List: cc Drs. Caldeira and Rau
1. I hope we can have some comment on last week's release of the NAS -
Royal Society report entitled:
A Discussion on Climate Change: Evidence and Causes
It can be downloaded for free at
http://nas-sites.org/americasclimatechoices/events/a-discussion-on-climate-change-evidence-and-causes/
I had been relatively happy with it until yesterday when a friend noted
it seemed to be arguing for irreversibility in the answer to the last question
(#20) - which showed no hint of carbon dioxide removal as an option. The entire
text for Q20 reads (emphasis added):
"If emissions of greenhouse gases were stopped, would the climate return to the
conditions of 200 years ago?
No. Even if emissions of greenhouse gases were to suddenly stop, Earth's
surface temperature would not cool and return to the level in the
pre-industrial era for thousands of years. If emissions of CO2 stopped
altogether, it would take many thousands of years for atmospheric CO2 to return
to 'pre-industrial' levels due to its very slow transfer to the deep ocean and
ultimate burial in ocean sediments. Surface temperatures would stay elevated
for at least a thousand years, implying extremely
long-term commitment to a warmer planet due to past and current emissions, and
sea level would likely continue to rise for many centuries even after
temperature stopped increasing [Figure 9]. Significant cooling would be
required to reverse melting of glaciers and the Greenland ice sheet, which
formed during past cold climates. The current CO2-induced warming of Earth is
therefore essentially irreversible on human timescales. The amount and rate of
further warming will depend almost entirely on how much more CO2 humankind
emits. "
2. There is also a figure associated with this taken from a paper by
Zickfeld etal, found at:
http://www.elic.ucl.ac.be/modx/users/thierry/articles/2013_Zickfeld_et_al_JClim.pdf
which does talk about negative emissions, albeit not very positively. This
perhaps justifies the above term "essentially", but I still feel that a quite
pessimistic and gloomy outlook is given, that should seem unjustified to anyone
believing in CDR as a necessity and possibility (as I do).
3. The public release event last week of 1.5 hours can be viewed at
https://vimeo.com/88282420 . Four of the principal authors (Brian Hoskins,
Eric Wolff, Benjamin Santer, Inez Fung) gave brief comments on the report and
the process - in response to questions from a reporter and maybe 10 from an
audience at NAS headquarters. They all responded fine, but see one question
below.
4. Re Geoengineering being something to consider, Hoskins and Fung
answered a question in the 63 - 68 minute timeframe using the word, saying it
was the fourth of four actions that could be taken. The report says (last
page):
"....or they can seek as yet unproven 'geoengineering' solutions to counteract
some of the climate changes that would otherwise occur. "
They apparently wanted to be sure that the audience in the room knew that they
intentionally did not talk about either SRM or CDR. They emphasized that the
graph in Question 20 makes no mention of either SRM or CDR because they didn't
want to get into those topics. But I now interpret (I hope correctly??) that
irreversibility was being ruled out, as they apparently would include CDR as
part of geoengineering. My preference is that they had said something about at
least afforestation/reforestation (Jim Hansen's approach to CDR) - as nice
credit was give about Hansen's early warnings.
5. Other questions were on a major release arctic methane release.
Near the 69 minute mark there was question on costs - but no specific answers
6. Dr. Fung said (my version, not from a transcript) just before the
96 minute mark (after a question suggesting 25%-40% CO2 removal):
" Because we have put this much heat into the system - removing that CO2,
you still would have that heat in the system. It would take a very long time.
And so we would still be warmer than in 1800."
This indicates to me that it could be that she truly believes in
irreversibility. That one can reduce CO2, but not temperatures - which, if
true, would argue against CDR. But I don't believe such irreversibility to be
true, and I am hoping she doesn't either.
a. One piece of counter-evidence is from Drs. Cao and Caldeira in
http://iopscience.iop.org/1748-9326/5/2/024011/fulltext/, showing a rapid fall
in surface temperature after a hypothetical complete removal of CO2.
b. Another is similar by Dr. Andrew Lacis in
http://www.giss.nasa.gov/research/briefs/lacis_01/
c. Another is in several analyses by Dr. Hansen. One, showing
rapidly falling temperatures after afforestation in figure 9 (with CO2 decline
in Figure 5) in:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0081648
7. I repeat that overall the report is helpful in providing counter
evidence to climate deniers. But this is to hope that others can comment on
how else to interpret Dr. Fong's comment at the 96 minute spot. I am sure she
knows several orders more in magnitude than myself about almost any climate
topic, but I fear that those arguing against CDR will find comfort in her words
and the above answer to Q 20. Can anyone offer a good explanation of these
"anti-CDR" (pro-irreversibility) remarks? I note for Dr. Rau (who has
complained on this list about "irreversibility") that Dr. Susan Solomon is a
co-author of this new report.
Ron
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