HR: 11:20h
AN: GC52A-07    [Abstracts]
TI: Artificial Enhancement of Natural Forcings to Cool The Earth and Their Effects on the Climate System
AU: * Ammann, C M
EM: ammann@ucar.edu
AF: Climate and Global Dynamics Division National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, CO 80307-3000, United States
AU: Washington, W M
EM: wmw@ucar.edu
AF: Climate and Global Dynamics Division National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, CO 80307-3000, United States
AU: Buja, L
EM: southern@ucar.edu
AF: Climate and Global Dynamics Division National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, CO 80307-3000, United States
AU: Teng, H
EM: hteng@ucar.edu
AF: Climate and Global Dynamics Division National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, CO 80307-3000, United States
AU: Strand, W G
EM: strandwg@ucar.edu
AF: Climate and Global Dynamics Division National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, CO 80307-3000, United States
AU: Middleton, A
EM: adrianne@ucar.edu
AF: Climate and Global Dynamics Division National Center for Atmospheric Research, 1850 Table Mesa Dr, Boulder, CO 80307-3000, United States
AB: Natural climate variability has always existed and will continue to operate in the future. Current climate changes, however, are quickly exceeding the range that can be explained with natural factors both internal and external to the climate system. Anthropogenic modifications to the atmosphere and essentially all other components of the climate system are causing a rapid change in climate. Because of the speed and expected magnitude of changes, and because of the longevity of the already committed as well as future forcing (the greenhouse gases), various alternatives for "corrections" are being discussed in the climate community and their potential impacts have to be carefully assessed. Using the NCAR Community Climate System Model, we study the effects of two different approaches of how the Earth's energy balance could be altered to keep global climate from continued warming. One approach deals with a possible reduction of solar irradiance (e.g., achieved through a large number of reflectors in space that would divert sunlight away from Earth), the other considers maintaining an artificial sulfate "blanket" in the stratosphere (achieved through continuous injection of sulfur into the tropical stratosphere). These strategies mimic natural forcings of solar irradiance changes and the effects from explosive volcanism, both factors that are included in their natural setting in standard simulations of the recent past. Branching off the IPCC-AR4 assessment simulations we determine the necessary magnitude of artificial enhancement of these natural forcings that would required to counter a high-emission scenario (A2). These ensemble simulations done for both cases demonstrate that the required enhancement of natural forcing factors - and thus the anthropogenic changes expected under a high-emission scenario themselves - are far larger than their natural range. Moreover, our simulations with the fully coupled model allow us to document the significant spatial impacts of such artificially "stabilized" climate that could be expected under the two geoengineering scenarios. While global mean temperature can be "restored" to a specified level, some regional climates will be very different.
DE: 0370 Volcanic effects (8409)
DE: 1637 Regional climate change
DE: 1650 Solar variability (7537)
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1807 Climate impacts
SC: Global Environmental Change [GC]
MN: 2007 Fall Meeting