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Usable climate science is adaptation science

Usable climate science is adaptation science

By Adam H. Sobel

Received: 30 August 2020 / Accepted: 20 April 2021/ # The Author(s), under exclusive licence to Springer Nature B.V. 2021

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Introduction: The question I ask here to what extent, and for what purposes, climate science is usable.

If we scientists wish to understand what value our work brings to the larger world... (then) thinking through our work’s direct, near-term societal consequences is a good place to start. Physical scientists are not well trained to do this kind of thinking, but the increasing urgency of the climate problem drives some of us to try. Our colleagues in the history, philosophy, and sociology of science are, on the other hand, trained to think about these kinds of problems. At the same time, they do not personally face the choice of what kind of climate science to do (or, to take it further, whether to continue doing it at all). This essay expresses one climate scientist’s attempt to put more conscious effort into thinking about how our work engages with the broader society, learning from the social scientists and humanists who focus on this problem from the outside, but not leaving the task of understanding it entirely to them.

The answer

My primary claim is that at the present historical moment, climate science is only usable to the extent that it is oriented towards climate adaptation, rather than towards climate mitigation.

For the sake of concreteness, consider climate science research that is oriented towards determining the earth’s climate sensitivity, the overall index that measures the magnitude of global mean surface warming for a given increase in greenhouse gas concentrations.4 In fact, a large fraction of all research aimed at the basic physical, chemical, and biological processes of long-term climate change fits here, in that its claim to societal value rests, directly or indirectly, on its relevance to climate sensitivity. The earth’s climate sensitivity has remained stubbornly uncertain over half a century of study. Knowledge of climate sensitivity is relevant, broadly, to climate adaptation, in that it controls the overall extent of climate change, and thus of many socio-economic impacts to which adaptation is necessary (e.g., Seneviratne et al. 2016; Arnell et al. 2019), for a given increase in greenhouse gas concentrations. Arguments have also been made, however, that it is important to reduce this uncertainty in order to provide better guidance to climate mitigation policy. Several studies, in fact, explicitly justify it as being economically valuable on this basis, as discussed further below (Cooke et al. 2014; Hope 2015; Mori and Shiogama 2018). I argue here that such arguments are wrong, because they ignore political reality, and that better knowledge of climate sensitivity is only presently usable inasmuch as it may inform climate adaptation.

To achieve even a modest probability of averting dangerous climate change — we can use either 1.5 or 2 C average global surface warming compared to pre-industrial, those being the two targets most in use — dramatic reductions are needed in greenhouse gas emissions. Here “dramatic” can be quantified by recent IPCC reports, e.g., IPCC (2018), from which we obtain Fig. 1. Just a simple visual impression of the figure, noting the sharp change in slope between the historical emissions and the future emissions required to stay under 1.5C, gives a clear indication that a sharp discontinuity between recent past and near future emissions is necessary. (A 2C threshold would change the image quantitatively but not qualitatively, in that unprecedentedly dramatic emissions reductions would still be required to reach it. So the use of the 1.5C threshold, though central to IPCC (2018)... is not consequential to the argument here.). Results such as these underlie the commonly heard statements — accepted here as true — that “time is running out.”

No emissions reductions are planned that come anywhere near those necessary to stay under either a1.5 or a 2C target. Decades of international negotiations have, by any reasonable account, been a failure. And for the four years leading up to the most recent Presidential election, national policy in the USA in particular moved in the opposite direction.

New research is very unlikely to change the situation. The results in Fig. 1 come from a particular model with a particular climate sensitivity, but the broad conclusion of interest here is robust to plausible variations in that quantity (Rogelj et al. 2018; Forster et al. 2018). A new assessment, in fact, does argue persuasively for a significant reduction in the uncertainty range for Earth’s climate sensitivity, excluding the lowest and highest values previously considered possible (Sherwood et al. 2020). This is a truly important scientific achievement. Nonetheless, it is difficult to see how it will lead to major changes in climate mitigation policy, given the historical evidence that there is little coupling between the scientific evidence and greenhouse gas emissions. Whatever the source of any expectations that there should be such coupling may have been in the past, such expectations can now be understood to be naïve about the role of politics, and the power of entrenched interests to inhibit climate action...

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