Re: [geo] Re: Rejected - a simple argument for SRM geoengineering AND did you
get that right?From Lenton and Vaughn (2009):
"First we consider the calculation of effects on atmospheric
CO2 (deltaCatm) over time. Adding CO2 to the atmosphere or
removing CO2 from the atmosphere triggers responses from
the ocean and land reservoirs that are continuously exchanging
CO2 with the atmosphere. The result is that any perturbation
to atmospheric CO2, whether an increase or a decrease,
decays over time towards around 20% of its original size on
a millennial timescale. The fraction of the original perturbation
remaining after a given time, deltat (in years), is called the
airborne fraction, f (deltat). It is a complex function containing
multiple decay timescales, related to multiple land and ocean
carbon reservoirs. For relatively small perturbations, it can
be approximated, from the Bern carbon cycle model (Joos et
al., 1996) by:
f (deltat)=0.18+0.14e-deltat/420+0.18e-deltat/70
+0.24e-deltat/21+0.26e-deltat/3.4 (15)
According to this formula, for an instantaneous removal
of carbon from (or release to) the atmosphere, 92% is still removed
(or present) after 1 year, 64% after 10 years, 34% after
100 years, and 19% after 1000 years. This is a little confusing
when compared with observations over 1960-2007 that
the increase in atmospheric CO2 in a given year was only
~50% of the total emissions that year. The discrepancy can
be explained by the fact that in any given year, the natural
land and ocean carbon sinks represent an integrated response
to all previous years of emissions."
So as noted in my draft presentation from a week ago, CO2 emitted today has a
variable lifetime and this must be considered in assigning which CO2 is removed
from the atmosphere and by what process. Considering CO2 emitted this year,
one can think of it as somewhat like a warehouse where all of the inventory
arrives at the same time, but is sold and leaves the warehouse at different
rates, the last 20% taking more than 1000 years. And it's not Copenhagen,
it's Copouthaven.
----- Original Message -----
From: Mike MacCracken
To: Peter Read ; Martin Hoffert ; David Keith ; Greg Rau ; Geoengineering ;
John Nissen ; Ron Larson ; David Hawkins
Sent: Saturday, November 21, 2009 8:56 AM
Subject: Re: [geo] Re: Rejected - a simple argument for SRM geoengineering
AND did you get that right?
Hi Peter--Problem with your analysis is that biosphere also gives off
something like 60 GtC as well. Preindustrial with steady CO2, as much was being
taken up and given off. The net uptake, driven by the gradient created by
emissions is now something like 1 GtC/yr and would equilibrate well before all
of the perturbation is removed for this net uptake is occurring mainly as the
new emissions are distributed among the fast reservoirs (atmosphere something
like 50%, upper ocean that is well mixed 20-25% (and this includes the maybe 1
GtC/yr or less headed to the deep ocean), and terrestrial biosphere something
like 25-30%. My upper ocean and terrestrial biosphere numbers may be off a bit,
but close.
You are counting the gross flux--sort of like saying how much cash is going
into the stock market by only counting the dollars used to buy the stocks
without subtracting off the money coming out due to sales.
Mike
On 11/21/09 3:20 AM, "Peter Read" <pre...@attglobal.net> wrote:
I must be off the map somewhere I guess, but in my view you guys have got
it wrong
This is because the calculations pertain exclusively to atmospheric
physics/chemistry.
In fact the biosphere fixes about 60 Gt C annually plus another 20
including oceanic photosynthesis
So with less than 800 GT in the atmosphere, incremental CO2 stays in the
atmosphere for around 10 years, not 10,000
Of course, if natural and anthropogenic fixation is exactly balanced by
decay for 10,000 years then the physical-chemical processes are all that
matters. But is that likely?? An increment of CO2 will cause an increment of
CO2 fertilization, allowing for which would lead to a smaller lifetime I
suspect [can anyone do the sum please?]. But an increment of CO2 will cause
incremental warming and incrementally hasten decay, possibly lengthening the
10,000 years .
However, I am much more concerned with the presentational aspect of the
10,000 years number. This lends credence to the overwhelming importance of
reducing emissions [[unless, that is, you happen to think that shorter term
climatic impacts, like the risk of Greenland collapsing, are important]].
I believe the science should be stated in a way that emphasizes the carbon
cyle as a whole, and the ease of getting CO2 out of the atmosphere, not the
very difficult (costly) problem of stopping it being emitted.
