Carbon-neutrality by 2050 (version of June 2022)

(Originally published on December 15, 2020. This version: June 13, 2022. The latest version can be found here.)

In the year before publication of the original version of this article (2020) several governments announced that their countries will be carbon neutral by 2050. (Since then, other countries have joined them, but often with different target years. China and India, the world’s two most populous countries, aim for 2060 and 2070, respectively, for example.) This is a cheap promise, as the target is so far in the future that it doesn’t commit them to do any significant now, but even if the commitment would be real, one may wonder how likely it is that the target will actually be reached (it 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 approximately 2°C of average global warming, which would almost certainly lead to some additional warming due to tipping points and hard-to-predict feedback effects. The effects of that level of warming will be devastating. It will lead to many hundreds of millions of refugees, civil wars, collapse of the global trade system and most economies dependent thereon, and 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 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).

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 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.)

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.)¹ 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).² 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% consists 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). 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.

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 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 direct air capture (DAC) and storage of CO₂. 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 this shrinking will be will differ a lot 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 2018,³ 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. Currently, about one quarter of carbon emissions result from electricity production. This would have to increase significantly if all transport and heating becomes electrical. As already explained above, that is probably impossible. But if we’d need additional electricity to power sufficient carbon-capturing machines to compensate residual emissions as well, we’d have to triple our current electricity production at least. It will be a struggle to produce even a quarter of our current electricity consumption by carbon-neutral means. If we’re going to need electricity for carbon-capture as well, we’re going to need 10 times more electricity than we’ll ever be able to produce with currently available “green” technology.

That “currently available green technology” includes nuclear energy, by the way. If we’d have to rely on solar, wind, hydro-power, 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. The planned, state-of-the-art ITER reactor is expected to have an efficiency of 0.1. This means that it produces one tenth of the energy that is put into the reactor. Of course, it needs to produce more energy than you put into it, so this efficiency number needs to be greater than 1, but we’re slowly getting there, and enthusiasts expect that we’ll pass the magical number 1 in a decade or so. So far so good, it seems, but there are some caveats. For a means of energy production to be feasible at scale, its energy return on energy invested (EROI) – that is, what I called “efficiency” above – needs to be greater than 10 approximately.⁴ An efficiency (EROI) of 1 isn’t nearly enough. Moreover, the 0.1 expected EROI of ITER is not the EROI of the plant as a whole, but just of part of the reactor. The expected EROI of the plant as a whole is about 0.01 and it is that number that needs to be above 10. Hence, we need a thousand-fold increase in efficiency! And we need it soon, because it takes decades to plan and built power plants and we’re going to need thousands. So, if we’re optimistic and assume that it is actually possible to reach an EROI approaching 10 and that we manage to do so in an experimental plant in a few decades from now (which, considering the speed of developments in the field is so optimistic that it is probably better characterized as insane), then fusion power may make a significant contribution to energy production near the end of the current century. (Obviously, this requires some other optimistic assumptions about this century.)

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,⁵ 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.

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 roughly 44 ppm; the 1028 Gt and 1131 Gt of the green and yellow scenarios lead to +60 or +66 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 420 ppm right now,⁶ so that will lead to between roughly 465 and 485 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.)

What these numbers mean in terms of warming can be inferred from the so-called “climate sensitivity” measure by Steve Sherwood and colleagues,⁷ discussed before in this blog. Climate sensitivity 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 67% 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-neutrality by 2050, we’ll stay well below a doubling of atmospheric carbon. The blue and red scenarios would result in something like 1.9°C; the yellow and green scenarios in 2.2°C. But notice that there are similarly wide likelihood ranges, so actual warming might turn out to be a bit more or less.

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. Although the classic study on tipping points by Timothy Lenton and colleagues suggests that it would require warming in the range of 3 to 5°C to trigger most tipping elements in the Earth system, according to Sybren Drijfhout and colleagues’ inventory of tipping points recognized by the IPCC in 2014 about two thirds of those are triggered at temperature increases below 3°C.⁸ If we pass such tipping points, this will lead to fundamental changes that cause further temperature increases, which may trigger further tipping points. One of the most worrying of these is permafrost melting because melting permafrost releases methane, but also rots away itself, putting more carbon in the atmosphere, leading to more warming. Such tipping points are not runaway effects, however – they do not lead to unlimited warming (even in case additional warming due to passing one tipping point leads to passing another). Rather, they add additional warming on top of the warming that is directly caused by us. In other words, if we warm up the planet by roughly 2°C, there is a high likelihood that “natural” processes add some further warming. It may be just a few tenths of a degree more, but the probability that it would lead to average global warming of 3°C is high enough to be worried.

