Status: this preprint was under review for the journal ESD but the revision was not accepted.
Earth System Sensitivity: a Feedback perspective
Abstract. In the field of climate-change research a lot of effort is devoted to the ‘narrowing down’ of uncertainties in the estimation of Equilibrium climate sensitivity (ECS), the global mean warming as a result of an instantaneous doubling of the CO2 concentration in the atmosphere. The present study explores possible consequences of this narrowing down of ECS for the long-term Earth system sensitivity (ESS), taking into account ‘slow’ feedbacks due to the cryosphere response (permafrost melting and ice-sheet disintegration) to a warming world. Implications for international policy making, aiming at avoiding 2 degrees Celsius of global warming, are briefly discussed.
Peter O. Passenier
Peter O. Passenier
Peter O. Passenier
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Latest update: 28 Mar 2023
In the paper Earth System Sensitivity: a Feedback perspective, Peter O. Passenier discusses emergenct constraints for equilibrium climate sensitivity (ECS) and argues that slow feedbacks (e.g. permafrost and icesheet dynamics) are not properly accounted for in previous work. The paper is short - which is nice in many respects, but I also have a concern whether it adds new information. Science papers need to explain the current state of science on the chosen topic to demonstrate that they are up to date (scholar.google search with '"emergent constraints" AND ECS' gave 239 hits, many of which were published since 2018 - most of the cited litereature herein are older than those). This manuscript doesn't do that. It may nevertheless, present some new ideas and insight, but I'm not able to say if it is or isn't. Analogies from the world of electronics, however, are interesting and probably quite novel within climate research.
Another question is whether some of the derivations and mathematics presented in the Metdods section sould be left in an appendix.
It is possible that slow feedbacks also affect the fast ones and that the dynamics and thermodynamics involve nonlinear interactions so that the total feedback no laonger is the sum of individual feedbacks. Hence, the paper assumes that the effect from various processes are additive, which I don't think has been convincingly demonstrated. The paper does, however, discuss combined earth-system feedbacks in the context of earrh system sensitivity. I think that this part needs to be explained more carefully.
I find it a bit har to see the 'red thred' in this paper, which presents a selection of 'facts' without sufficient context or explanation for why. It would be easier to follow the train of thoughts with a clearly stated hypothesis and explicit definitions. Explain why the mathematical derivations and why presenting e.g. Fig 1. It doesn't suffice doing so only in the introduction.
In conclusion, the paper present some interesting ideas, but I find it difficult to follow and think it needs to account for more of the recent progress concerning emergent constraints. Also, a more careful guidance through the ideas and concepts will make the paper easier to follow. It is always a bit more difficult to follow interdisciplinary work because some aspects often are a bit unfamiliar. Here, the paper relied on ideas from electronics in addition to maths.
Minor; 'IPPC' should be 'IPCC'.