An Optimal Degree Of Global Warming

Global warming issues are hard to resolve, in part because their discussion is so open-ended. Contemporary discussions have concentrated on ways to mitigate or reduce global warming, rather than looking beyond those objectives. In the prevailing estimates of the costs and benefits of global warming, there is an implicit assumption that there is some optimal degree of global warming, or some optimal temperature for the Earth, and that there is only one direction to move in attaining it — to mitigate or stop the current trend. However, do we really know what this temperature is?

R. Lal has implied that identifying an optimal degree of warming is possible when he noted that average global temperature has ranged between -18° C to +15°C. That is quite a wide range, and if there are costs and benefits in going from one average temperature to another, then there must be an optimal temperature for the Earth — something that C. Rosenzweig referred to, when commenting on my proposition, as a stabilization level.

Certainly, if one is willing to commit significant public and private resources to affect the global temperature, then why should those resources not be committed to moving the world toward what would be an optimal temperature? In fact, when establishing quotas and other targets for policies designed to affect global warming, some target temperature would seem to be an imperative. Is it appropriate to expend resources to mitigate or reduce global warming when we have no notion of the ultimate goal?

I would argue that it makes no sense to insist on mitigating policies without having some notion of the ultimate target. The failure to establish such an optimal temperature follows from the tendency in much of the discussions of global warming to ignore people — similar to the approach by many environmentalists. Yet surely, if Nordhaus can estimate the costs and benefits of global warming, we can move beyond those calculations to ascertain some optimal temperature for the Earth.

It may be helpful to introduce the concept of an optimal global temperature as we address these problems, even if we currently lack the data to estimate the optimum as a practical matter. First, it would focus our attention on assembling the necessary data and undertaking the appropriate analyses to arrive at such a conclusion, which should give us a better understanding of all the important issues involved. Second, it would help us avoid committing massive resources in what could turn out to be misguided directions.

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