Carbon-neutrality by 2050

(Originally published on December 15, 2020. First major revision on June 13, 2022. This is the second major version.)

A few years after carbon-neutrality became an official goal in the Paris Agreement of 2015,¹ one after the other, governments started to announce that their countries would be carbon-neutral by 2050 or a little bit later. Richer countries generally opted for 2050, while China and India, for example, aimed for 2060 and 2070, respectively. The promise of carbon-neutrality by 2050 (or 2060, or 2070) is a cheap promise, however, as the target is so far in the future that it doesn’t commit the promise-maker to take any significant immediate action. But even if the commitment is (or would be) real, one may wonder how likely it is that the target will actually be reached – if it can be reached at all – and whether it will be enough. These are two different questions, of course, and I will try to (provisionally) answer them in turn.

If you don’t want to read the whole thing, here’s a very short summary: Carbon-neutrality in 2050 is hypothetically possible, but it would probably require something like global nuclear war to wipe out most of human civilization. Due to problems like residual emissions and socio-political inertia, it is extremely unlikely – and probably even impossible – to reach carbon-neutrality by 2050 (or even by 2070) by less destructive means. Furthermore, even if we would somehow magically manage to reach that target (without exterminating most of mankind in nuclear war), this would commit us to between 2°C and 3°C of average global warming (depending on how we’d get to net zero mainly). The effects of that much warming will be devastating. It will lead to droughts, famines, natural disasters, many hundreds of millions of refugees, civil wars, and possibly collapse of the global trade system and economies dependent thereon, among other mayhem. However, it cannot be emphasized enough that this is not a reason to give up on climate action. It is never too late for action, because every tenth of a degree matters. Even if we’re destined for hell, we can still “choose” (at least in principle) how bad it is going to get.

Is carbon-neutrality by 2050 possible?

Some kinds of carbon emissions are relatively easy to bring down – others are not. It is not unlikely that in rich, industrialized countries the vast majority of passenger cars will be electric by the end of the 2030s, for example (and perhaps even sooner), but to what extent the same is achievable for road freight transport is more doubtful, and other kinds of transport will be even more problematic. Commercial flight (both cargo and passengers) will probably never be carbon-neutral, and while ocean transport could in principle return to sail, it is not likely that transport companies are actually willing to rely on wind (and certainly not on wind alone).

electricity

Even if much energy use becomes electricity-based, that electricity has to be generated somehow, and the transition to green energy appears to be much slower than needed. Power plants are typically built to provide electricity for at least 40 years, and worldwide many new fossil-fuel-burning power plants continue to be built or are scheduled to be built in the near future. If the last scheduled fossil fuel power plant is finished in 2030 (which is implausibly early), then that would commit us to carbon emission from that plant to approximately 2070, unless it would be scrapped halfway its normal operational lifespan, which is unlikely for financial reasons.

An additional problem is that it is not immediately clear whether “green” sources of energy can be sufficient to meet our (excessive!) energy needs. We’re already close to the limit for water power, for example. Wind and solar can both be significantly expanded, but both require resources that are either quite energy-intensive or relatively scarce (or both). This is a problem that I have addressed before in The Lesser Dystopia. It is possible that I was overly pessimistic when writing that article, but even a much more optimistic estimate suggests that it is unlikely that alternative sources of electric energy can ever be sufficient to provide (anywhere near) the amount of electricity we are consuming now.

Right now, approximately 95% of our energy (i.e. not just electricity!) comes from fossil fuels or other carbon fuels (such as wood). The remainder is mostly nuclear power – solar and wind are still negligible. While it may be technically possible to change this, there is no realistically possible scenario (and probably also insufficient resources) to get us from “negligible” to replacing most carbon-emitting energy production in three (or even more) decades. Carbon-neutrality, then, would require a very significant reduction in our energy consumption, but thus far that consumption is only growing. (It is probably relevant to mention here that capitalism needs economic growth and that long term economic growth is only possible by substituting energy for labor in the production process. Consequently, a significant reduction in energy consumption is not possible under capitalism.²)

