The termination problem that poses the biggest threat is the termination
problem related to fossil-fuel CO2 emissions.
Were we to terminate such emissions today suddenly, there would global
economic havoc ("threatening the food supply of billions of people"). Not
only that, but the climate effects of our CO2 emissions will last centuries
to millennia after emissions cease.
At least stratospheric aerosols can be terminated suddenly without directly
causing economic havoc, and climate effects of these aerosols are likely to
be undetectable within years after termination.
If CO2 emissions were to have the "termination problem" of stratospheric
aerosols, our climate problems would be far easier to solve.
___________________________________________________
Ken Caldeira
Carnegie Institution Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA
+1 650 704 7212 [email protected]
http://dge.stanford.edu/labs/caldeiralab @kencaldeira
On Mon, Apr 25, 2011 at 8:31 AM, Nathan Currier <[email protected]>wrote:
>
> I agree with Ken’s comments to the authors, but wonder whether this
> concentration on geoengineering’s ‘termination problem’ couldn’t be
> used to rethink possible limits on large-scale aerosol SRM to make it
> more palatable and acceptable? Someone once posted, either in a ‘moral
> hazard’ thread or another on governance, the idea of linkage – linking
> geoengineering to reductions in emissions. It was immediately shot
> down because it would seem to block all emergency interventions that
> most see as the prime raison d’etre of intervention.
>
> In discussing SRM’s ‘termination problem,’ one must keep in mind that
> we already have a very big aerosol ‘termination problem’ with CO2
> emissions reductions themselves. Mike MacCracken once in a personal
> correspondence mentioned some thoughts about how SO2 market forces
> could help – but that would really only help “smooth out” rapid
> changes for a while and couldn’t do much to blunt large losses of
> aerosol loading, and the large increase in RF that could follow them.
> Gore’s US “10 year plan” alone would have stressed the climate system
> 4x more than did US pollution controls in the 1980-2000 period (i.e.
> twice the sulfur loss in half the time), seen by some as a major
> contributor to accelerating of warming back then. It alone will likely
> justify the need for geoengineering. Could the two 'termination
> problems' be usefully linked?
>
> If one were to divide all SRM geoengineering into two –
>
> 1. highly localized emergency response engineering, initially geared
> towards preserving arctic
> conditions.
>
> 2. larger-time-scale technologies of broader, more global scope.
>
> then only 2. could really involve the kind of global “termination
> problem” that is the fear of the authors.
> Might it not make sense, then, from several perspectives, to create a
> linkage system for anything in 2., but not like that previously
> proposed – that is, not a linkage between the CO2 reductions
> themselves and the amount of geoengineered aerosols, but between their
> co-emitted negative forcers lost and the amount of SRM aerosols
> allowed into the geoengineering system? From whatever time the system
> starts one could back-date the load cap a little, perhaps even all the
> way back to whenever there was the highest loading in our recent past
> (and thus demonstrably relatively safe) – which would, at a guess.
> have been the early 1980s. There could be exceptions to the cap made
> for catastrophic climate emergencies.
>
> Forgive me if this rather obvious thought has been proposed already,
> but if not, couldn’t that help make SRM somewhat more palatable, in
> that it would put strict cap on the amount of SRM such that it is
> quite unlikely to be dangerous in its side effects on hydrology, etc.,
> (as long as we understand spatial and temporal distribution issues
> well enough and have a system for flexibly controlling them – and they
> certainly weren’t optimized before!), and then the amount of sudden
> warming worried about by these authors could never exceed what we
> would have been facing through a sudden emissions cessation anyhow.
>
> With such an approach, except for extreme emergencies, global SRM
> could only be introduced gradually to help keep the balance of
> positive and negative forcings somewhat as we have already experienced
> it (assuming future emissions are controlled, of course). There would
> still be the same “termination problem,” of course, but it would only
> be one gradually ‘taken over’ from the inherent one already in our
> current anthropogenically-engineered climate system. Hopefully, after
> several decades of combined emissions cuts and various forms of CDR,
> biochar, BECS, etc, we could turn it all off.
>
> Implicit in this is that other means than just “ big” SRM would need
> to be used for dealing now with the unfolding catastrophe in the
> arctic, and that would be 1. above. From previous posts it should be
> clear that I believe that the only reasonable path to dealing with
> this – which will likely very soon sink our whole ship – is going to
> have to include starting very soon a global-scale non-CO2 emissions
> reductions regime (methane/BC/O3 for example). I’m all for
> geoengineering there, too, but think it should be thought of along the
> lines of Pacala and Socolow’s stabilization wedges, a variety of
> smaller techniques invested in, lessening the side effect risks from
> any one of them, and done in conjunction with these targeted emissions
> cuts.
>
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