Noami Oreskes and Nicholas Stern have a New York Times Opinion piece called Climate Change will cost us even more than we think. Some are very critical, others are a little more circumspect. I, on the other hand, think that Oreskes & Stern are asking an interesting question; are we properly estimating the potential impacts of climate change? I will say, though, that I’m not convinced that they’re correct that the effects of climate change are appearing faster than scientists anticipated.
When we think of tipping points, we typically mean climatic ones. For example, we could lose the West Antarctic Ice Sheet, Greenland, we could see substantial permafrost release, or we could potentially lose some ecosystems, such as the coral reefs, or the Amazon rain forest. As far as I’ve seen, we tend to regard these type of events as then leading to potentially catastrophic societal outcomes. However, it’s not obvious that this should necessarily be the case. On the one hand, losing Greenland would commit us to about 7m of sea level rise, but it might end up being slow enough to deal with. On the other hand, could there be major societal impacts even if we don’t actually cross any of these climatic tipping points?
My understanding is that this an extremely difficult problem to address. Most economic/societal models are not self-consistently modelling the evolution of the system; they’re typically assuming that society will respond to a perturbation in a way that is consistent with how its done so in the past. As the Oreskes & Stern article highights
[Economists] approach climate damages as minor perturbations around an underlying path of economic growth
Hence, this type of analysis cannot even address the question of whether or not there might be societal tipping points; it assumes, by definition, that there aren’t any. It doesn’t preclude the possibility of the impacts being large, but this would be determined entirely by the underlying change to our climate being large, not by us crossing some threshold beyond which the societal response suddenly becomes much larger. In other words, these economic models cannot consider discontinuities in how society responds to a changing climate.
Hence, as I understand it, anyone who claims that economic modelling tells us that the damages from climate change will be small is wrong; this type of modelling cannot rule out some kind of societal tipping point. It can give us some idea of how the damage might scale with warming and it can tells us something about how various policy levers might influence our future pathway. I don’t think, though, that it can rule out that society might respond in ways that were not expected, especially given that what we’re likely to experience, in the coming decades, is probably going to be unprecedented.
So, I thought that the Oreskes & Stern article was highlighting something that maybe we should be considering a bit more; could climate change cost us even more than we think? We might conclude that our estimates are reasonable, but I do think it’s a question worth asking. I also think that we should bear in mind that even if we could respond to the changes in ways that minimised the damage, there’s no guarantee that we will actually do so.