residual emissions

For argument’s sake, let’s assume that a complete transition to green energy is possible by 2050, and that all transport infrastructure would be electric by then. This still leaves another major problem. Residual emissions are emissions from processes for which we have no alternative. Roughly 18% of greenhouse gas emissions result from agriculture, and about 30% is related to manufacturing industry and construction. The manufacturing of cement for the construction industry alone is responsible for approximately 7% of CO₂ emissions. Consequently, becoming carbon-neutral by 2050 also means abolishing concrete (and replacing it with a suitable alternative) by 2050. And it requires a complete overhaul of the agricultural sector. Neither of these goals would be easy to achieve. There is no good substitute for concrete on the horizon, and making agriculture carbon-neutral would require abolishing all livestock farming, rice farming, and more. Probably, we can do without meat, but a significant share of the world population depends on rice, and it is unlikely that we can decarbonize agriculture and produce enough food.

If we want to know whether and when we can reach carbon-neutrality, then, we need to know how large these residual emissions really are (and whether there is something we can do to deal with them – more about that below). This is actually not that hard to figure out. All that is needed is a spreadsheet showing carbon emissions per economic sector (etc.)³ and estimates of how much of those emissions result from processes for which we have currently no green (or greener) alternatives available (or at least not at the scale required).⁴ For example, the iron and steel industry (approximately 7.2% of carbon emissions) requires coal, and there is no feasible alternative. (But this doesn’t mean that all of those 7.2% consist of residual emissions – just the part that results from burning coal.) Such calculations show that close to 37% of all current carbon emissions are residual (i.e. cannot be reduced with currently available technology). About half of that is related to food production (if we include carbon emissions resulting from cooking food at home). Most of the rest is industrial. (Transport is negligible.)

Consequently, to reach carbon-neutrality, we either need new ways to produce our food, shut down many industries, or remove CO₂ from the atmosphere. Or some combination thereof. These are major challenges. Of course, we can build a few houses and windmills using alternative techniques, but we don’t need a few houses and windmills. The problem is scale. Things that are technically possible in unique situations or at small scales are irrelevant if they cannot scale up to feed, house, transport, and satisfy other needs of the billions of people that inhabit this planet. Realistically, we simply cannot do without concrete, steel, and other products of carbon-emitting industry. (How are we even going to make the windmills and solar cells we need without those?) And certainly we cannot do without food.

carbon capture

At this point, it is usually assumed that science fiction or magic will rescue us. Seriously… Even the reports of the Intergovernmental Panel on Climate Change (IPCC) assume that technology that doesn’t exist yet will solve the problem. Supposedly, new technologies will drive residual emissions down and make removing CO₂ from the atmosphere a real possibility. If you pay close attention to the IPCC models, you’ll see that those even depend on the assumption of very significant atmospheric carbon dioxide removal (CDR) from the atmosphere, such as direct air capture (DAC) and storage of CO₂ and other kinds of carbon capture.⁵ Without that assumption (and some other implausible assumptions, such as continuing economic growth) the IPCC scenarios fall apart.

That technological progress will lead to shrinking residual emissions is plausible. However, how fast residual emissions can shrink differs between sectors. In case of the main industrial carbon emitters (iron/steel and cement) we don’t even have a clue right now how we might be able to reduce those emissions. And in case of food production (which as mentioned, is about half of residual emissions) technological progress is unlikely to lead to fast changes. Consequently, while technological progress may indeed lead to shrinking residual emissions, this process will be very slow and will amount to a few percent points by 2050 at best. (Which means that total residual emissions would still be close to the current level, or possibly even higher, although this depends on economic growth and other factors.)

