Thursday, July 10, 2008

The Hidden Cost of Global Warming

Here is some data- which was very hard to find- giving the average monthly death rate in Australia:

And just to show that 1999 was not a fluke:

If, like me, you subscribe to the germ theory of disease popularised by Louis Pasteur in the 19th century, the obvious explanation for this trend is an annual celestial event- perhaps the Earth passing through the cloud of comet debris associated with Comet 96P/Machholz, causing a rain of deadly space bacteria to Earth.

But... in the Northern Hemisphere, these same months are associated with lower mortality rates! The winter months seem to be more unhealthy if you live in a developed country in the temperate zone, despite the fact that they are less conducive for microbial growth. Go figure. Here are some data for Germany, New Zealand, and Macedonia. (Note that if you are not a developed country, the germ theory holds up just fine: a hundred years ago, our death rate was highest in summer, due to juvenile diarrhea. Actually the figures I saw on this are only for Perth c.1900 and Bangladesh today, but I am going out on a limb and generalising.)

Now, we could try mounting a complicated ad hoc rescue of the germ theory where clouds of space bacteria lurk a little above and below the plane of the ecliptic, or need to strike the atmosphere at a shallow angle to avoid burning up... but it seems that there are a whole slew of disorders, comprising the bulk of mortality, for which even small reductions in temperature give an increase in mortality. Maybe some of this mortality difference is true seasonality, but it looks like- for whatever reason- it is related to cold weather.

So who are these people who are dying? This paper from New Zealand suggests that this increase is accounted for almost entirely by deaths of people over 65. It seems logical that they will be disproportionately the ones who are sick already, and the ones who are poorer. Though I don’t have any data for this.

Thus, these excess deaths are accounted for by people, who statistically:

(1) Contribute much less to the economy than the average.

(2) Consume much more health care than the average.

Thus, cold weather clearly has an economic benefit by removing an unproductive population who are a burden on the economy. I remember that Ross Garnaut always used to write articles in the Devil Bunny City Morning Herald about the economic challenges posed by an aging population, so it is no surprise he is worried about global warming.

I believe he points out that some of this shortfall in deaths of the weak and aged might be made up for by heat-related deaths in summer, but the statistics we've looked at on seasonality of mortality in the developed world show that this is very unlikely. Unless, perhaps, we mount a crash program of not building power plants and letting electricity infrastructure decay, to increase the probability that old folks will be trapped at home without functional air-conditioning during episodes of extreme hot weather.

A serious study is required to determine if the economic cost of maintaining all these unhealthy old people will be outweighed by some of the economic benefits of global warming- such as longer dry-periods in southern Australia forcing an end to uneconomic uses of marginal land, or increased first-world mosquito-borne disease giving drug companies a greater incentive to develop treatments for these endemic third world problems.

So what is the moral of this?

It could be that a ‘cost/benefit’ analysis is never value-neutral. One person’s cost is another person’s benefit. And a short-term cost might turn out to be a long-term benefit, and vice versa. Dollars in cost/benefit analyses are not like milligrams in chemical analyses. They are more rubbery, subjective, and flamboyant entities.

It could be that it is snarky and dishonest to talk about the likely negative health effects of global warming and ignore the likely positive ones. There is this trivial point which you should verify for yourselves, not trusting me, and that you should then bring up in conversation often, that death rates in the developed world correlate overall with cold weather, not with hot weather.

Or, the moral could be that I am nothing but a contrarian sophist. Maybe I am just being silly. It guess there's a good chance that this excess seasonal mortality has nothing to do with climate, and its really all due to those weirdly gyrating clouds of space bacteria.

1 comment:

Marco said...

I really enjoyed this entry! I cannot think of anything to add though.