In this paper I comment on the reactions of William Nordhaus to a recent article of mine entitled "On Modeling and Interpreting the Economics of Catastrophic Climate Change" that appeared in the February 2009 issue of the Review of Economics and Statistics. My target audience here is PhD-level general economists, but this paper could also be viewed as a somewhat less technical supplement to my article, which some interested non-economist readers might conceivably find useful on its own account.
Climate change is characterized by deep structural uncertainty in the science coupled with an economic inability to evaluate meaningfully the welfare losses from high temperature changes. The probability of a disastrous collapse of planetary welfare from too much CO2 is non-negligible, even if this low probability is not objectively knowable. This paper attempts to explain (in not excessively technical language) some of the most basic issues in modeling the economics of catastrophic climate change. The paper builds to a tentative conclusion that, no matter what else is done realistically to slow CO2 buildups, economic analysis lends some support to undertaking serious research now into the prospects of "fast geoengineering preparedness"–as a state-contingent emergency option offering at least the possibility of knocking down catastrophic temperatures rapidly.
The proposal discussed in this paper is to levy a common charge on all emissions of greenhouse gases, worldwide. All countries would be covered in principle, but the proposal could be implemented with a much smaller number of countries, provided they covered most of the emissions. While all greenhouse gases should in principle be covered, this paper will address mainly carbon dioxide, quantitatively the most important greenhouse gas; extensions to other greenhouse gases could be made with little or (in the case of methane) much difficulty. The charge would be internationally adjusted from time to time, and each country would collect and keep the revenue it generated. This paper will discuss in turn the motivation for such a proposal, how it would be implemented, its likely economic effects, the relationship to energy security, the possibility of mixing an emission charge with other schemes to limit emissions, especially "cap-and-trade" schemes, and the negotiability of such an agreement.