On āPessimismā and āOptimismā about Climate Change; and on SRM as a āCheap Fixā
Letās imagine the most optimistic climate change scenario for a century from now, without going completely bonkers. To do that, letās first split up greenhouse gas emissions (COā-equivalent or āCOāeā) 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 ā that is, emissions that we can actually reduce with current technology and without disastrous socio-economic impacts ā continue to grow a little bit for a while (as they do in reality), but the curve starts bending down soon (which is a...
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: $$ \Delta T_{anom.} = \frac {ECS \times ( C_{atm.} ā 280 )} {280} \: – \: \psi,$$ in which \(\Delta T_{anom.}\) is the average temperature anomaly (or average global warming), \(ECS\) is āEquilibrium Climate Sensitivityā, \(C_{atm.}\) is atmospheric carbon (in ppm COā equivalent), and \(\psi\) (from Greek Ļįæ¦ĻĪæĻ, meaning ācoldā) 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 doesnāt...
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 COā) in the atmosphere (i.e., 560ppm, as āpre-industrialā is set at 280ppm). The currently most widely accepted estimate of ECS is that by Steve Sherwood and colleagues, who suggest average warming of 3.1Ā°C (median; 66% uncertainty range: 2.6~3.9Ā°C; 95%: 2.3~4.7Ā°C). However,...
SotA-R-10: Combined Models 4 and 5 Suggest 62% Change of Exceeding 3Ā°C of Average Global Warming
(This is part 10 of the āStages of the Anthropocene, Revisitedā 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. āModel 4ā). 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...
Tipping Points, Permafrost Thaw, and āFastā Reduction
Last Thursday a new analysis of the main ātipping elementsā 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...
SotA-R-9: Some Comments on Model 4 (and Another Error)
[(This is part 9 of the āStages of the Anthropocene, Revisitedā Series (SotA-R).) The latest iteration of the model I have been developing in this series in an attempt to predict how much carbon we are going to emit in stage 1 of the anthropocene predicted that weāll heat up the planet by about 3.3Ā°C (67% interval: 2.3~5.0Ā°C), and that this will imply (or involve) widespread famines, civil war, refugee crises, and societal collapse. Rather than take that prediction for granted, it seemed a better idea to compare this prediction with some other predictions, and to have a closer look...
SotA-R-8: Climate/Society Feedback Model 4 Predicts 3.7Ā°C of Average Global Warming
(This is part 8 of the āStages of the Anthropocene, Revisitedā Series (SotA-R).) (This post was updated on July 28.) ā Earlier this year I found a serious error in the equations I was using to calculate warming due to carbon emissions. As explained in March, this meant that the climate/society feedback models presented in the previous three episodes in this series were all wrong, and thus that I needed to patch up the latest iteration of those models. The result of that āpatching upā is model 4, which is mostly identical to model 3. The only differences are the...
SotA-R-7: Current Models Predict 4Ā°C of Global Warming
(This is part 7 of the āStages of the Anthropocene, Revisitedā Series (SotA-R).) Important Note (March 3, 2022) Due to a fundamental flaw in models 1, 2, and 3 in this series, the predictions for average global warming in this article are unreliable. Update (May 21, 2022) Model 4 fixes this problem and predicts +3.7Ā°C. Thereās no plausible peaceful path to carbon-neutrality. If thereās one key takeaway from my attempts to model carbon (COā-equivalent) emissions in stage 1 of the anthropocene, itās that. Oh, and thatās it will get hot, of course. Unpleasantly hot. This the fourth in a series...
SotA-R-6: Modeling Carbon Emissions ā New Results, and Thoughts on Further Models
(This is part 6 of the āStages of the Anthropocene, Revisitedā Series (SotA-R).) Important Note (March 3, 2022) Due to a fundamental flaw in models 1, 2, and 3 in this series, the predictions for average global warming in this article are unreliable. Update (May 21, 2022) Model 4 fixes this problem and predicts +3.7Ā°C. As mentioned in the section ālimitations and alternative approachesā of the previous episode in this series, there were a couple of things I wanted to change in the model (i.e. spreadsheet) used to simulate global carbon (COā-equivalent) emissions in stage 1 of the anthropocene. The...
SotA-R-5: Modeling Carbon Emissions in Stage 1 of the Anthropocene ā a First Attempt
(This is part 5 of the āStages of the Anthropocene, Revisitedā Series (SotA-R).) Important Note (March 3, 2022) Due to a fundamental flaw in models 1, 2, and 3 in this series, the predictions for average global warming in this article are unreliable. Update (May 21, 2022) Model 4 fixes this problem and predicts +3.7Ā°C. The aim of this series is a better prediction of the long-term prospects for human civilization (in the context of climate change) than the rather sketchy predictions made in Stages of the Anthropocene three years ago. The previous episodes in this series discussed some relavant...
SotA-R-4: Preliminary Notes on Modeling Carbon Emission Scenarios in Stage 1 of the Anthropocene
(This is part 4 of the āStages of the Anthropocene, Revisitedā Series (SotA-R).) The purpose of this series is an update of the mid- and long-term prediction of aspects of the global climate relevant for the prospects of continuing human civilization in Stages of the Anthropocene. The idea is to develop a model that can be relatively easily expanded, fine-tuned, and corrected when new or better information becomes available. The present episode in the series consists of a number of notes of a relatively technical nature on how to build this model. COā emissions and economic growth The level of...