I note with some glee that Marco has abandoned to me the position ‘we should do nothing about anthropogenic global warning’. His discussion over in anotherblog appears to be quibbling about the best way to do something about anthropogenic global warning. [I accidentally deleted this when trying to fix a typographical error, along with Marco's comment that he still does really think we should do nothing about global warming, he just believes there can be collateral benefits to carbon trading. So consider me gleeful instead that I have not lost my only fellow traveller!]
I admit that I have wavered somewhat over the past year, but now feel that I can assert this position with confidence. Anthropogenic global warming is a fact, but we should do nothing about it.
Item 1: Climate doesn’t kill people, Weather kills people. If the climate is likely to change to give a 25% increase in the amount of economic and human damage from weather, should we make heroic efforts to avoid this change, enormous in absolute terms? Or should we direct our efforts to protecting people and property from weather in general? Any change in climate leading to more severe storms/droughts in a particular area will be a trend laid over a pattern of variations in weather already containing many episodes of these events. If an area experiences too many droughts to be used for agriculture without subsidies from outside, it should be abandoned. If the economic productivity of a storm-affected area in good years is not enough to offest the cost of reconstructing it after bad years, it should be abandoned. Admittedly there is the possibility that Atlantic hurricanes could become regular events in the north-east and south-west Atlantic, for example, but I assert that the primary economic damage of a strong global warming event will be restricted to areas that are marginal for human use and should never have been used in the way we are using them. Nobody in their right mind ought to live in a dead-flat swamp where six-metre storm surges can occur, like the Ganges Delta or the Gulf Coast of the United States. These areas are likely to suffer recurring natural disasters and struggle to remain viable with or without global warming. Rather than do anything to slow global warming, we should abandon these areas.
Cost neutral suggestions: I recommend vegetarianism, as a way to remove the economic incentive to occupy marginal grazing lands susceptible to drought, and thalassophobia- the vast evil blue thing wants to kill us- to remove people from these dangerous places.
Item 2: Everything adapts. So a hundred years may well see a significant change in climate. In a hundred years, a farming district may cycle through three or four cash crops. In a hundred years, people can abandon one region en masse and settle another one. In a hundred years, animals and plants can also move from one place to another. Shifts in habitat are already occurring and being noted as responses to global warming. Usually these are reported with concerned tut-tutting: they need not be. Life is flexible.
Global warming cannot be uniformly bad for all environments and all species. It will be bad for some species and good for others. A naive Clammish view would say that it would favour warmer environments- which tend to support a larger number of species than cold ones. Invariably, we are likely to hear sad tales about species that are losers and find species that are winners demonised as pests. This will be irrational. Species come and species go, just like individuals. The primary difference is that unlike species, individuals can suffer or be happy: individuals are of more importance. However, I do like having lots of species around. However, preventing global warming is a very round-about and inefficient way of protecting endangered species. The evacuation of areas that are marginal for human habitation (Item 1) will present a fine opportunity to establish large reserves.
Cost neutral suggestions: I recommend open borders, to allow people to adapt optimally to new condtions, and an end to subsidies to poor uses of agricultural land, ditto.
Item 3: Lomborg is probably wrong about the main impact of global warming being on the Third World. It now appears likely that the world will not heat up uniformly, but heating will be much more marked near the poles than near the equator. A modest increase in tropical temperatures over a hundred years is unlikely to produce any impact on the Third World that could be disentangled from the pre-existing background of weather, disease, and poor governance. These are the problems that we should be tackling. Warming of the temperate/subarctic northern hemisphere, on the other hand, will have significant beneficial economic effects: reduced winter mortality, reduced energy use for heating, extended growing seasons, more available arable land, new sea routes, etc.
Item 4: We should worry about the catastrophes. Lomborg mentions in his reply to Scientific American that he did not attempt to cost certain catastrophic events, since the models suggested they had a very small likelihood of occurring. These catastrophic events play a large role in global warming consciousness-raising, however.
(a) We have no idea what degree of global warming might be necessary to kick off these events.
(b) We have no way of ensuring that, even if we emit no carbon dioxide, these events will not occur sometime in the future due to natural warming.
Therefore, instead of going to heroic efforts to aim at some target (a) which may be made redundant by (b), we should think seriously about how we can adapt to, mitigate, or reverse these possible catastrophic events.
Self-serving suggestion: We should give lots of money to scientists and engineers.
Item 5: On reflection, Item 5 is sillier than the rest, and has been omitted.
Addenda: This dodgy analysis has left out a few things we are likely to lose to global warming, but I think it will be much cheaper to save them in an ad hoc fashion. These are edifices of significant cultural value in places marginal to human habitation, and species inhabiting environments likely to vanish entirely. Polar bears presumably survived the last warm interglacial period in some refugia. We ought to locate one and ensure that a population of them remains there.