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Global climate change is occurring at an
accelerating pace, and the global greenhouse gas (GHG)
emissions that are forcing climate change continue to
increase. Given the present pace of international actions,
it seems unlikely that atmospheric composition can be
stabilized at a level that will avoid "dangerous
anthropogenic interference" with the climate system, as
called for in the UN Framework Convention on Climate Change.
Complicating the situation, as GHG emissions are reduced,
reductions in the offsetting cooling influence of sulfate
aerosols will create an additional warming influence, making
an early transition to climate stabilization difficult. With
significant reductions in emissions (mitigation) likely to
take decades, and with the impacts of projected climate
change-even with proactive adaptation-likely to be quite
severe over the coming decades, additional actions to offset
global warming and other impacts have been proposed as
important complementary measures. Although a number of
possible geoengineering approaches have been proposed, each
has costs and side effects that must be balanced against the
expected benefits of reduced climate impacts. However,
substantial new research is needed before comparison of the
relative benefits and risks of intervening is possible. A
first step in determining whether geoengineering is likely
to be a useful option is the initiation of research on four
interventions to limit the increasing serious impacts:
limiting ocean acidification by increasing the removal of
carbon dioxide from the atmosphere and upper ocean; limiting
the increasing intensity of tropical cyclones; limiting the
warming of the Arctic and associated sea level rise; and
sustaining or enhancing the existing sulfate cooling
influence. In addition, in depth consideration is needed
regarding the governance structure for an international
geoengineering decision-making framework in the event that
geoengineering becomes essential.
