Re: [asa] Re: more CO2

From: James Mahaffy <>
Date: Sat Feb 03 2007 - 19:14:30 EST

George and others. While it is less percentage than terrestrial systems a significant amount of
photosynthesis also occurs in the ocean. So you can not forget the algae.

James Mahaffy ( Phone: 712 722-6279
498 4th Ave NE
Biology Department FAX : 712 722-1198
Dordt College, Sioux Center IA 51250-1697
>>> "George Murphy" <> 02/03/07 4:29 PM >>>
Joel -

Thanks. I had received a couple of helpful off-list responses. There's one
thing I'm still not clear on. What I was thinking of when I posted my query
what I was thinking of was (1) decreased ability to take CO2 out of the
atmosphere by photosynthesis due to elimination of vegetation. When
reference is to "emissions associated with land use change" (as below), it
sounds like something different - namely (2) burning of vegetation &
consequent putting of CO2 into the atmosphere. The total effect of
deforestation would be additional CO2 emissions _plus_ decreased capacity
for removing CO2 in the future. Does the 20% figure include both effects,
or just (2)? & if the latter, how significant is (1)?

----- Original Message -----
From: "Joel Moore" <>
To: <>; <>
Sent: Saturday, February 03, 2007 2:24 PM
Subject: Re: more CO2


I didn't see any responses to your question about the effects of
deforestation on CO2. Deforestation was responsible for about 20% of
the rise on CO2 during the 1990s according to the current best
estimate in the most recent IPCC summary for policymakers. Here are
the relevant sentences from that summary:

"The primary source of the increased atmospheric concentration of
carbon dioxide since the pre-industrial
period results from fossil fuel use, with land use change providing
another significant but smaller
contribution. Annual fossil carbon dioxide emissions4 increased from
an average of 6.4 [6.0 to 6.8] * GtC (23.5 [22.0 to 25.0] GtCO2) per
year in the 1990s, to 7.2 [6.9 to 7.5] GtC (26.4 [25.3 to 27.5]
GtCO2) per
year in 2000–2005 (2004 and 2005 data are interim estimates). Carbon
dioxide emissions associated with
land-use change are estimated to be 1.6 [0.5 to 2.7] GtC (5.9 [1.8 to
9.9] GtCO2) per year over the 1990s,
although these estimates have a large uncertainty. {2.3, 7.3} "

*"In general, uncertainty ranges for results given in this Summary
for Policymakers are 90% uncertainty intervals unless stated
otherwise, i.e., there is an
estimated 5% likelihood that the value could be above the range given
in square brackets and 5% likelihood that the value could be below
that range. Best
estimates are given where available. Assessed uncertainty intervals
are not always symmetric about the corresponding best estimate. Note
that a number of
uncertainty ranges in the Working Group I TAR corresponded to 2-sigma
(95%), often using expert judgement. "

You can download the summary at

Sorry about the late response. I'm not on the list-serv but read the
archives once or twice a week.


> From: George Murphy <>
> Date: Sun Jan 28 2007 - 17:32:02 EST
> I appreciate many of the recent posts on global warming. I write a column
> for Lutheran Partners, a journal for ELCA clergy, on issues of science
> and technology in ministry, & will probably do my next one on global
> warming. I've saved some of the recent posts & expect that they'll be
> helpful for that.
> One question. 15-20 years ago there was a lot of discussion about loss of
> rainforests, especially in the Amazon, & the contribution of this to
> shifting O2 - CO2 proportions in the atmosphere. How significant a
> contribution is this in comparison with use of fossil fuels & other
> contributions to greenhouse gases?
> Shalom
> George

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Received on Sat Feb 3 19:15:17 2007

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