HR: 11:00h
AN: PA52A-03    [Abstracts]
TI: Probabilistic analysis of climate stabilization targets and the implications for precautionary policy
AU: * Baer, P
EM: pbaer@socrates.berkeley.edu
AF: Energy and Resources Group UC Berkeley, 310 Barrows Hall, Berkeley, CA 94720 United States
AB: A cruicial influence on precautionary policy is the uncertainty of the climate sensitivity - the equilibrium response of the global mean surface temperature to a doubling of CO2 . The climate sensitivity has been represented in the published literature by a wide variety of descriptions, including both formal probability density functions (PDFs) and simple ranges. How to utilize these PDFs and quasi-PDFs is a crucial question at the science-policy interface. Conventional risk analysis methods can be applied, including monte carlo methods with a probabilistic treatment of the climate sensitivity. However, there is no obviously correct way perform such analyses; slightly different framings of the policy question (e.g., targets for CO2 or all GHGs) lead to different modeling schemas. In this paper, I present three simple models that use a range of climate sensitivity PDFs to generate PDFs for the "implied equilibrium temperature" (the hypothetical equilibrium temperature if radiative forcing were to stabilize at a given level) for different GHG stabilization policies. The first takes a fixed value of radiative forcing or CO2-equivalent concentration; the second takes a fixed CO2 concentration and a stochastically defined value for net non-CO2 forcing; and the third takes a fixed increase in radiative forcing and a stochastic value for current net forcing. In addition to temperature PDFs for different policies, I calculate the policy targets implied by given temperature/probability thresholds. These indicators provide the necessary framework for a meaningful debate on precautionary policy, in which such a temperature/probability threshold is a logical policy goal. Finally I show the policy implications of various precautionary targets, particularly those using the widely proposed target of no more than 2§C increase above pre-industrial temperatures. I demonstrate that a high probability of staying below 2§ requires stabilization levels on the order of 400 ppm CO2-equivalent, far below the stabilization levels currently considered realistic.
DE: 6309 Decision making under uncertainty
DE: 6324 Legislation and regulations
DE: 1600 GLOBAL CHANGE (New category)
DE: 1610 Atmosphere (0315, 0325)
SC: Public Affairs [PA]
MN: 2004 AGU Fall Meeting