> We would much appreciate input from climate scientists to help us with
> this question.
> Humberto Llavador, University Pompeu Fabra, Barcelona
> John Roemer, Yale University
> Joaquim Silvestre, Univ of California, Davis
I am a (fairly knowledgable by now) amateur climatologist, being a
retired different sort of scientist and a long-time amateur
paleogeologist. That said, I have some rathr firm opinions about what
is actually required to produce some sane stability in the climate to
(approximately) restore the ideal conditions for agriculture and
silviculture enjoyed during the Holocene. (We have just left the
Holocene for the Anthropocene, a geologic interval that needs to be a
short as possible.)
After I proposed a level of 315 ppmv of atmospheris carbon dioxide,
for no better reasons than that is about the level enjoyed during the
1950s, Dr. James Hansen, GISS, proposed 300--350 ppmv as necessary to
maintain Arctic ice and, I think, Greenland ice. Let us use my
suggested 315 ppmv figure for calculations.
The estimate usually stated is that about 500 GtC of fossil carbon has
been added to the active carbon cycle since about 1750 CE, rasing the
CO2 concentration from 260 ppmv to 280 ppmv in about 1880 CE, about
315 ppmv in 1958 CE and 385 ppmv now. The current rate of addition
has been recently estimated to be 8.5 GtC per year and rising.
I assume next that the 8.5 GtC yearly addition can been forgone or
else permanently sequestered, along with any additional increases.
Assuming now constancy, it is easy to determine that it is necessary
to remove almost 350 GtC from the active carbon cycle to restore the
presumed ideal level of 315 ppmv.
For the sake of the health of the oceans, this ought to be done as
rapidly as possible. Unfortunately, upon estimating some costs for
carbon capture and sequestration, it seems that some decades will
likely have to pass. It might be able to accomplish such a goal by
2050 CE and certainly could be accomplished by 2075 CE.
Is that enough? I doubt it. My model is overly simple, not
accounting for the additional methane production now versus 50 years
ago. As I see no way to limit this, all that I can propose is
sequestering even more carbon obtained, one way or the other, from the
atmosphere. So possibly it is necessary to sequester 500 GtC, or
possibly even more, to counteract the warming effects of atmospheric
methane.
Regarding damages to ecosystem support, I suggest you consider the
oceans: both temperature and CO2 are important to the health of the
oceans; both are too high right now.
I hope this is some some small benefit. Please feel free to ask
questions. Thre are several regulars here who I am sure will be
pleased to help.
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