The assumption of significant carbon capture from the atmosphere followed by storage (in some form) of the captured carbon is even more dubious. It was called “magical thinking” in an editorial in Nature in 2018,⁶ and for good reasons. Because of the laws of thermodynamics, it requires more energy to remove carbon from the atmosphere than you got from the process that put that carbon in the atmosphere in the first place. So, if burning a certain amount of fossil fuels gets you X energy, then you need X+Y energy to capture and store the carbon resulting from burning those fuels.
This X+Y energy will be electricity mostly, which means that – in addition to the extra electricity needed for electric transport and electric heating – we’ll need to produce that extra electricity as well. As mentioned above, producing enough electricity for current demand by means of green technology will be virtually impossible. The idea that we could produce even more (to feed cars, heaters, air-conditioners, and atmospheric carbon removal machines) borders on insanity.⁷

nuclear fusion

Currently available green technology includes nuclear energy, by the way. If we’d have to rely on solar, wind, hydropower, and so forth alone, we’d probably not even reach 15% of current energy consumption. Of course, it’s easy to find reports online that claim that wind and solar can energize the whole planet, but if you check the details in those report, then it turns out that they assume infinite resources, infinite money, infinite labor, and zero problems and obstacles.

If we’re in science fiction territory anyway (because we currently don’t know how we’d even capture carbon from the atmosphere at anywhere near the scale required), then why not appeal to everyone’s favorite techno-solution, nuclear fusion? We’ll get all the power we need from nuclear fusion! The problem is that nuclear fusion isn’t likely to produce electricity any time soon (if ever). Advocates of nuclear fusion like to claim that fusion reactors are getting increasingly efficient, which is true, but the efficiency number they always mention is just energy output from the reaction divided by energy that is put directly in the reactor and ignores all other energy needed to run the power plant. Currently, even the most advanced power plants don’t even reach 1% efficiency – that is, energy production by the fusion reaction is less than 1% of all energy needed to run the plant (including the reactor). This efficiency (“energy return on energy invested” or EROI) needs to be greater than 10 approximately for an energy source to be economically/financially feasible,⁸ so efficiency needs to be a thousand times better than what it is now. And if we ever reach that, we’ll still have to build all the new fusion plants needed to produce the electricity we need. That’s not going to happen before 2050. That’s probably not even going to happen before 2100 (or ever).

other options?

Carbon capture and nuclear fusion are not the only science fiction scenarios that get us carbon-neutrality (albeit only in a fictional world – science fiction can never get us there in the real world). While such scenarios depend on technological science fiction, there are also socio-economic science fiction scenarios like the one I sketched in The Lesser Dystopia. In that scenario, we avoid climate-change-induced collapse by completely restructuring industry, society, politics, the economy, and so forth. The result is rather dystopian in many respects, but significantly less dystopian than collapse, of course. More importantly, while something like the measures sketched in The Lesser Dystopia would be necessary to reach carbon-neutrality (relatively peacefully), none of those measures is politically possible. Hence, scenarios like that are just as impossible in practice as technological science fiction scenarios: they assume the impossible; even if the nature of that impossibility is very different.

While it may seem that the foregoing implies that carbon-neutrality by 2050 is impossible, this is actually not the case, because there are possible scenarios that would get us there. These are not desirable scenarios, however. If it is technologically impossible to reach carbon-neutrality by reducing or compensating for residual emissions, and if it is politically impossible to reach carbon-neutrality through a complete overhaul of the ways we live, work, produce our food, and so forth, then it may seem that there is no possible pathway left. But these paths to carbon-neutrality are voluntary paths – they depend on the adoption and implementation of policies and so forth. There also are involuntary paths, however. If a global nuclear war would wipe out most of humanity,⁹ that would also completely stop most artificial carbon emissions. And there are other scenarios imaginable in which humanity would no longer be able to emit much CO₂ and other greenhouse gasses.

It is important to realize that this exhausts the options. Peaceful emission reduction or mitigation requires technological solutions that are not available (and may never be available) and/or a political and socio-economic restructuring that is so far-reaching that it never even will be considered. And reaching carbon-neutrality by other – that is, non-peaceful – means would require something like global nuclear war.

So, in conclusion then, despite (empty) promises, carbon-neutrality by 2050 will almost certainly not be reached. And if it will be reached, few (if any) of us will be around to witness it.

Is carbon-neutrality by 2050 enough?

Let’s say that we are saved by magic (or science fiction, but that’s the same, really), and we somehow manage to achieve carbon-neutrality by 2050 without killing 99% of mankind or (involuntarily) returning to medieval conditions. Then, what would the effect thereof be?

