HR: 10:40h
AN: GC52A-03 INVITED    [Abstracts]
TI: Transient climate-carbon simulations of planetary geoengineering
AU: * Matthews, D
EM: dmatthew@alcor.concordia.ca
AF: Concordia University, 1455 de Maisonneuve Blvd W., Montreal, QC H3G 1M8, Canada
AU: Caldeira, K
EM: kcaldeira@globalecology.stanford.edu
AF: Carnegie Institution, 260 Panama Street, Stanford, CA 94305, United States
AB: Geoengineering (the intentional modification of Earth's climate) has been proposed as a means of reducing CO₂-induced climate warming while greenhouse gas emissions continue. Most proposals involve managing incoming solar radiation such that future greenhouse gas forcing is counteracted by reduced solar forcing. In this study, we assess the transient climate response to geoengineering under a business-as-usual CO₂ emissions scenario, using an intermediate complexity global climate model which includes an interactive carbon cycle. We find that the climate system responds quickly to artificially reduced solar insolation; hence, there may be little cost to delaying the deployment of geoengineering strategies until such a time as "dangerous" climate change is imminent. Spatial temperature patterns in the geoengineered simulation are comparable to pre-industrial, though this is not true for precipitation. Carbon sinks in the model increase in response to geoengineering: since geoengineering acts to mask climate warming, there is a direct CO₂- driven increase in carbon uptake without an offsetting temperature-driven suppression of carbon sinks. However, this strengthening of carbon sinks, combined with the potential for rapid climate adjustment to changes in solar forcing, leads to serious consequences should geoengineering fail or be stopped abruptly. Such a scenario could lead to very rapid climate change, with warming rates up to 20 times greater than present day. This warming rebound would be larger and more sustained should climate sensitivity prove to be higher than expected. Thus, employing geoengineering schemes with continued carbon emissions could lead to severe risks for the global climate system.
DE: 1600 GLOBAL CHANGE
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
DE: 1622 Earth system modeling (1225)
DE: 1626 Global climate models (3337, 4928)
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting