Comments and Questions

Overall assessmentI am not the person to judge the analytical results. There are many ad hoc assumptions, however, without much justification. The paper is presented as a paper about climate change. The model, on the other hand, has little to do with climate change. At two points, assumptions are made that are in clear contrast to the empirical knowledge about climate change. At one crucial point, the write-up is so muddled that it is impossible to compare the current paper to previous papers. (See specific comments). The authors do not attempt to compare their results to previous work. Indeed, they seem to be unaware that their conclusion (climate change is a problem of weak sustainability) is in sharp contrast to previous studies (Fankhauser, Mendelsohn, Nordhaus, Pearce, Tol) who conclude the economic impact of a century of climate change is comparable to a year or two of economic growth. I cannot recommend publication of the paper in its current form. The authors can do one of two things. Either they present the paper as a theoretical paper and remove all references to climate change as well as the empirical part. Or they make sure that their empirics is reproducible and correct (to the extent that we know what that is), and compare the results to previous studies and explain if and why this paper deviates from the received wisdom. Specific commentsScenaria > scenarios (pls switch on your spell checker – this is not a referee’s job) Footnote 3: Please cite academic papers rather than policy reports. You would find, by the way, that the academic literature does not support your alarmism. Equation (pls add equation numbers): With a Cobb-Douglas production function, emissions are essential. There is no empirical support for this assumption (e.g., Edmonds, Richels, Weyant), but it does affect your results. Equation (13) does not describe the carbon cycle (e.g., Maier-Reimer and Hasselmann, 1987). Equations (10) and (11): The damage function is ad hoc and very different than the damage functions one would find in the literature on this subject (e.g., Fankhauser, Mendelsohn, Nordhaus, Tol). Warming is logarithmic in concentrations. Although damages are more than linear in warming, utility is again sublinear in damage. I therefore do not understand the assumption γ>1. Table (pls add table number): β is not the marginal damage in the unnumbered equation above. What should I believe? Table 3a cannot be interpreted as it stands. Yet, your main results depend crucially on your assumptions about β. I read Tvouvelekas et al., which uses Tol’s (2005) GLOBAL, MARGINAL, MONETARY estimates. If you are using marginal estimates, you assume linearity that is γ=1 (as you do) – but Tol’s linearity is in money and emissions, not in utility and concentrations. If you are using monetary estimates, how can you add them to utility as in Eq (10-11)? If you are using global estimates, how did you translate them to the national numbers in Table 3a? Clearly, you did not use just an inverse of per capita income in Table 3a. Tvouvelekas, the alleged source of Table 3a, does not have these numbers either. Table 1: Please add descriptions for the symbols. Please revise the definition of significant digit. Tvouvelekas et al. is FEEM 38.07