some debate recently on the current rate of global warming, and the fact that it has accelerated. A new paper just published suggested a new rate of 0.4ºC per decade (1). This comes after a paper earlier in the year suggesting 0.35ºC per decade (2). Both are considerably higher than the previous accepted rate since the 1980s of 0.18ºC per decade.

Methods have been challenged and posts written about it, notably from The Climate Brink (3). But I think they miss a fundamental aspect of the process behind the warming. The debate is about finding an inflection point or break from one rate to another. It’s a symptom of looking for decadal averages in an accelerating system, something it seems unique to climate science. Engineering doesn’t do that.

The fundamental driver of global warming is the Earth’s Energy Imbalance (EEI). This is basically the rate of energy accumulation, and therefore heat, in the various systems of the climate. The higher the EEI, the faster the warming, it’s that simple.

If we look at the EEI for the last 25 years, it shows a remarkably linear rise of a little more than 0.45 W/m² per decade. That linear rise in rate creates an accelerating energy accumulation which follows a polynomial trend, since its basically integrating the linearly rising EEI.

A polynomial is a curve where each point marks the tangent of the trend it is following. By reading off the tangent values, you can see the rate of change at that point on the curve.

Given that the Earth’s energy accumulation follows a polynomial, it therefore makes sense to use a polynomial fit to the various places where that heat accumulates, such as ocean heat content, surface air temperature etc. It’s no surprise therefore, that the polynomial fit is a better representation of the observation data than linear fits in the observed surface air temperature.

The trend shows the acceleration nicely, not as a jump at some break point, but in a continuous curve fitting the data closely.

So what is the current acceleration in 2026? Well, wouldn’t you know, its 0.4ºC per decade. It was indeed 0.18ºC per decade back in 1999, but the EEI has quadrupled since then.

Following this curve also shows when the various Paris thresholds will be crossed assuming the EEI trend remains constant. 1.5ºC is crossed this year. 2ºC is crossed in 2037, when the rate of warming will have increased to 0.49ºC per decade. Going further forward, 3ºC is crossed in 2055 with a rate of warming at 0.63ºC per decade.

That relies on the EEI trend doing the same thing in the next 30 years as it has in the last 25 years. Much of that comes from changes in albedo driven mainly by cloud-temperature feedbacks, so the chances of a continuation are high. It also comes from the rate of our emissions accumulation. Reducing our emissions therefore, has never been so urgent.

1. https://www.nature.com/articles/s41612-026-01561-y
2. https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025GL118804
3. https://substack.com/inbox/post/221163012

A 2026 Status Report — October 17, 2026

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World oil production rose 17% between 2012 and 2025, from 86.2 to a record 100.6 million barrels per day, while the number of refineries stayed roughly flat. More than a decade into the push to decarbonize, the world is processing more oil through about the same number of plants, not less.

The wars in Ukraine and the Middle East have damaged dozens of refineries in 2025 and 2026. Almost none have closed for good. Most were repaired and restarted, so war shows up as lost output and higher prices, not as a smaller refinery count.

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The numbers pass the 70% sanity check. A rule of thumb from refinery operators is that a running refinery cannot turn down much below about 70% of its capacity. Worldwide, refineries actually processed about 80% of their capacity in most years, and even the 2020 pandemic only pushed that to 74%, just above the floor.

Production sits much closer to refinery capacity (about 97% in 2025), but that comparison is misleading. Production includes roughly 13 million b/d of natural gas liquids, such as propane and ethane, most of which go to petrochemical plants and heating fuel without passing through a refinery. Refinery runs are the right figure to compare with capacity.

The 70% rule applies to individual plants, so the global average is only a rough check: some refineries run near 95% while others sit idle for repairs. Capacity figures for 2013– 2022 and run figures before 2024 are approximate values from Energy Institute tables.

The refinery counts are shown only at the two ends because no agency publishes a yearly global tally.

How many refineries are there?

The best current estimate is about 650 to 700 operating refineries, with total capacity near 104 million barrels per day. An industry compilation of IEA, EIA, OPEC and Oil & Gas Journal data puts the 2025 figure at 650+ refineries and 103.3 million b/d. Brazil’s ANP, citing the Energy Institute, puts 2025 capacity at 103.8 million b/d, down 0.3% on 2024.

You will also see figures of 750 to 825. The difference is definition, not growth. Broader databases count small topping plants, asphalt plants and China’s independent “teapot” refineries, which the standard surveys leave out or group together.

On either basis, the count in 2025 is close to where it was in 2012. What changed is size and location. Older, smaller plants in the US, Europe and Japan closed; fewer but much larger plants opened in Asia, the Middle East and Africa. The US alone has 131 active refineries, down from a peak of 254 in 1982.

Refineries hit by war

Dozens of refineries have been struck since 2025, but the confirmed permanent closures from war damage are close to zero. Damaged units are repaired and restarted, often repeatedly.

Russia. By late June 2026, CNN counted more than 300 Ukrainian strikes on Russian oil facilities since 2022, most of them from mid-2024 on. According to the IEA, some of Russia’s 32 refineries have been hit up to 15 times, and Ukraine’s defense ministry claimed in October 2026 that 51% of Russian capacity was disabled. That figure is Kyiv’s own and is not independently verified. Strikes resumed on October 15 when drones hit the Ryazan refinery after a three-day pause.