In Our Final Warming, Mark Lynas has described in detail what the effects of 1 to 6°C of warming are, dedicating a chapter to each degree.⁹ The chapter titled “3 degrees”, describing the effect of +3°C can be summarized in one word: devastating. But even in the best-case scenario, reaching carbon-neutrality by 2050 would lead to roughly 2°C of warming and the effects thereof are already quite severe already.

The map below combines several predictions about drought and heat at 2°C of average global warming. (See SotA-R-2: Drought and Its Effects in the 2030s and 40s and SotA-R-3: Heat and Cyclones for details.) Yellow areas on the map can expect severe drought. Even in the light yellow areas agriculture will face serious problems. Pink areas can expect heat. Some of the heat-affected areas close to the equator are expected to be so hot that manual labor would be deadly on more than 120 (or even more than 180) days per year. In case of heat-affected areas further from the equator (such as northern India and parts of the Arabian peninsula) the main problem is deadly heatwaves. (“Deadly” in the sense that they will kill many more people than the relatively minor heatwaves we have experienced until now.) Orange and red areas on the map can expect a combination of heat and drought. Gray sea areas, finally have historically experienced major cyclones (hurricanes, typhoons, etc.). Coastal areas near those can expect a significant increase in the frequency and strength of such storms.

It’s worth emphasizing here that white areas on the map will not be problem-free. In the contrary, many of those will also experience drought and/or other “natural” disasters. Based on currently available data, those areas just aren’t among the most severely affected. Furthermore, with the growth of scientific knowledge and our abilities to run complex computer simulations, predictions like these tend to change, although usually subtly. Perhaps, newer models will suggest that parts of Europe will dry out less and China will become drier instead, for example. The overall picture hasn’t changed in a long time, however: even at 2°C of average global warming, drought, heat, extreme weather, and other “natural” disasters will cause major problems in most countries. Most likely, none will be spared.

A study published in 2018 predicted that 1.5°C of warming will result in aridification (severe drying) affecting approximately 8% of the world population, while 2°C will result in aridification that affects between 18% and 24% of the global population.¹⁰ In the same year, the IPCC published a report, Global Warming of 1.5°C, that also compares the expected effects of 1.5 and 2°C. 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. 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.

In summary, 2°C of average global warming means the collapse of agriculture in some areas (due to drought) and economic collapse in others (due to heat or other reasons); the collapse of commercial fishing (due to ocean acidification as well as warming); many more hurricanes, typhoons, uncontrollable forest fires, floods, heat waves, cold spells, and other “natural” disasters than we have already seen in the past years; the spread of tropical diseases and heat-related health problems (such as kidney damage); famines, food riots, civil wars, and wars; the collapse of parts of the global trade network and widespread economic crisis; and hundreds of millions of refugees. And every tenth of a degree more will be even worse.

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.) Furthermore, even if they 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 (and in some cases/countries/regions even likely).

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 half a billion people, for example. Again, every tenth of a degree matters, and we owe it to our children and our children’s children to keep as much of this planet as hospitable as possible. In other words, it is not too late for action. It is never too late.

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1. This data is available here: https://ourworldindata.org/emissions-by-sector
2. This data needs to be collected from a variety of sources, but with a bit of searching it can be found online.
3. Nature editorial (2018). “Negative thinking”, Nature 554 (22 February), p. 404.
4. Charles Hall & Kent Klitgaard (2018). Energy and the Wealth of Nations: An Introduction to Biophysical Economics, Second Edition (Springer).
5. 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.
6. See www.co2.earth for the most recent number, but notice seasonal fluctuations.
7. Steve Sherwood et al. (2020), “An assessment of Earth’s climate sensitivity using multiple lines of evidence”, Review of Geophysics 58.4: e2019RG000678.
8. Timothy Lenton et al. (2008), “Tipping Elements in the Earth’s Climate System”, PNAS 105.6: 1786-93. Sybren Drijfhout et al. (2015), “Catalogue of Abrupt Shifts in Intergovernmental Panel on Climate Change Climate Models”, PNAS: E5777-86. See also: Will Steffen et al. (2018), “Trajectories of the Earth System in the Anthropocene”, PNAS 115.33: 8252-9.
9. Mark Lynas (2020), Our Final Warning: Six Degrees of Climate Emergency (London: 4th Estate).
10. Chang-Eui Park et al. (2018). “Keeping Global Warming within 1.5ºC Constrains Emergence of Aridification”, Nature Climate Change 8: 70–74.