Climate Science and the Stern Review

Fundamentals of the climate science dispute and common misunderstandings of some issues raised about Part 1 of the Dual Critique of the Stern Review [Vol. 7, No. 4] are discussed. One consideration is that a distinct anthropogenic greenhouse gas signal has not yet been identified within natural climate variations. The slight warming that has occurred in the late 20th century, falling within previous natural rates and magnitudes of warming and cooling, is a priori unalarming. Empirical evidence shows that the warming effect of increasing carbon dioxide at the rates of modern industrial emission and accumulation is minor, noting the established logarithmic relationship between gas concentration increases and warming. No global increase in temperature has occurred since 1998 despite a 15 ppm (4%) increase in carbon dioxide concentration, and an expectation of continued warming even at constant CO2 levels. The key issue is assessment of risk, but that includes the risk of future coolings as well as warmings, as well as their significance relative to other factors. This is why an adaptive policy towards climate change is the most sensible response option.