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...
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,...
SotA-R-7: Current Models Predict 4°C of Global Warming
(This is part 7 of the “Stages of the Anthropocene, Revisited” 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 +3.7°C. There’s no plausible peaceful path to carbon-neutrality. If there’s one key takeaway from my attempts to model carbon (CO₂-equivalent) emissions in stage 1 of the anthropocene, it’s that. Oh, and that’s it will get hot, of course. Unpleasantly hot. This the fourth in a series...
SotA-R-6: Modeling Carbon Emissions – New Results, and Thoughts on Further Models
(This is part 6 of the “Stages of the Anthropocene, Revisited” 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 +3.7°C. As mentioned in the section “limitations and alternative approaches” 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 (CO₂-equivalent) emissions in stage 1 of the anthropocene. The...
Stages of the Anthropocene
preface (2022) There are major mistakes in the predictions and calculations involved in this article. For an attempt to come up with better predictions (and thus, an update of this article), see the SotA-R series. The model results presented in the last episode thereof, suggest 3°C to 5°C of average global warming. (Original post) — Climate scientists don’t often look at the distant future and when they do, their “predictions” are so vague that they hardly count as predictions at all. Most published work on climate change focuses on the current century. There are good reasons, for this, of course...