On “Pessimism” and “Optimism” about Climate Change; and on SRM as a “Cheap Fix”
Let’s imagine the most optimistic climate change scenario for a century from now, without going completely bonkers. To do that, let’s first split up greenhouse gas emissions (CO₂-equivalent or “CO₂e”) into non-residual and residual emissions. The latter are emissions that are difficult or impossible to (fully) eliminate due to technological or other limitations. In our scenario, non-residual emissions — that is, emissions that we can actually reduce with current technology and without disastrous socio-economic impacts — continue to grow a little bit for a while (as they do in reality), but the curve starts bending down soon (which is a...
Carbon-neutrality is dead.
So, now what?
After carbon-neutrality was declared an official goal in the 2015 Paris Agreement it became fashionable for governments and corporations to declare their intention to become carbon neutral by 2050 or soon thereafter. This was never more than an empty promise, however. The deadline was set far enough in the future to make immediate action unnecessary and few if any governments or corporations ever accepted a realistic plan to actually achieve carbon-neutrality. A decade later, they have largely given up pretense. Some have officially given up the goal; others have silently voided or discarded it. Of course, carbon-neutrality by 2050 was...
Residual Emissions
Residual emissions are carbon emissions that are difficult or impossible to (fully) eliminate due to technological or other limitations. These emissions are extremely important, because – given that we effectively cannot avoid them – they need to be compensated with various kinds of carbon removal technologies (mainly carbon capture and storage) to be able to reach net zero (or carbon-neutrality). Carbon removal is very energy intensive, however, and there are limits to how much carbon we can remove. Estimates of these limits vary, but the most optimistic ones are typically somewhere in the neighborhood of 25Gt/year, or roughly half our...
Predicting Global Warming for Dummies
Climate scientists use supercomputers and extremely complicated models to predict the future climate, but there is a shortcut that can be used to predict average global warming. The key to that shortcut is the following simple formula: $$ \Delta T_{anom.} = \frac {ECS \times ( C_{atm.} – 280 )} {280} \: – \: \psi,$$ in which \(\Delta T_{anom.}\) is the average temperature anomaly (or average global warming), \(ECS\) is “Equilibrium Climate Sensitivity”, \(C_{atm.}\) is atmospheric carbon (in ppm CO₂ equivalent), and \(\psi\) (from Greek ψῦχος, meaning “cold”) stands for various cooling effects. If you have the values of the variables...
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, 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...
Some Further Comments on Climate Sensitivity and Warming Estimates
While preparing an update of Carbon-Neutrality by 2050 (by far the most accessed page in this blog), I had another look at (equilibrium) climate sensitivity (ECS), a topic about which a wrote a few times before. ECS is the expected global temperature anomaly (i.e., the expected global average of warming) at twice the pre-industrial level of greenhouse gases (mainly CO₂) in the atmosphere (i.e., 560ppm, as “pre-industrial” is set at 280ppm). The currently most widely accepted estimate of ECS is that by Steve Sherwood and colleagues, who suggest average warming of 3.1°C (median; 66% uncertainty range: 2.6~3.9°C; 95%: 2.3~4.7°C). However,...
Rent, Profit, and Degrowth – A Postscript to “Capitalism and Climate Collapse”
In Capitalism and Climate Collapse, I argued that catastrophic climate collapse cannot be avoided under capitalism because capitalism requires economic growth, economic growth requires energy growth, energy growth requires extensive burning of fossil fuels, and extensive burning of fossil fuels causes catastrophic climate collapse. To avoid collapse, we need to shrink the economy – that is, degrowth – to a sustainable level with respect to energy requirements, and then switch to a steady state economy to stay at that level. What exactly that sustainable level is is debatable, but regardless of whether it’s closer to one third of current closer...
Capitalism and Climate Collapse
The claims that capitalism is the cause of climate change and that catastrophic climate collapse cannot be avoided under capitalism are as obvious to some people as they are nonsensical to others, but really they are neither. They are probably true, which implies that they are not nonsensical, but their (probable) truth is not obvious. They are not obvious, because these claims depend on four other claims that are themselves non-obvious: (1) capitalism requires economic growth; (2) economic growth requires energy growth; (3) energy growth requires extensive use of fossil fuels; and (4) extensive use of fossil fuels causes climate...
On Human Overpopulation
A recurring theme among a number of widely divergent political and environmental movements is that of human overpopulation. Often, the claim that there are too many humans has conspicuous racist overtones and is associated with ecofascism, but claims of overpopulation are also made by people with very different political ideas. Much of the popular overpopulation discourse appears to be quite ignorant about what “overpopulation” even means, however, and about what it might imply, so I thought it might be useful to write a few words about this. What even is “overpopulation”? “Overpopulation” is a relative term – it means that...
SotA-R-10: Combined Models 4 and 5 Suggest 62% Change of Exceeding 3°C of Average Global Warming
(This is part 10 of the “Stages of the Anthropocene, Revisited” Series (SotA-R).) The previous episode in this series explained a few problems of the last iteration of the model used to better understand feedbacks between climate change and socio-political and economic circumstances (i.e. “Model 4”). Additionally, in another recent post, I mentioned that the relation between atmospheric carbon and warming is probably better treated as linear, with time lag explaining the discrepancy between a linear equation and the current level of warming. Furthermore, that post also addressed the issue of tipping points (and other neglected feedbacks), leading to an...
The Probability of the End of Civilization in the 21st Century
Climate scientists have been calling recently for more research into warming scenarios of 3°C and above because such scenarios are dangerously neglected. According to mainstream models such levels of warming are by no means impossible or even unlikely, and would have catastrophic effects. Luke Kemp and ten colleagues write: Could anthropogenic climate change result in worldwide societal collapse or even eventual human extinction? At present, this is a dangerously underexplored topic. Yet there are ample reasons to suspect that climate change could result in a global catastrophe. The answer to the question in this quote is obviously “yes”, but that’s...
Tipping Points, Permafrost Thaw, and “Fast” Reduction
Last Thursday a new analysis of the main “tipping elements” in the Earth system was published in Science., The paper and its supplementary materials provide data on likely thresholds and effects of all the main tipping elements that have been discussed in the literature of the past two decades. Furthermore, the supplementary materials also discuss a number of other feedback effects that have been suggested as tipping elements before, but that turn out to be too gradual to be properly classified as such. These effects are at least as important, however, and tend not to be (fully) included in common...