I haven’t written anything for a while, mainly because I’ve been busy, but partly because I haven’t really had anything to say. I think I’m finding it harder and harder to put the effort in because I don’t quite see the point. The more I get involved in this discussion, the more I get the sense that the disagreements are so fundamental that it’s pretty hard to bridge the divide.
As an example, I came across an article by Megan McArdle who argues that global warming alarmists are doing it wrong. The basic argument is that we’ve learned – from economic modelling – that it’s very difficult to make predictions for a very complex system. Therefore we shouldn’t really trust climate models.
Structural constancy, both across time and across variable conditions, is a necessary precondition for accurate forecasting. Physical systems exhibit structural constancy, but economic and social systems generally do not.
The basic point is that systems like our climate obey the fundamental laws of physics. This means two things. One is that you can eliminate any model the results of which violate any of these laws. The other is that this will always be true. Our climate won’t suddenly decide to change its mind and obey a completely different set of laws. Therefore you can essentially use the same models to study current climate change, past climate change, and future climate change. This does not mean that climate models are perfect, don’t have any problems, and that we should simply trust them. It does mean, however, that simplistic comparisons between climate models and economic models are almost certainly wrong.
This lesson from economics is essentially what the “lukewarmists” bring to discussions about climate change. They concede that all else equal, more carbon dioxide will cause the climate to warm. But, they say that warming is likely to be mild unless you use a model which assumes large positive feedback effects.
This is wrong on many levels. Firstly climate models don’t assume large positive feedbacks; the level of positive feedbacks is an emergent property of the models. It’s one of the things these models are trying to determine. Secondly, climate models are not the only reason why we think that feedbacks could be positive and large. Palaeoclimate estimates of climate sensitivity are also in line with estimates from climate models.
Finally, even the energy-balance models preferred by Lukewarmers do not rule out high climate sensitivity, and this seems to be the main problem; anyone who says “warming is likely to be mild” is essentially dismissing evidence that suggests otherwise. The discussion that we should be having is what we should do if climate sensitivity is high enough that our continued emission of CO2 could lead to substantial changes in temperature, the hydrological cycle, and extreme events. If one group has already decided that this is unlikely, and that we shouldn’t base policy on this possibility, what else is there to discuss?
So, this is why I think that the disagreements are so fundamental that any kind of meaningful discussion is almost impossible. If one group dismisses what the other regards as crucial, how can you go on from there? What’s ironic, though, is to see the same people who dismiss evidence that seems inconvenient, then complaining about others not being willing to have meaningful discussions. On that note, I shall simply end with this tweet from David Roberts:
There is something so rich about conservatives complaining that it's impossible to have a reasonable discussion about climate change.
— David Roberts (@drvox) June 1, 2016