Poster's note: others challenge these arguments. Parker and Irvine dispute
the vulnerability of solar geoengineering to anything less than eg a
nuclear war. Keith et al. suggest it can be temporarily deployed

Solar engineering must take temperature debt into account
Andreas Oschlies




 PDF version

Solar geoengineering is a proposed method of climate engineering that aims
to reduce global warming using an artificial ‘sunscreen’ of aerosols in
Earth’s high atmosphere. As planning of the first field experiments gets
under way, any potential risks associated with the technology must be
transparently assessed and not downplayed or dismissed. One such risk of
solar geoengineering is its ‘temperature debt’ — the planetary heating that
would arise if maintenance of the artificial sunscreen was discontinued.

Modelling suggests that most of the world’s population could benefit from
this temporary sunscreen, compared with the adverse effects of unabated
climate change (a questionable reference state, in my view). However,
models also reveal the alarming rise in temperatures that could occur if
the screen of short-lived aerosols should suddenly cease to function for
any reason in the presence of high concentrations of long-lived greenhouse
gases (see H. D. Matthews and K. Caldeira *Proc. Natl Acad. Sci.
USA*104, 9949–9954;
2007 <>). This rapid warming would
pose a severe risk to ecosystems and society.

Even with the best planning to ensure steady operation of the technology,
its continuous safe functioning and maintenance cannot be guaranteed. Yet
it could take hundreds of years to safely phase out solar geoengineering
and achieve the same degree of cooling by reducing greenhouse-gas
concentrations. It is therefore imperative that, in the absence of a
fail-safe mode for solar geoengineering, the temperature debt is fully
accounted for in any assessments of this technology.

Nature 554, 423 (2018)
doi: 10.1038/d41586-018-02203-x

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