Hi Doug--In response to your Nov 4 post below, I am all for learning,
but the problem with waiting and waiting is that the Earth will keep
warming and warming and impacts will keep growing and growing--including
especially ones that are or near irreversible, such as to biodiversity
and commitment to sea level rise.
If the goal were, during this 20-year learning time, only to reduce or
offset year-by-year warming as might be done, based on our understanding
of volcanic effects, using quite small annual increments to the
stratospheric sulfur loading, and basically iterating as we go on
something like 5-year running averages, we would very likely be in a
much more favorable situation to evaluate how to proceed, both having
better model analyses and having some experience to work with. If we
find the 20-year accumulation is worse than ongoing global warming with
GHGs or that mitigation is working particularly well, the stratospheric
injection level could be gradually reduced instead of continuing with
ongoing augmentation. While there would of course be uncertainties, it
is not really clear that they would be more serious than the increasing
changes and impacts that are occurring. It just seems to me that to do
nothing while continuing with research just lets the situation get worse
and then the cure having to be so much stronger than deployment itself
could be problematic.
If, as Santer et al suggest, early 21st century rate of warming was
slowed by the cooling influences of small volcanic eruptions that
injected amounts that were barely noticeable even with advanced
instruments and really not at all noticeable by the general public, I'd
suggest that we actually have a natural analog of the type of influence
that I am suggesting be pursued. And, in that we will be learning along
the way through the 20-year research program (let's assume that the
research is funded), so it just seems, as noted above, that the
uncertainties associated with such an approach would not be less than
the impacts and uncertainties of deferring all intervention efforts
until some probably pretty arbitrary level of understanding in the future.
Regarding my favoring of regionally focused alterations, I would make
that a research priority, but I'd suggest that the earlier one started
injecting enough sulfur to offset each year's forcing increment or so,
the better--just thinking that, in the type of relative risk framing
that I view as appropriate to the situation given where we are, that,
with mitigation ramping up virtually everywhere (and the US doing
somewhat well despite the Administration's mistaken actions), starting
very modestly with stratospheric aerosol climate intervention could
really help in making sure that the situation is not so bad by the time
we learn enough to "make reasonably informed decisions" (whatever that
means) that we will be unable to avoid significant overshoot of the
global average temperature without such aggressive intervention that
we'll be suffering from both the growing impacts and then the supposed cure.
At the very least, I would think a good case could be made for such an
effort.
Best regards, Mike MacCracken
On 11/4/17 11:43 AM, Douglas MacMartin wrote:
Both SAI and MCB probably need of order of 20 years of research before we could make
reasonably informed decisions; both have a long list of unknowns. (In the case of MCB,
we don't even really know if it "works" in any meaningful sense of the word,
because cloud-aerosol interactions are too uncertain today, so we really don't know
whether there is a useful fraction of cloud meteorological conditions in which the albedo
is significantly enhanced. We should all really really hope that it doesn't work very
well, because if it doesn't, that means the indirect aerosol effect is smaller than
current best guess and climate sensitivity will be on the low end...)
(And, of course, at the current level of worldwide funding, that "20" above is
probably off by a few orders of magnitude.)
-----Original Message-----
From: [email protected] [mailto:[email protected]]
On Behalf Of Michael Hayes
Sent: Saturday, November 04, 2017 10:00 AM
To: geoengineering <[email protected]>
Subject: Re: [geo] Can anyone offer a CE perspective on this SLR article?
Holly and List,
The use of sulfur needs proper polar field level testing. Testing is planned
yet may not be done in areas prone to Polar Stratospheric Cloud formation. Time
of the season is also of the essence for testing.
Until that is done, SAI has a large question to answer; in general terms.
MCB, used in key areas, is a critical first step. There should be no deflection
at that engineering level. Once MCB paves the way, other marine capable systems
can gain traction.
What marine engineering minded person or institution would not give Steven's
word heavy weight? This is a marine issue.
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