I decided to skip over the synthesis – how can I judge that, before reading the chapters its supposed to synthesise? I’ll come back to it.
Previous: Part I.
Chapter 2 “Future carbon dioxide emissions from fossil fuels” is by Nordhaus and Yohe; and by Ausubel and Nordhaus. Eli has laid into this, but he largely based his post on Oreskes et al. (henceforth, OCS), and I no longer think thats such a good thing to do. They say: Chapter 1, written by Nordhaus, Ausubel, and Gary Yohe,… but this is, a teensy bit wrong. The chapter in question is chapter 2 (chapter 1 is the synthesis) and OCS have glossed over some subtleties. Its actually in two parts. The first is by N+Y, and is their model and their predictions. The second (p 153) is by Ausubel and N and is a review of previous work. [Update: or is it possible that in the preliminary report, it was chapter 1? And really was joint between NYA? That would be confusing, if true]
OCS manage to quote some of the chapter accurately (the first page, p 87, as it happens) widespread agreement that anthropogenic carbon dioxide emissions have been rising steadily, primarily driven by the combustion of fossil fuels…. enormous uncertainty… beyond 2000… even greater uncertainty… social and economic impacts of possible future trajectories of carbon dioxide.” So far so good, all makes perfect sense, though OCS don’t like it. OCS continue : “This uncertainty provided the basis for an argument that no meaningful action could be taken now…” but with this they seem to have gone off the rails. I can’t find that in the chapter; its not clear whether they mean the N+Y bit or the A+N bit or if they even realise there are two bits. Part 1 (N+Y) doesn’t formally have a conclusion. It does say “It should be emphasised that this conclusion about the potency of CO2 taxes is extremely tentative… Nevertheless… they suggest that a significant reduction in the concentration of CO2 will require very stringent policies, such as hefty taxes on fossil fuels. Global taxes of around $60 per ton of coal equivalent (approximately $10 per barrel of oil equivalent) reduce the concentrations of CO2 at the end of our period by only 15% from the base run… suggests that there are unlikely to be any easy ways to prevent the buildup of atmosphereic CO2.” It then suggests that adaption might be more economical, and ends by noting that whether the “imponderable side effects on society – on coastlines and agriculture, on life in high latitudes, on human health, and simply the unforeseen – will in the end prove more costly than a stringent abatement of greenhouse gases, we do not know.” Is that so terrible?
But in a sense, all of these words don’t really mean very much. What matters is their future CO2 projections, and these are shown below.
Its all probabalistic, and they say some things that would make JA squirm, but like everyone else I shall throw away the uncertainty and read their 50th percentile line, which is fully in line with AR4 (I think; I haven’t actually tried to overlay them, but it looks about OK). Their estimates are if anything on the high side: 1.6%/y to 2025, and slightly under 1% thereafter. Currently we’re at under 1%.
Of course, being economists, they only generate CO2 emissions. We want CO2 levels. They get this by M(t) = M(t-1) + AF(s)[0.471 C(t)] – sM(t-1). M is carbon mass in the atmosphere in ppm. C(t) is carbon emissions. s is the “seepage” of CO2 into the deep oceans. And AF(s) is the airbourne fraction, which they make dependent on s. Around p129 we discover that s is around 0.1% and AF about 0.47, with a range of 0.38 to 0.59. So call it 50% and we’re where we are today.
Part 2 is a review of various previous studies and I’m afraid I didn’t find it exciting enough to bother read.
The conclusion of part 2 (A+N remember; p181) is: “Careful analysis of the economy, of energy, and of CO2 emissions is vital. Such efforts are a key to better understanding of how the future atmosphere will evolve and what the likely costs and benefits of alternative CO2 control or adaption strategies will be. Considerable progress has been made over the last decade in developing more reliable and theoretically grounded models. As in other aspects of the issue of climate change, in economic and energy modelling a strong fundamental research program is a prerequisite for responding in an agile way to the concerns of today and images of the next century.” Which seems fair enough, and certainly doesn’t justify OCS’s language.
Atmoz has some discussion of chapter 2, and the “stringent” tax option.
Bits of chapter 2 are available from here. I blame brain-dead flikr for the random rotations.
So far, OCS isn’t holding up well.