*Methane accumulation*
Sent from my iPhone Dear Colleagues,
Three posts are copied below from a thread from the recent NOAC meeting (that includes many more posts) that I've been asked to share to other "community" lists.
Best, Ron
Dear Colleagues,
My mistake in chat:
Doug MacMartin was not a co-author, but did reply to John N on this
issue. As this came up in today's NOAC meeting as well I'm taking the
liberty of copying Doug's response below (and cc'ing him in the event
that he is not on the NOAC list).
Best, Ron
Daniele Visioni wrote a paper on methane under SAI in 2017;
https://acp.copernicus.org/articles/17/11209/2017/
Conclusions are a little hard to interpret from that paper, but yes, it’s understood that methane
lifetime would go up relative to not injecting (not just from
UV photolysis); that would then require more injection to compensate
for the increased RF from CH4, Dan’s estimate when I’ve asked him is
that that increase is of order 10% (so not negligible, but certainly not
a “major” problem). I’d put this in the category
of things that need more research to better quantify.
Re
UV, don’t forget that Sasha’s study was with GLENS, so with 4C of
cooling from SAI (i.e., in a world in which we’d probably all be extinct
if we didn’t have
SAI). So a 1C cooling (which would still be a pretty big program)
would be roughly ¼ of the UV impact. Also, given that strat ozone has a
“super-recovery” under climate change, reductions in UV relative to
that future world are still potentially increases
relative to today (see, e.g., fig 3 in
https://www.pnas.org/doi/10.1073/pnas.2202230119, which doesn’t
have the UV plotted, but does have high latitude SH ozone (the SH being
where the effect is larger than the NH); the scenarios that cool by ~1C
have ozone levels in 2070 that are still higher
than today.
doug
Dear Michael et al.,
I agree that no government
yet has (to my knowledge) authorized the piloting and testing of initial
SAI or any other form of direct climate cooling with potential global
impact. The conventional wisdom appears to be that the risks are too
great right now and that further research is necessary. However, I've
yet to see a study that these "great risks" of initial piloting of
deployment more than offset the clear and evident risks of not
implementing global cooling as soon as possible, that rapid global
cooling could mitigate. As far as i can tell current (mostly modeling)
assessments of potential SAI risks of Ozone depletion, Monsoon
interference, and increased Methane are all mixed and relatively
moderate compared to the continued run toward the cliff that pathway
that we are now on with a mitigation and draw down only approach.
I think Doug MacMartin's post (that I copied earlier in this thread) covers some of the most recent research on potential Methane depletion.
On Ozone depletion here's some of the details on the decidedly mixed Montreal Protocol report on SAI (sent 5/17 to the usual lists):
The report focused on a spring injection of SAI in Antarctica
(where the Ozone hole is
largest) and found in model simulations, after 20 years of SAI
sufficient to reduce global cooling by 0.5 C, loss of ozone in
Antarctica in October similar to losses in the 1990s that if continued
would delay ozone hole recovery by 25 to 50 years, but less loss if SAI
is
started later, and for larger applications enhancement of Ozone in the
winter in NH
mid-latitudes.
Details from the ES Chap. 5, p. 21-22 report below:
"Additional ozone depletion due to SAI is simulated in
spring over Antarctica, with magnitudes dependent on
the injection rate and timing. Simulations of strong SAI
show an increase in total column ozone (TCO) in mid-lat-
itudes (40–60°N) in the winter Northern Hemisphere.
º For October over Antarctica, SAI simulations that achieve
a global mean surface cooling of 0.5 °C in the first 20
years, show a reduction of TCO of around 58 ± 20 DU,
assuming 2020–2040 halogen conditions. This reduc-
tion brings TCO values close to the observed minimum in
the 1990s. Less ozone loss would be expected for a later
SAI start date, when halogen concentrations are project-
ed to be lower.
º Beyond the first 20 years, the continued application of
strong SAI, to offset almost 5 °C of warming by 2100, re-
duces Antarctic ozone in October
by similar amounts (55
± 20 DU) throughout the 21st century despite declining
abundances of ozone-depleting substances (ODS). In
this case, ozone hole recovery from ODSs is delayed by
between 25 and 50 years. A peakshaving scenario po-
tentially leads to less ozone depletion.
º Under stronger SAI scenarios, ozone is significantly
enhanced in NH mid-latitudes in winter owing to strato-
spheric heating from injected sulfur, which leads to in-
creased equator to poleward transport of ozone.
º Ozone loss within the Arctic polar vortex has not yet
been robustly quantified for SAI."
Is
anyone aware of any other risks that could rule out cautiously piloting
SAI (for example in Polar regions per "the Cornell School" led by
Doug)?
