Fair-ish and Balanced-ish
Tuesday, July 08, 2003
Castles and Henderson... Yet Again
A while ago I noted that the IPCC had replied to Ian Castles and David Henderson (the reply can be found here). I also meant to post my thoughts on their reply, but never got round to actually doing it.
Fortunately, I was reminded that I still need to do by the Australians peusdoscience editor, Alan Wood. So here goes:
Basically, Castles and Henderson's critique is now roadkill on the scientific highway. Their critique is based off ignorance and dishonesty. Rather than go into detail, it's best for any interested reader to read the reply. However, there is one important point in the reply which I'll write about in some detail.
The IPCC's last point, kind of annoys me, simply because I never thought of it. It's also leaves the Castles/Henderson critique dead in the water.
What if Ian Castles and David Henderson are right?
If Castles/Henderson are correct, then certain IPCC scenarios (especially the B1 family which gives the lowest emissions overall) have massively overestimated third world rates of development. This of course leads to a massive overestimation of future CO2 emissions.
Or does it?
A common misunderstanding among supporters of the Castles/Henderson critique is that "gdp drives emissions". In reality this statement is far to simplistic to be useful. The relationship between gdp growth and CO2 emissions is far more complicated. Economic growth growth leads to more R&D, and a more rapid replacement of old heavily polluting factories.
Or as the IPCC state:
[B]oth the resources necessary for the generation of new technological knowledge (typically R&D), as well the resources required to apply new technological knowledge, are highly dependent income levels. With no or low economic growth both R&D expenditures, as well capital turnover rates, are limited, which explains that in theory and practice technological change is ceteris paribus closely linked with income growth, or more precisely with the aggregate rate of macroeconomic productivity growth, usually represented by the growth of per capita GDP.
The result of lowering GDP growth assumptions in the developing countries in the
more optimistic scenario families A1 and B1 would therefore not change anything in
the projected emission range of the SRES scenarios. If anything, emissions would tend
to move in the direction of the low growth, slower technology scenario family A2, i.e.
be higher rather than lower as conjectured by Mr. Castles.