Watts Up With That (WUWT) has a recent post called an evidence based approach to pricing CO2 emissions. It’s about a proposal by Ross Mckitrick, an economist at Guelph University.
The basic idea – presented here – seems to be that we tie a carbon tax to the rise in global surface temperatures. The basic premise – I assume – is that if global warming is happening, surface temperatures will rise and so will the carbon tax. If not, the tax will remain low.
There seems, to me at least, to be at least two – related – issues with this idea. One is that if it’s really about global warming, then tying it to surface temperatures alone means that you’re basing it on something that is only representative of a few percent of the global energy imbalance. The surface temperature evolution is also strongly influenced – on roughly decade long timescales – by natural variability, so is not always a good indicator of the underlying global warming. If the carbon tax is meant to be related to combating global warming, then basing it on the rise in Ocean Heat Content would seem more suitable. At least 90% of the excess energy goes into the oceans, so the rise in ocean heat content is a better representation of global warming, than the rise (or not) in global surface temperatures.
The other, somewhat related issue, is that even if you do think that the global surface temperature is what we should be worried about, there is a difference between the transient response and the equilibrium response. There is a lag between the addition of CO2 to the atmosphere, and the time at which we reach an equilibrium temperature. There is some evidence that the transient response (or Transient Climate Response) is maybe lower than we have previously thought, but this simply means that we have more time, not that the equilibrium value will be lower than we thought. Given that it is the equilibrium value that we should be concerned about, the carbon tax should not be based on the transient temperature (as I believe that it is), but on an estimate of the equilibrium temperature.
As an aside, it does seem as though there are a number of quite high-profile economists involved in the whole climate change debate. It does seem as though a number of them appear to be quite skeptical (to be polite) of the dangers of climate change. This whole proposal come across as a bit of a challenge. It’s as if they’re saying, “come one, you think temperatures will rise; we think they won’t. Put your money where your mouth is!”. To many, this proposal may seem reasonable. To me, it seems like something that is intended to seem reasonable despite those involved knowing – given the scientific evidence – that it is almost certainly not a particularly suitable proposal.