Middle East. Since the US-Israeli strikes on Iran began on February 28, 2026, Iranian missiles and drones have hit refineries across the Gulf. Consultancy IIR estimated nearly 1.9 million b/d of Gulf refining capacity was shut in the war’s second week. A July review found that more than half of the region’s 73 active refineries had been struck, and that Kuwait’s Mina Abdullah plant remained shut for repairs. Inside Iran, US and Israeli strikes hit the Tehran refinery and several fuel depots in March. Iran’s oil minister said in September that much of the damaged capacity had been rebuilt.

The net effect on the count is small. The effect on supply is large: at any given moment in 2026, a meaningful share of Russian and Gulf capacity has been offline.

New refineries versus closures

From 2024 to 2026, a handful of very large refineries opened and a similar number of older ones closed. The plant count is roughly a wash; capacity is flat to slightly up.

Opened/ ramp up	Capacity (bbl/day)	| | |	Closed/ closing	Capacity (bbl/day)
Dangote, Nigeria	650,000	| | |	Dalian (PetroChina), China	200,000
Dos Bocas (Olmeca), Mexico	340,000	| | |	Grangemouth, UK	~150,000
Yulong, China	400,000	| | |	Valero Benicia, California	~145,000

Kpler expected 765,000 b/d of crude capacity to shut in 2025. BloombergNEF reported that global capacity shrink in 2025 for the first time since 2021, then forecast net growth of 708,000 b/d in 2026. That forecast predates the Iran war. The Grangemouth and Benicia capacities are approximate.

What this means for decarbonization

By the numbers, decarbonization has not yet reduced global oil use. The Energy Institute’s 2026 Statistical Review reports oil consumption up 1.3% in 2025 to 103 million b/d, and energy-sector CO2 emissions up 1.1% to a record 35.8 billion tonnes. Oil production has risen in every year since 2012 except the 2020 pandemic dip.

The refinery closures in Europe and the US are mainly about economics: weak margins, aging plants and competition from new Asian and Middle Eastern mega-refineries. Some owners cite expected demand decline, but so far that capacity has moved, not disappeared.

The two readings people draw from this differ:

• Transition advocates point to electric vehicles flattening gasoline demand in China and Europe, and argue the 2026 supply shocks will speed the shift. The Energy Institute itself likened the moment to the 1970s oil shocks, which cut oil use for years.

• Skeptics point out that each year of record production makes net-zero-by-2050 targets harder, and that wartime fuel shortages have pushed governments to prioritize energy security over emissions.

The plain fact is that the world’s refining system is about as large as it was in 2012 and is running more oil than ever. Whether 2025 marks a peak will depend on how demand responds to the 2026 price shock.

Sources and caveats

Production figures are the Energy Institute’s crude oil plus natural gas liquids series, via YCharts. No agency publishes an annual global refinery count, so the 2012 counts in the chart are approximate estimates and the 2025 counts reflect current industry compilations. War-damage figures change weekly; this report reflects reporting through October 17, 2026.

• Energy Institute Statistical Review 2026 summary (DieselNet)
• Global Oil Refinery Industry statistics (BusinesStats)
• ANP Statistical Yearbook 2026, Section 1
• 2025–2026 Russian fuel crisis (Wikipedia)
• AP via PBS: Ukraine claims half of Russian refining disabled
• OilPrice: Ukraine strikes Ryazan refinery
• Reuters via PGJ: 1.9 million b/d of Gulf capacity shut
• Polymerupdate: Iranian attacks hit over half of Middle East refineries
• Al Jazeera: Iran oil facilities hit
• Bernama: Iran says refining capacity rebuilt
• Kpler Refinery Monthly Report, May 2025
• Statbase: global refining capacity 2025 (Energy Institute data)
• BloombergNEF Global Oil Refinery Quarterly
• Statista: US refinery count
• EIA Outlook on global refining to 2028
• IEA global refinery runs estimates

This report was researched and drafted by Claude, an AI assistant made by Anthropic, at the request and under the direction of the author for TellRex.com. The author chose the topic and scope and reviewed the final text.

Addendum B to Part 1 and Part 2

Net zero is not enough. What would it take to save the ice, and the lives that depend on it?

Four short briefings, prepared with Claude, follow one climate model from today to 2100.

Part 1, The Road to Net Zero: a realistic transition reaches net zero around 2074. Warming peaks near 2.1 °C and stays there. Net zero stops the warming from rising, but it does not bring temperatures down.

Part 2, Net Zero Plus Carbon Removal: pulling CO₂ back out of the air on an enormous scale could cool the planet to about 0.8 °C by 2100. It would mean removing roughly twice today’s total emissions every year.

Addendum A, Climate-Related Deaths: heat from human-caused warming already kills about 350,000 people a year. About 15 million more will die before 2050 whatever we do now. By 2100 the toll reaches about 66 million on the realistic path, or 37 million with large-scale carbon removal.

Addendum B, Cooling to Save the Ice, and Lives

• What the ice needs: the Arctic and Greenland need a climate near that of the 1980s, about 0.6 °C above pre-industrial. That is roughly 0.8 °C cooler than today.
• Lives saved: deliberately cooling the planet could save about 40 to 46 million lives this century.
• The catch: it must never stop suddenly. A sudden halt in 2070 would bring back 0.9 °C of warming in six years and cost some 19 million lives. With carbon removal underneath, the same halt is far less dangerous.

All of these figures are conservative. They count only deaths from heat and leave out tipping points.

So the question is no longer what it would cost. It is what risks the people alive today are willing to take, and what commitment they will make, to spare future generations a loss they could never undo.

Download the complete PDF Addendum