Stern on the costs of climate change, Part 1

John Quiggin31 Comments

The standard (expected utility) approach to assessing the cost of climate change is to
(i) derive a probability distribution for possible rates of climate change under some given projections,
(ii) attach a cost (or benefit) number to each possible outcome, expressed in utility terms,
(iii) calculate the expected utility gain (or loss)
(iv) express the calculated number as a percentage change in some income aggregate (usually GDP)

In this post, I’m going to look at step (ii). In most respects, the Stern review has adopted assumptions that favour strong action to mitigate climate change – relatively optimistic regarding the costs of stabilising CO2 levels, and relatively pessimistic regarding projections of changes in climate. But the cost calculations are conservative, probably because the previously published estimates of Mendelsohn, Nordhaus and Tol have been way too low.
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Stern on discounting and risk

John Quiggin21 Comments

One of the crucial issues in any assessment of climate change policy is how to handle discounting and risk. The Stern review (Ch 2) goes back to first principles and gets the main issues exactly right. The reason for both discounting and risk premiums, in economic analysis, is that the marginal value of a dollar of income is lower when we are rich than when we are poor. Hence, we’re prepared to pay for insurance when we are well off in order that it will pay out when we are badly off. Similarly, if we expect income to rise over time, a dollar of income now is worth more, at the margin, than a dollar in the future. The same points are relevant in considering income distribution but this isn’t covered in the parts of the report I’ve read so far.

In addition, there’s a justification for “inherent discounting”, reflecting the fact that some future event (most probably bad, but perhaps good) may mean that “all bets are off” in relation to future consumption levels. Individuals should have reasonably high inherent discount rates, since we may not be around next year, but the appopriate rate for a community is much lower, being confined to the risk of catastrophes like nuclear war.

The Stern review also has a good discussion of probabilities, including the recent literature on problems where there do not exist well-defined probabilities.

The quality of the economics here is very high, and sets a new bar for discussion of these issues.

There’s more on Stern from James Wimberley

Stern on the cost of climate stabilisation

John Quiggin49 Comments

As I said in the previous post, I plan to focus on the economics of responses to climate change from now on and the obvious place to start is the Stern report.

There’s a lot in the Stern report, and I’m going to assess it a part at a time, starting with the issue I’ve been most interested in, the cost of stabilizing atmospheric CO2 levels. I’ll focus on the case considered by Stern, and in my submission of stabilising levels at 550 parts per million, which implies a reduction in emissions of around 60 per cent, relative to business as usual, by 2050. This should be enough to avoid severe damage.
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The debate really is over now

John Quiggin115 Comments

The scientific debate over the reality of anthropogenic global warming has been over for some time, but as long as the opponents of science continued to dominate the political process, it was necessary to combat their claims.

But with the Howard government now supporting emissions trading, at least in principle, and with the overwhelming majority of the public convinced of the need for action, that necessity has now passed, at least in Australia. The main task now is to encourage the government to adopt the most efficient and effective strategies for mitigation and adaptation, in co-operation with other countries. That obviously includes signing Kyoto (with the latest change in position and with Bush a lame duck there’s no reason not to), but it could also include getting the (so-far merely decorative) AP6 process to do some work.

Of course, at least some of the denialists will keep on denying. But they’re in a hole and I’m happy to let them keep on digging. At this point, they’ll do less harm banging on about the hockey stick than they would if they accepted the reality of global warming and used what’s left of their credibility in an attempt to derail any positive response.

So from now on, I’m not going to bother refuting the absurdities of Bolt, the Lavoiser Group and other denialists. Rather than make all those who’ve enjoyed the stoush here go cold turkey, I may put up more open threads from time to time, but my future posts will be about the economics and politics of our response.

Sleaze

John Quiggin22 Comments

With a string of financial and sexual scandals affecting State Labor governments, and “corruption” being listed as one of the factors contributing to the Republicans defeat in the US, it’s worth thinking about whether issues of this kind are ephemeral events, making the headlines and then disappearing, or whether they have longer-term implications. It’s possible to point to examples going both ways. The British Conservatives acquired a reputation for sleaze in the declining years of the Thatcher-Major governments, and it took them at least a decade to recover, even up against a government that is scarcely an exemplar of probity. On the other hand, the Howard government hasn’t suffered much from a string of scandals, of which AWB is just the most recent.

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