There has been quite lot of discussion recently about climate tipping points, or tipping elements. It’s mostly motivated by a recent Nature comment suggesting that Climate tipping points [are] too risky to bet against. The suggestion is that some the tipping points (West Antarctic Ice Sheet, Greenland Ice Sheet) may triggered sooner than we have anticipated. Hence, we should take this seriously and that international climate action should reflect this. One particular issue would be if there were a cascade of tipping points that, when combined, lead to some new climate state.
However, there do seem to be some who don’t entirely accept this argument, and I can see why. A lot of what is suggested about tipping points is quite speculative; it’s very difficult to quantify the actual likelihood of them being triggered. Also some (like ice sheet retreat) might still be quite slow and may not even be truly irreversible. Hence, I understand why there is some reluctance to make this a major aspect of the narrative.
However, I am starting to think that there is a problem with how we typically discuss this topic; we tend to focus more on what we think will probably happen and not enough on what might happen. Even though what will probably happen could be pretty severe, the low-probability, high-impact outcomes carry the greatest risk. So, I do think we should be talking more about the potential worst-case scenarios, but I’m not entirely sure of how best to do so.
One problem is that the outcome is conditional on what we do in future, and there are a large number of uncertainties associated with that future – what do we do in terms of future emissions, how will our emissions be taken up by the carbon sinks, how will the climate respond to the resulting atmospheric concentration, what will be the impact of this climate response, and how will we then respond to these impacts? In some sense, it’s a continually moving target.
If we fail to limit our emissions, then it becomes more likely that some of the more serious outcomes will materialise. If we start to limit our emissions, then they become less likely. If we have to consider what future pathway we might follow, what will probably happen if we follow that pathway, and also what could happen if we’re unlucky, it all gets rather convoluted. Also, if we do start to limit our emissions, do we stop talking about some of the worst case scenarios that would now be less likely than they had been before, or do we continue to highlight them in case we then start to take emission reductions less seriously?
Also, some of the tipping points/elements are so uncertain that we may have already almost triggered them, or it could still take a fairly substantial amount of additional warming. How should this influence our thinking? Clearly, if we want to avoid them we should aim to limit our emissions, but if we’re not really sure when they’d be triggered, how do we balance this with all the other factors that should influence how we go about reducing our emissions?
As you can probably tell, even though I think it is important to highlight some of the more extreme, worst-case outcomes, I’m still not sure how to do this in a way that accounts for all of the uncertainties, without it becoming so convoluted that it’s difficult to explain clearly. Similarly, how do you avoid simplifying it to the point where it is open to valid criticisms? Maybe other people have some ideas of how to do this. If so, I’d be interested to hear them.