Let
me add that my understanding is that one of the problems with basing
everything on modeling and limited lab and atmospheric testing is that
atmospheric systems are so complex that it would be impossible to
definitively (at a 95% confidence level) rule out all potential adverse
unintended consequences. The best way to "test" appears to be thus to
conduct limited pilots that gradually scale up and adjust and modify as
more real time data is obtained. We are after all talking about
mimicking (in a more gradual and deliberative way) the millions of tons
of sulfur aerosol that has been injected into the stratosphere by
volcanoes naturally for as long as we've been on this planet and much
longer! This is not after all "nuclear radiation" but "natural" sulfur
aerosols! This is not to say of course that modeling and other research
should not continue, it's just the idea that purely researching without
testing deployment for another 10 years or so (as David Keith opined in
HPAC discussion) before then potentially going "all in" for deployment
if global conditions become very extreme is a good strategy?
I
of course defer to Doug, Michael MacCracken and others are much more
knowledgeable about all this than myself - but per Mike M's view (I
believe - if you see this Mike please correct me if I'm
misinterpreting!) it is a terrible mistake for policy to determined
based on "scientific criteria" (like less than 5% risk). Rather, policy
should be based on reducing catastrophic risk (even if it's low
possibility) like crossing tipping points that we are much greater risk
of crossing as we warm above 1.5 and 2.0 etc. Doug, I don't know if
you're of the same view, but I certainly agree with everything in your
most recent post on this thread (that I just saw!).
Needless to say, I welcome further evidence and discussion on any of these points!
Best, Ron
Dear Michael et al.,
Agreed that anything
impacting the globe has the potential to cause discontent and conflict.
Unfortunately though, we’re in a situation that can only be solved
globally. (In fact, I believe that one of the key reasons that the heavy
lift to achieve timely and massive GHG reduction and draw down has
unfortunately failed is due to the collapse of the Kyoto Protocol
mandatory cap and trade regime and its replacement with a voluntary NDC
regime: https://www.cpegonline.org/post/our-two-climate-crises-challenge.)
So
we have to find a way to implement a global cooling solution (that will
probably have to be complemented early on and later by many more global
and local cooling efforts using different methods: https://pdfhost.io/v/pR4xEbZzO_The_Case_for_Urgent_Direct_Climate_Cooling040223).
I think part of the block against SAI that you (and many others) are
expressing is due to a "big bang" conceptualization (do a lot of
research and then proceed to rapid global implementation) that in my
(and Mike MacCracken and I think Doug MacMartin and "the Cornell School"
of SAI) is not a good way to think about implementation. Rather, I
think (I believe following MacCracken and "the Cornell School) a more
realistic and advisable method is to start very gradually with pilot SAI
baby steps in the poles (lower tropopause) in the spring and so
that it will fall out in the fall (aerosols likely to fall-out more
quickly within months rather than years in the poles) that would
increase albedo in the most important sun lit summer months and not
obstruct long-wave release in the dark winter months. This would
hopefully reduce critical Arctic sea ice melting and "Polar
Amplification" that is a key source of jet stream meandering and slowing
and recent extreme climate events (See Greta (ed) 2022 section 2.6 by
Jennifer Francis for recent direct evidence - endnotes and references
at: https://theclimatebook.org/en-us/).
It
has recently occurred to me that a good model for this kind of
collaboration might be the international space station that includes the
work of a large group of nations.
(From Wikipedia: NASA (United
States), Roscosmos (Russia) and the European Space Agency are the major
partners of the space station and contribute most of the funding;
other partners are the Japanese Aerospace Exploration Agency and the
Canadian Space Agency).
This
could start small over the poles with a near term goal of reducing
global extreme climate events, build trust, transparency, and grow in
partners though include mostly countries with the resources and
capabilities to contribute on which the rest of the world would be happy
to 'free ride' especially if there were clear reductions in climate
catastrophes. As the initial focus would be the poles I think the
potential for opposition and conflict would be reduced. As this
"International Global Direct Climate Cooling Agency" gained more trust,
confidence, and partnerships, from countries around the world it could
(if the SAI was working and beneficial) gradually expand to global
coverage.
(From Wikipedia again: the ISS has been described as the most expensive single item ever constructed. [82]
As of 2010, the total cost was US$150 billion. This includes NASA's
budget of $58.7 billion ($89.73 billion in 2021 dollars) for the station
from 1985 to 2015, Russia's $12 billion, Europe's $5 billion, Japan's
$5 billion, Canada's $2 billion, and the cost of 36 shuttle flights to
build the station, estimated at $1.4 billion each, or $50.4 billion in
total. Assuming 20,000 person-days of use from 2000 to 2015 by two- to
six-person crews, each person-day would cost $7.5 million, less than
half the inflation-adjusted $19.6 million ($5.5 million before
inflation) per person-day of Skylab. [83])
Feedback on this is most welcome!
Best, Ron
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