It is impossible to give an exact answer to that question for a number of reasons. First of all, virtually every aspect of climate science involved in producing such estimates works with large uncertainty margins. But perhaps even more important than that is that different trajectories towards carbon-neutrality would result in very different total greenhouse gas emissions. Rather obviously, the later we start with bringing CO₂ emissions down, the more we will emit over the three decades between now and 2050.

How much CO₂?

Currently, global annual emissions are close to 50 gigatonnes CO₂-equivalent. Let’s compare four different scenarios of bringing that down to 0 in 2050. The four different colored lines in the following figure show these four different trajectories. The blue line results in a total of 775 Gt, the red line in a total of 766 Gt, the yellow line in a total of 1131 Gt, and the green line in a total of 1028 Gt.

Since not much is happening yet in terms of emission reductions, we’re obviously not on the blue line, so that is not a realistic scenario. The red line is, more or less, the most optimistic trajectory, while the yellow and green line represents more pessimistic (?) scenarios. Obviously, even more pessimistic scenarios are possible. Given that emissions are still increasing and that we are continuing to build carbon-emitting infrastructure, I would say that the green line represents the most optimistic scenario that would be reasonably possible if carbon-neutrality by 2050 would be possible at all.

The 766 or 775 Gt of CO₂ equivalent emissions of the red and blue scenarios lead to an atmospheric CO₂-e increase of close to 50 ppm; the 1028 Gt and 1131 Gt of the green and yellow scenarios lead to roughly +65 or +70 ppm, respectively. Because there is a lot of uncertainty about natural carbon sequestering in changing atmospheric and oceanic circumstances, these numbers come with considerable uncertainty margins. We’re at approximately 422 ppm right now,¹⁰ so that will lead to between roughly 470 and 495 ppm mid century. (But remember that this ignores the fact that due to residual emissions and other factors it is effectively impossible to reach carbon-neutrality by 2050 and that actual atmospheric CO₂-e concentrations will almost certainly be higher.)

How hot will it get?

What these numbers mean in terms of warming can be inferred from the estimate of “equilibirum climate sensitivity” (ECS) by Steve Sherwood and colleagues,¹¹ although it is possible that this estimate is too optimistic.¹² ECS is the expected average global temperature increase due to a doubling of atmospheric CO₂ from pre-industrial levels of 280 ppm to 560 ppm. This is predicted to lead to 3.1°C of average global warming with a 66% likelihood range of 2.6–3.9°C and a 95% range of 2.3–4.7°C. Obviously, if we somehow (magically) manage to reach carbon-neutality by 2050, we’ll stay well below a doubling of atmospheric carbon. The blue and red scenarios would result in something like 2.1°C (66% range: 1.8–2.6°C); the yellow and green scenarios in 2.4°C (66% range: 2.0–3.0°C). If Sherwood et al.’s estimate is too optimistic indeed, and James Hansen and colleagues are right,.¹³ then these numbers are a little bit higher: 2.2°C for yellow and green, and 2.6°C for blue and red.¹⁴

A little over 2°C of average global warming may not sound like much, but the expected effects thereof are quite severe. What may be even more concerning about the effects of 2°C – more about those below – is that this level of warming puts us awfully close to the expected range of some major tipping points. In fact, in 2022 a paper was published that warned that even 1.5°C could trigger multiple tipping points.¹⁵ The data in that paper and its supplemental materials could, with some mathematical trickery, also provide an estimate of how much extra warming due to tipping elements a certain amount of direct warming produces.¹⁶ If we adjust the numbers (based on Sherwood’s ECS estimate) given in the previous paragraph accordingly, the yellow and green scenarios lead to 2.3°C (66% range: 1.8~2.9°C), and the red and blue scenarios to 2.7°C (66% range: 2.0–3.4°C).¹⁷

effects of between 2 and 3°C of warming

So, depending on the trajectory to carbon-neutrality by 2050 (and ignoring that this is actually impossible), we’d warm up the planet by between 2 and 3°C (or possibly a little bit more; less on the other hand is very improbable). Overviews of the effects of 2°C of average global warming can be found in the IPCC reports Climate Change and Land (2019) and Global Warming of 1.5°C (2018), among others, as well as in Mark Lynas’s Our Final Warning (2020), for example.¹⁸ I especially recommend Lynas’s book, which is a well-researched and well-written catalog of effects of 1 to 6°C of warming (divided into six chapters, one per degree), aimed at non-experts.

