A Serious Look at Geo-Engineering
by David W. Keith and Hadi Dowlatabadi
published July 7, 1992
Possible responses to the problem of anthropogenic climate change fall into three broad categories; abatement of human impacts by reducing the climate forcings, adaptation to reduce the impact of altered climate on human systems, and deliberate intervention in the climate system to change the effects of anthropogenic forcing- geoengineering.
While they included geoengineering options, they failed to consider them systematically.
We present the beginnings of a more systematic analysis and urge a balanced research program on geoengineering.
We define geoengineering as actions taken with the primary goal of engineering (controlling by application of science) the climate system.
Geoengineering is the deliberate manipulation of climate forcings intended to keep the climate in a desired state, in contrast to abatement, which reduces anthropogenic forcing.
Speculation about geoengineering dates to the beginning of the century when Arrhenius  suggested that burning fossil fuels might help prevent the coming ice age.
Some technical possibilities for geoengineering were summarized by Dyson and Marland .
Since then, increased concern about climate change has generated more literature, but no systematic research program has emerged.
For example, the OTA report has a cursory description of two geoengineering options with no contextual discussion.
The NAS report contains a more substantial review, although it has significant technical omissions.
Neither provides a basis other than cost for comparing the options nor includes a discussion of the relationship between geoengineering and abatement.
We do not advocate geoengineering, but we offer these justifications for a more systematic evaluation of geoengineering options.
-Geoengineering may be needed if climate change is worse than we expect.
-It seems very unlikely that world greenhouse gas (GHG) emissions can be kept below - 40% of 1990 levels – a prerequisite for averting climate change in the long term.
Doubt about the prospects for cooperative abatement of global GHG emissions is a pragmatic reason to consider geoengineering, whose implementation requires fewer cooperating actors than abatement.
Thus geoengineering fills a unique niche because of its potential to mitigate catastrophic climate change.
To act as a fallback strategy, geoengineering must be more certain of effect, faster to implement, or provide unlimited mitigation at fixed marginal coset.
Our definition of “fallback strategy” is an extension of the term “backstop technology” used in energy systems analysis for a technology providing unlimited energy at fixed (usually high) marginal cost.