Peter
----- Original Message -----
From: Marty Hoffert <mailto:marty.hoff...@nyu.edu>
To: ke...@ucalgary.ca ; r...@llnl.gov ; mmacc...@comcast.net ;
geoengineering@googlegroups.com
Sent: Saturday, November 21, 2009 12:00 PM
Subject: RE: [geo] Re: Rejected - a simple argument for SRM
geoengineering
David et al:
True, Jim Kasting's work on the long-term carbon cycle as impacted by
human fossil fuel CO2 emissions is decades old. But brilliant though Jim is,
he was not the first. See, e.g., the attached paper published in 1974 when it
first dawned on me and others at NASA/GISS that we might be on to something
important with the fossil fuel O2 greenhouse-climate issue. Who would have
thought that Steve Schneider, Richard Sommerville, Jim Hansen and yours truly
would be pounding the table in 2009 for the world to act to limit emissions?
(Remember, the planetary climate was still cooling in the '70s.) My '74 Atmos
Env. paper admittedly has (minor in the overall scheme of things) errors. Not
too surprising for an early probes into the far horizons of humankind's
future. (Still, Dave Keeling liked it.) Finding those conceptual errors might
be fun exercise for a carbon cycle savvy reader 35 years later.
But mostly, I think, I was right about the longevity of the impacts of
the fuel era of human history through persistent elevated CO2 levels. Nobody
much listened at the time and the paper was buried in in the resting place of
specialized academic journals, though I was able to resurrect it with the help
of the Internet.
But Hey: Is anyone listening now? Will they care in Copenhagen?
Cheers,
Marty Hoffert
Professor Emeritus of Physics
Andre and Bella Meyer Hall of Physics
4 Washington Place
New York University
New York, NY 10003-6621
---
----- Original Message -----
From: Ken Caldeira <mailto:kcalde...@stanford.edu>
To: Ron Larson <mailto:rongretlar...@comcast.net>
Cc: dhawk...@nrdc.org ; geoengineering@googlegroups.com
Sent: Friday, November 20, 2009 2:08 PM
Subject: Re: [geo] you got that right
1 digit calculations just for orders of magnitude:
If we assume a doubling of CO2 is 4 W / m2 and the earth is 5 x 10^14
m2, a doubling of CO2 traps about 2 x 10^15 W.
If we assume 2 GtC / ppm, and think it takes say 300 ppm to double CO2,
that is 600 GtC, 600 x 10^12 kgC = 6 * 10^14 GC, so each kgC in the atmosphere
traps around 3 W.
Oil is about 4.5 x 10^7 J / kg. If we pretend oil is CH2, then we can
assume that most of this mass is carbon, but a lot of the energy comes for the
hydrogen. So by this reckoning it would take ( 4.5 x 10^7 J / kg ) / (3 W /
kgC) = 1.5 * 10^7 s or less than half a year for the greenhouse gas to heat up
as much as the thermal heating from the oil.
Of course, this CO2 is accumulating in the atmosphere.
If you think the airborne fraction on the margin, is around 0.5 over the
first thousand years, giving you about the radiative heating each year
equivalent to the chemical heating from burning. Then you get a few hundred
thousand years with several fold less heating, with a cumulative radiative
heating on the order of 100,000 times the direct chemical heating. (I am not
going to quibble about small integer multipliers one way or the other.)
Of course, all of this heat will not go into melting ice.
(I think that 75 was the ratio of current atmospheric CO2 radiative
forcing to direct heating from fossil fuel burning, but I would need to go
back to check.)
___________________________________________________
Ken Caldeira
Carnegie Institution Dept of Global Ecology
260 Panama Street, Stanford, CA 94305 USA
kcalde...@ciw.edu; kcalde...@stanford.edu
http://dge.stanford.edu/DGE/CIWDGE/labs/caldeiralab
+1 650 704 7212; fax: +1 650 462 5968
On Thu, Nov 19, 2009 at 3:08 PM, Ron Larson <rongretlar...@comcast.net>
wrote:
Dave (cc Ken and list):
Thanks to Dave.
1. Since I doubt very much that the computation shown included
anything on CO2 effects, I hope Ken can weigh in on this, per the discussion
last week re:
http://climateprogress.org/wp-content/uploads/2009/11/Warming-burning-091018.pdf
2. The answer might be 100,000 times larger - but that might
exhaust the supply of glaciers.
3. Would Exxon today say that one day's worth of melting was
calculated properly. That we are only talking of an insignificant addition of
only about 75/365 (only about another 20%, assuming we don't worry about
whether today's energy consumption is impacting any glacier tomorrow.) (Ken
had a factor of 75 for 1 year).
4. I haven't had any luck logging on to to leave a comment at
the Grist site, so hope someone will. One chap has shown a multiplicative
factor of 65 - which looks like he has calculated for a year.
Ron
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