In response to Zeke Hausfather’s and colleagues’ commentary in Nature on 4 May 2022 about the problem of “hot” climate models, I had published today in Nature a short ‘correspondence’ item. The item is reproduced below.
My point was to focus on their (rather casual) claim that “…despite some differences related to the rate of warming and aerosol forcing, the world largely looks the same at 2°C, no matter how we get there”. This is not a true statement. There are many quite radically different “two degree worlds” that can be imagined, where the differences have very little to do with the character of climate and everything to do with future trajectories of economics, politics, technology, cultural values, social cohesion, and so on. Thinking that all “two degree worlds” are basically the same is a (dangerous) form of ‘climatism’, which is the theme of my next book ‘Climate Isn’t Everything’ which will be published by Polity Press in 2023.
Zeke Hausfather and his colleagues draw attention to the problem of using ‘hot’ climate models to assess climate impacts and policy (Nature 605, 26–29; 2022). However, I disagree that the world will largely look “the same at 2?°C, no matter how we get there”. Against criteria that matter, not all future 2?°C worlds would be the same — even though the climate might be.
How we get to a global-warming temperature of 2?°C is crucial. Elements such as social cohesion, political freedoms, economic trade and inequality (B. C. O’Neill et al. Glob. Environ. Change 42, 169–180; 2017) will play as big a part as the physics of the planet.
The features of future worlds are very much a function not only of how we get there, but of how fast we do so. For example, a world that secured the 2?°C threshold in 2050 through solar geoengineering would be quite different from one that secured it in 2070 by eliminating fossil fuels. The former would still be struggling with the effects of air pollution and ocean acidification, whereas those should be of diminishing concern in the latter.
Nature 606, 250 (2022)