HR: 08:15h
AN: B31D-02    [Abstracts]
TI: Optimal Timing of Oceanic, Geological and Biological Carbon Sequestration to Safeguard Climate
AU: Gitz, V
EM: gitz@centre-cired.fr
AF: CIRED - Centre International de Recherche sur l'Environnement et le Developpement, 45 bis avenue de la belle Gabrielle, Nogent sur Marne, F 94736 France
AU: * Ambrosi, P
EM: philippe.ambrosi@cea.fr
AF: LSCE - Laboratoire des Sciences du Climat et de l'Environnement, L'Orme des merisiers, Bat 701, Gif sur Yvette, F 91191 France
AU: * Ambrosi, P
EM: philippe.ambrosi@cea.fr
AF: World Bank DECRG-IE, 1818 H street, NW, Washington, DC 20433 United States
AU: Ciais, P
EM: philippe.ciais@cea.fr
AF: LSCE - Laboratoire des Sciences du Climat et de l'Environnement, L'Orme des merisiers, Bat 701, Gif sur Yvette, F 91191 France
AU: Orr, J
EM: james.orr@cea.fr
AF: LSCE - Laboratoire des Sciences du Climat et de l'Environnement, L'Orme des merisiers, Bat 701, Gif sur Yvette, F 91191 France
AU: Magne, B
EM: bertrand.magne@univ-tlse1.fr
AF: LERNA - Laboratoire d'Economie des Ressources Naturelles, 21 allee de Brienne, Toulouse, 31042 France
AU: Hourcade, J
EM: hourcade@centre-cired.fr
AF: CIRED - Centre International de Recherche sur l'Environnement et le Developpement, 45 bis avenue de la belle Gabrielle, Nogent sur Marne, F 94736 France
AB: We address the issue of safeguarding climate in the presence of a cascade of uncertainties through a portfolio of mitigation options: emissions reductions (M), biological carbon sequestration (BCS), carbon capture and storage - both geological (GCS) and oceanic (OCS). Within a sequential decision framework (i.e. as uncertainties are progressively resolved with time), we use a global optimal control model, RESPONSE, to examine the relative advantages of the three sequestration options in lowering fossil fuel abatement expenditures. Moreover, we show to what extent these options offer additional flexibility for short- and long-term decision given uncertainties on climate sensitivity and ``safe'' climate targets. To do so, we compute the value of information regarding these uncertainties and assess the timeliness of learning (i.e. which uncertainty is more``urgent'' to resolve). Finally, we show to what extent short term optimal paths of fossil emissions abatement and carbon sequestration are robust to these uncertainties. We find that BCS, GCS and OCS are complementary both in alleviating the constraint on the energy sector and in tackling the uncertainties. BCS is used more in the short term as a brake whereas OCS and GCS are used more in the long term as a safety valve. In other words, a portfolio approach is preferable to an approach based solely on emissions reduction: with a fully- diversified mitigation portfolio, discounted global climate policy costs are up to 38% lower than with an abatement-only policy and discounted abatement costs decrease up to 54%. Short-term costs are lower, mainly (81%) thanks to BCS - a result relatively independent upon the emissions scenario. Long- term costs are mainly lower thanks to GCS or OCS, both options being concurrent. However, in the case of high-emissions scenarios (like A2), OCS proves highly helpful (up to 25% of A2 reference scenario cumulated emissions could be stored). Though marginal in duration given the opportunity cost to permanently immobilize lands, BCS proves helpful on short-term (when the rate constraint essentially bites) against all uncertainties. GCS and OCS, which deploy later and prove helpful against uncertainties that are pregnant on a longer term (like the magnitude constraint), or when they are supposed to be resolved in the long run. \begin{tabular}{ccccccc}\hline\hline &μlticolumn{3}{c} {early learning}&μlticolumn{3}{c}{late learning}
policy option&t2x&ryt&tmax&t2x&ryt&tmax
\hline M&1.64&6.32&1.24&2.22&7.81&4.46
M+BCS&1.05&4.44&0.84&1.50&5.55&3.29
M+GCS&1.51&5.91&0.80&2.02&6.90&2.47
M+OCS&1.62&6.02&0.89&2.13&6.93&2.47
M+BCS+GCS+OCS&1.02&4.22&0.59&1.45&5.07&2.04
\hline\hline \end{tabular} Table 1. The value of information in 1990 (T US90$) for the climate sensitivity (t2x), the rate constraint (ryt), the magnitude constraint (tmax) in early-learning (2030) and late-learning (2060) scenarios, under four policy options.53 wt.
DE: 0325 Evolution of the atmosphere (1610, 8125)
DE: 6309 Decision making under uncertainty
SC: Biogeosciences [B]
MN: Fall Meeting 2005