According to the first of the two IPCC reports mentioned between 2 and 2.7°C of warming, the risks associated with food security will increase from “high” to “very high”. A study published around the same predicted that 2°C of warming will result in aridification (severe drying) affecting between 18% and 24% of the global population.¹⁹ The second IPCC report mentioned made an explicit comparison between 1.5°C and 2°C of average global warming.²⁰ Here’s a very short summary: Two to three times as many species of plants, insects, and vertebrate animals will lose more than half of their geographical area. Many of these will go extinct. Approximately 13% of land area will experience ecosystem collapse (compared to 50% less at 1.5°C). Coral reefs will go virtually extinct and ocean acidification will (even) more severely threaten mollusks (shellfish, etc.), plankton, algae, and many species of fish. The loss of average annual catch for marine fisheries will be twice as high at 2°C as at 1.5°C.²¹ There will be a significantly greater reduction in crop yields for major food crops at 2 than at 1.5°C, especially in economically less developed regions. Several hundreds of millions of people more than what is expected at 1.5°C will be exposed to climate-related risks such as natural disasters, food- and water-shortage and insecurity, and poverty. Furthermore, in addition to severe and widespread problems with water availability, food security, land degradation, and so forth, 2°C or more of warming will also lead to a significant further increase of natural disasters and extreme weather such as storms (including hurricanes and typhoons), floods, deadly heatwaves, and so forth.

While the consequences of 2°C will be bad, those of 2.5°C or 3°C will be devastating. But even 2°C will be enough to cause societal collapse or civil war in some areas. This, in addition to drought, lack of food, and natural disasters will cause an explosion in the number of refugees. Most of these will stay in the same region, but many will try to reach relative safety over greater distances. The problem is that wherever these refugees will go, they are unlikely to be welcome. No part of the planet will be safe from natural disasters and other consequences of climate change, including – not unimportantly – economic consequences, such as economic decline due to faltering trade networks and destruction of economic infrastructure. Hence, wherever refugees go, they will find a society that already has too many problems of their own. More walls and border fences will likely go up for a while, but trying to keep climate refugees out is not a real option. In Six Degrees,²² Mark Lynas wrote that “In a situation of serious conflict, invaders do not take kindly to residents denying them food: if a stockpile is discovered, the householder and his family – history suggests – may be tortured and killed, both for revenge and as a lesson to others”.²³ Something similar will apply to the national or regional level: walls and armed guards cannot keep out refugees if they number in the millions, and how much trouble they will cause for the host society will largely depend on how that host society treats them. “Invaders” will not take kindly to host societies that deny them food and shelter. In 2011, Christian Parenti gave a related warning:

There is a real risk that strong states with developed economies will succumb to a politics of xenophobia, racism, police repression, surveillance, and militarism and thus transform themselves into fortress societies while the rest of the world slips into collapse. By that course, developed economies would turn into neofascist islands of relative stability in a sea of chaos. But a world in climatological collapse – marked by hunger, disease, criminality, fanaticism, and violent social breakdown – will overwhelm the armed lifeboat. Eventually, all will sink in the same morass.²⁴

2°C is probably enough to make this warning a reality. In fact, I’d say that we’re already well on our way. The answer to the question whether carbon-neutrality by 2050 is good enough, then, is clear as glass: No. If we want this planet to remain hospitable to something approaching civilization, then carbon-neutrality by 2050 is not nearly good enough.

Conclusion

So that’s the situation we’re in. Politicians make empty promises without making any effort to keep those promises. In the contrary, they keep building more fossil-fuel-burning infrastructure. Last year the United Nations released its latest emissions gap report with the title “Broken Record: Temperatures hit new highs, yet world fails to cut emissions (again)”. That, I think, says it all.

