“Armstrong McKay et al. (2022) provides a summary of estimates for the effects of the 15 tipping elements identified by Lenton et al.. If we naively add up all those values we end up with an additional warming of ~1.17°C.
This is quite a lot, but does not tell the whole story, as the tipping elements differ considerably in their likely trigger temperature, whether their contribution to temperatures is positive or negative, and the timescale over which this warming would unfold. If we only add together tipping elements with an estimated trigger temperature below 3°C we end up with ~0.04°C additional warming.”
From this, would you agree it is most important to avoid a >3C world given that below that tipping points seem small?
This seems quite at odds with how this paper has been discussed in the media.
Yes, that is how I would interpret their Table S4, which seems like the main summary of their findings.
What was your impression of how the media represented their findings? It feels to me like the media often represents tipping points as happening instantaneous, while most of them are rather in the time scale of centuries.
However, you could make an argument that staying much below that is also sensible, as the tipping points are not only triggered by temperature, but also by physical processes like the dilution of salt concentrations in sea water.
Also, for writing this section I used the estimated values. If you use the minimal values for triggering the tipping points the picture becomes more grim.
How did you do those calculations? I get different results from looking at the paper Table 1 (e.g. under 3C we would expect a cooling on central estimates?)
Thank you for the article and the comments! While I agree with the finding that additional warming of tipping points seems limited in this century based on the current scientific understanding, I’d be quite hesitant to conclude that avoiding warming >3°C only is most important.
Even without strong direct, near- to medium-term impacts on global warming, tipping elements will have significant (regional) implications on ecosystems, human welfare etc. (Or, as Wang et al 2023 put it: “Overall, even considering remaining scientific uncertainties, tipping elements will influence future climate change and may involve major impacts on ecosystems, climate patterns, and the carbon cycle starting later this century. Aggressive efforts to stabilize climate change could significantly reduce such impacts.”)
In combination with the significant remaining uncertainty around tipping elements / tipping points, applying the precautionary principle and avoiding as much warming as possible appear to be good strategies, as also called for by many authors of the underlying studies/papers themselves.
Thanks. Yes, the marginal damage of missing the 3°C threshold by 0.1°C is higher than the marginal damage of missing the 1.5°C threshold by the same amount—and this gap is widening if we include tipping points.
However, benefits are cumulative—i.e. staying below e.g., 2°C reduces the risk of damages and tipping elements at that temperature threshold and those of higher temperatures. A ton of CO2 we avoid today contributes to both goals. So even in terms of relative importance, I would still disagree.
Thanks! Again it’s unclear what/who you are disagreeing with as no one is disputing that a ton permanently avoided now helps in all futures.
To clarify: The point that Florian and I were making was simply what you state that you agree with—namely that tipping points make the nonlinearity of expected climate damage worse rather than, as often argued, flattening it because nearby tipping points could easily catapult us in really high-warming futures.
This is an important point for impact-oriented philanthropists because we are, de facto, choosing between solutions with different expected performance in different futures.
From this, would you agree it is most important to avoid a >3C world given that below that tipping points seem small?
This seems quite at odds with how this paper has been discussed in the media.
Yes, that is how I would interpret their Table S4, which seems like the main summary of their findings.
What was your impression of how the media represented their findings? It feels to me like the media often represents tipping points as happening instantaneous, while most of them are rather in the time scale of centuries.
However, you could make an argument that staying much below that is also sensible, as the tipping points are not only triggered by temperature, but also by physical processes like the dilution of salt concentrations in sea water.
Also, for writing this section I used the estimated values. If you use the minimal values for triggering the tipping points the picture becomes more grim.
Just did a quick calculation. If you assume the minimal value as the trigger, you get ~0.61°C additional warming at 3°C warming.
Also, a lot more of the points are triggered at lower warming than this.
How did you do those calculations? I get different results from looking at the paper Table 1 (e.g. under 3C we would expect a cooling on central estimates?)
I used table S4, which includes a longer list of possible tipping points.
Thank you for the article and the comments! While I agree with the finding that additional warming of tipping points seems limited in this century based on the current scientific understanding, I’d be quite hesitant to conclude that avoiding warming >3°C only is most important.
Even without strong direct, near- to medium-term impacts on global warming, tipping elements will have significant (regional) implications on ecosystems, human welfare etc. (Or, as Wang et al 2023 put it: “Overall, even considering remaining scientific uncertainties, tipping elements will influence future climate change and may involve major impacts on ecosystems, climate patterns, and the carbon cycle starting later this century. Aggressive efforts to stabilize climate change could significantly reduce such impacts.”)
In combination with the significant remaining uncertainty around tipping elements / tipping points, applying the precautionary principle and avoiding as much warming as possible appear to be good strategies, as also called for by many authors of the underlying studies/papers themselves.
I don’t think anyone disagrees with it being important to reduce emissions as much as possible, the question is about relative importance.
Thanks. Yes, the marginal damage of missing the 3°C threshold by 0.1°C is higher than the marginal damage of missing the 1.5°C threshold by the same amount—and this gap is widening if we include tipping points.
However, benefits are cumulative—i.e. staying below e.g., 2°C reduces the risk of damages and tipping elements at that temperature threshold and those of higher temperatures. A ton of CO2 we avoid today contributes to both goals. So even in terms of relative importance, I would still disagree.
Thanks! Again it’s unclear what/who you are disagreeing with as no one is disputing that a ton permanently avoided now helps in all futures.
To clarify: The point that Florian and I were making was simply what you state that you agree with—namely that tipping points make the nonlinearity of expected climate damage worse rather than, as often argued, flattening it because nearby tipping points could easily catapult us in really high-warming futures.
This is an important point for impact-oriented philanthropists because we are, de facto, choosing between solutions with different expected performance in different futures.