Climate engineering a review of aerosol approaches to changing the global energy balance

Abstract

As global greenhouse warming continues to intensify, it is likely that demands to employ technologies of climate engineering will become increasingly insistent. This paper addresses the possibility of 'canceling' the radiative effects of the increasing greenhouse gases through solar reflectors. Two promising approaches, according to COSEPUP (1992), are the employment of aerosols in the stratosphere, directly as reflectors, or in the troposphere, for the 'seeding' of clouds to increase cloud amounts and brightness. Besides technological and economic feasibility, such schemes could be relatively reversible, and describing their impact may be within the reach of future scientific study.The climate system is not yet sufficiently understood for such actions to be warranted. However, there is considerable potential for an increased understanding of what such actions might do through the study of the role of similar aerosols already added to the climate system. In particular, the most intense volcanoes (e.g. Pinatubo) supply the stratosphere with enough aerosol over a period of a year or two to cancel out greenhouse warming from a resulting doubling of carbon dioxide. Furthermore, the addition of sulfate aerosols to the troposphere from the burning of fossil fuel may already be canceling out globally up to half of the greenhouse-gas warming. These comparisons suggest that at least 10 times as much sulfate aerosol would be needed in the troposphere as would be needed in the stratosphere for a comparable climatic effect. A better understanding of the role of the alreadypresent aerosols is a prerequisite for further progress in the use of aerosols for climate engineering. The links between the horizontal and vertical distribution of radiative sources and sinks and various atmospheric feedback processes, especially those related to the hydrological cycle and the consequent global and regional responses, are also needed.

Geoengineering: Encouraging Research and Overseeing Implementation

“…Thus, Dickinson (1996) said "As global greenhouse warming continues to intensify, it is likely that demands to employ technologies of climate engineering will become increasingly insistent." Similarly, people in those regions or nations who feel most threatened by the environmental problem will be most willing to use technological intervention (Kellogg and Schneider, 1974;Cicerone et.…”

The effects of deforestation on the hydrological cycle in Amazonia: a review on scale and resolution

“…Such anomalous circulations are presently being generated on the mesoscale, but, since they may evolve to higher scales (Baidya Roy et al, 2003), they must in fact be adequately represented by AGCMs through their parameterization schemes (Bonell, 1998). However, despite the intense research on this topic (Avissar, 1992;Henderson-Sellers and Pitman, 1992;Koster and Suarez, 1992;Dickinson, 1996;Liu et al, 1999, among others), a consistent representation of these processes has not been widely adopted by the macroscale modeling community yet. The parameterizations employed by the current generation of AGCMs tend to rely only on the quantification of turbulence effects, neglecting the influence of the heat fluxes associated with anomalous mesoscale circulations (Baidya .…”

An empirical model of global climate – Part 1: A critical evaluation of volcanic cooling

“…The possibility of geoengineering of climate via injection of sulfur to the stratosphere has a long history, starting with Budyko (1974), followed by a remarkably detailed and prescient chapter entitled "Geoengineering" in a National Academy of Sciences report (NAS, 1992), as well as papers by Dickinson (1996) and Schneider (1996). The suggestion by Crutzen (2006) that "if sizable reductions in greenhouse gas emissions will not happen and temperatures rise rapidly, then climatic engineering" by artificial enhancement of stratospheric sulfate could be "the only option available to rapidly reduce temperature rises and counteract other climatic effects" led to a widespread renewal of interest in geoengineering, undoubtedly due to the prominence of Paul Crutzen, but also because cooling after the eruption of Pinatubo had been so well studied by the time his paper was written.…”