Furthermore, even if governments would make an effort, the official goal cannot be reached without magic or science fiction “solutions” that don’t exist (and may never exist). And even if somehow magically we’d manage to reach the official goal of carbon-neutrality by 2050 anyway, this would already warm up the planet so much that large parts of it become uninhabitable and the rest will have to deal with problems (such as “natural” disasters and refugees) that are so severe that economic and/or societal collapse is a serious risk in an increasing number of countries and regions.

This does not mean that we can just as well give up, however. We’re heading for catastrophe indeed, but it makes a huge difference whether that catastrophe leaves Earth inhabitable for 4 billion people or for half a billion people, for example. Every tenth of a degree matters. 2.5°C, for example, will be devastating, but 3°C (and even 2.6°C) will be even worse. We owe it to our children and our children’s children to keep as much of this planet as hospitable as possible (or as inhabitable as possible, at least). In other words, it is not too late for action. It is never too late.

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1. On the history of the idea of net zero, or carbon-neutrality, see: https://eciu.net/analysis/infographics/net-zero-history
2. See: Capitalism and Climate Collapse.
3. This data is available here: https://ourworldindata.org/emissions-by-sector
4. This data needs to be collected from a variety of sources, but with a bit of searching it can be found online.
5. Those “other kinds” capture some of the carbon at the source of its production before it can be emitted into the atmosphere.
6. Nature editorial (2018). “Negative thinking”, Nature 554 (22 February), p. 404.
7. On the exorbitant (and utterly unrealistic) energy costs of carbon dioxide removal (CDR), see also: Alexandra Deprez et al. (2024), “Sustainability limits needed for CO2 removal”, Science 383.6682: 484-6.
8. Charles Hall & Kent Klitgaard (2018). Energy and the Wealth of Nations: An Introduction to Biophysical Economics, Second Edition (Springer).
9. It wouldn’t do so directly, but the nuclear winter that would follow such a war would destroy all food production for one or more decades, and while humans can go a few days without food, a decade or more would be a bit too long.
10. See www.co2.earth for the most recent number, but notice seasonal fluctuations.
11. Steve Sherwood et al. (2020), “An assessment of Earth’s climate sensitivity using multiple lines of evidence”, Review of Geophysics 58.4: e2019RG000678.
12. See: Some Further Comments on Climate Sensitivity and Warming Estimates.
13. James Hansen et al. (2023), “Global Warming in the Pipeline”, Oxford Open Climate Change 3.1: kgad008.
14. Provided that “aerosol cooling remains constant. See: Some Further Comments on Climate Sensitivity and Warming Estimates.
15. David Armstrong McKay, Arie Staal, Jesse Abrams, Ricarda Winkelmann, Boris Sakschewski, Sina Loriani, Ingo Fetzer, Sarah Cornell1, Johan Rockström, & Timothy Lenton (2022). “Exceeding 1.5°C global warming could trigger multiple climate tipping points”, Science 377, eabn7950.
16. See: Tipping Points, Permafrost Thaw, and “Fast” Reduction.
17. In case of Hansen’s ECS estimate, adjusting for tipping elements raises the warming estimates to 2.5°C for yellow/green and 3.0°C for red/blue.
18. Mark Lynas (2020), Our Final Warning: Six Degrees of Climate Emergency (London: 4th Estate).
19. Chang-Eui Park et al. (2018). “Keeping Global Warming within 1.5ºC Constrains Emergence of Aridification”, Nature Climate Change 8: 70–74.
20. We have temporarily reached 1.5°C last year due to El Niño and will definitely pass this level some time in the next half decade or so.
21. The combination of the loss of coral reefs, plankton decline, growing dead zones, and other marine problems means that by 2050, the oceans will probably no longer be a significant source of food.
22. The previous edition of Our Final Warning. See above.
23. Mark Lynas (2007). Six Degrees: Our Future on a Hotter Planet, (Harper Collins), p. 213.
24. Christian Parenti (2011). Tropic of Chaos: Climate Change and the New Geography of Violence (Nation Books), p. 20.