James raises two important issues. My point that we are adapted to current climate is, in my view, the more straightforward (if we aren't adapted to our current conditions then what conditions did we have in mind and why?). So I'll start by elaborating on that claim then move to the second and more challenging issue of how much economic damage is done by emitting a unit of greenhouse gases.
Sea level and our current development patterns along the coast offer one good example of how we're adapted to current conditions. We've built (adapted) based on where the sea is now not where sea level is headed. It may not inherently make much difference if sea level is higher or lower as we would have taken that in to account as we originally developed but now it matters a great deal because of these past choices. Snowpack in the western United States offers another example. We're adapted (imperfectly, of course) to the provision of fresh water from that snowpack, which is and will continue to change as precipitation patterns and the timing of spring melt change. Unlike James, I also liked Andrew Dessler's hypothetical example of the sawmill being located where a river (and a forest) is. If the location of the river or the forest change (both of which are at least partly determined by climate) we'd have to abandon that mill and build a new one or make do with one less well adapted to the new conditions. In my view, this issue of adaptation to existing climate gets much more challenging for us when we think more broadly about the physical and natural systems that we depend on and which are also heavily adapted to current conditions. Eric's example about natural pollinators, touched on this nicely. His example is illustrative of a larger group of goods and services provided to human society that most of us (including many economists, as I'll discuss in a minute) take for granted and ignore when thinking about the economic costs of climate change. Forests, for example, help reduce flooding and droughts by taking up and slowly releasing water over time. Critically, biological systems also help purify water and the air, detoxify and decompose of wastes, maintain and promote soil fertility, help control pests and diseases, help stabilize climate (locally, regionally, and globally), and help reduce the impact of natural disasters. This all gets provided free of charge and generally stays outside of market transactions (these are non-market goods and services). Human societies have demonstrated a remarkable ability to adapt to different climates (though so far maybe not much capacity to adapt to climate changes). This is much less true of other species and other biological systems, which often have fairly narrow climate requirements and which face relatively rapid rates of climate change. As a result, the changes in climate that we're already seeing are having impacts on biological systems. These impacts pose risks to the goods and services those systems provide. Again, it isn't that the new climate is necessarily better or worse, inherently, the problem is that these systems are adapted to current conditions. I should add that it is possible for society to be adapted to current climate and still have net economic benefits from climate change because humans have the capacity to adapt as those changes occur and thereby minimize economic harm and maximize economic benefits. I also agree with Michael's point that some locations may see climate improvements. My point is really that being adapted to current climate loads the dice toward economic damages. So getting net economic benefits from climate change is a low probability outcome, in my view, as I'll explain further. This brings us to the second question, which is much more difficult, in my view. How much economic damage is done by emitting a unit of greenhouse gases? I think it fair to say that we don't know, and probably can't know, with a great deal of certainty ahead of time. Existing economic estimates also vary widely. It's certainly true that some economic studies suggest net benefits are possible (for small changes in climate agriculture and shipping may both tend to improve, for example). But that isn't a widespread view or a consistent finding. Indeed, my sense is that net economic benefits only come about in economic analysis that is far too limited in scope to offer much insight in the real world. I believe that five factors are particularly important in determining the estimates of climate damages from recently emitted greenhouse gases (NB, this is not an area of expertise for me): how climate change is considered (whether mean changes in temperature only or a broader examination of characteristics and extremes) our adaptive capacity, discount rate (how much we value the future relative to the present), the extent that non-market goods and services get included (e.g., floods, droughts, pests outbreaks, infectious diseases, health effects, etc.), and substitution (how easily a good or service, particularly the non-market goods and services, can be replaced by another). My sense is that economic studies that suggest climate change will bring net economic benefits tend to overlook the highest risk elements of climate change, assume high levels of adaptive capacity, a low discount rate, and focus exclusively on the more easily quantified marketed goods and services, particularly things like agriculture and shipping. This excludes the non-market goods and services that I mentioned earlier, upon which agriculture and other economic activity often depends. This means, in my view, that the sandbox they're play in is just too small. As a result, they miss a large fraction of the potential costs. Studies that attempt to include non-market goods and services tend to have much higher costs. However, including non-market goods and services is tricky because it isn't easy to assign value to goods and services that aren't traded in markets. For more on estimates of the damages done by emitting greenhouse gases, I'd recommend an article by Richard Tol (http://www.fnu.zmaw.de/ fileadmin/fnu-files/publication/tol/enpolmargcost.pdf). That said, I think Richard's conclusion underestimates the damages of emitting greenhouse gases by largely dismissing the damages to non-market goods and services. Paul On Jul 11, 9:26 pm, James Annan <[EMAIL PROTECTED]> wrote: > [EMAIL PROTECTED] wrote: > > James, > > > I think you've misunderstood (and as a result misrepresented) what I > > said. > > > I said that people, and the natural systems that we depend on, are > > heavily adapted to our current climate. I did not say, and wouldn't > > say, that we are optimally adapted to the current climate. > > > You also seem to misunderstand (and misrepresent) what Andrew Dessler > > said on his blog. He said the current climate is optimal, not that > > humans are optimally adapted to current climate. > > Well, I'm having a great deal of difficulty in making much sense of the > term "optimal", since it can only (at best) have meaning in the context > of an existing social, economic and technological background. And since > these are always changing, so is the "optimal" level of adaptation. > > > These are very different claims. The reason that current climate is > > likely optimal for human society is because we, and the physical and > > natural systems that we depend on, are so heavily adapted (though sub- > > optimally) to that climate. > > Your claim that the current climate is "likely optimal" is I believe > flatly contradicted by much of the economic literature, including even > (some of?) the curves in Stern, which imply modest benefits from modest > warming. As I've mentioned here before, the large losses assigned to > greater climate changes are largely based on sensitivity analyses that > impose a significant climate change on an existing infrastructure > without accounting for changes in the social, economic and technological > background, even when these are certain to be large (and may in many > cases be aimed at improving our adaptation to the climate). > > One of the most obvious and striking examples is food production. Just > compare how recent historical changes in yield compare to the estimated > effects of climate change - the latter is completely dwarfed by the > former. Projections of X million (billion) in hunger which make no > attempt to account for the realities driving food production are simply > not credible IMO. It is not a linear system and climate impacts are not > simply external and additional to everything else. > > > In short, we're not optimally adapted to our current climate, but > > we're better adapted to current conditions than we are to any other > > climate. > > Rather than merely re-stating your claim, how about supporting it? > > IMO in reality it's a much more subtle problem, concerning the rate of > change, how this compares to economic and technological progress, and > the time scale that infrastructure persists for anyway. > > To put it in concrete terms, housing in 2100 will depend on social > structure, technology/materials, and economics every bit as much as > climate, and we don't need to adapt to any of these given that my house > will surely be knocked down by 2040 in any case. > > James --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups Global Change ("globalchange") newsgroup. 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