A few days ago, I got mail from a colleague at Climate Action Network International, a communications guy, asking for a comment on the US National Academy of Sciences recent climate reports, or rather on the US emissions budget that is recommended / affirmed in these reports. It turned out to be quite an interesting request.
First up, though, these reports only strengthen the scientific case. For example, the IPCCs 2007 Forth Assessment Report says that sea levels could rise by between 0.6 and 1.9 feet by 2100, but recent studies have suggested that this is far too optimistic. The NAS reports incorporate this newer research and concludes that sea levels could rise by as much as 6.5 feet in during this century.
Second, I was a bit surprised by the way the NAS approached the problem of calculating the US emissions budget. The standard methodology in the climate world is to estimate a remaining global budget (which is hard) and then to work out the share of this budget that properly belongs to each country (which is harder). And you have to admit this approach makes sense; after all, when the US or any country takes a budget, less is left for everyone else; which is why climate, fundamentally, is a sharing problem. Anyway, I expected to find some version of this approach in the NAS reports. How else could they calculate a recommended US budget?