From: SCHLOERER@rzmain.rz.uni-ulm.de (Jan Schloerer)
Subject: Re: Gallup Poll on Global Warming
Organization: University of Ulm, Germany
Date: Tue, 15 Sep 1992 20:04:11 GMT
X-News-Reader: VMS NEWS 1.24

In   <1992Sep12.135349.20578@news.acns.nwu.edu>
     len@schur.math.nwu.edu (Len Evens)    wrote

> ...  I was under the impression that the theoretical expectation
> that CO_2 levels should rise with increased burning of fossil fuels
> has in fact been verified by observational data.  I also seem to
> remember that the levels have not risen as fast as might be
> expected so that the sinks are not entirely understood.  However,
> I thought that plausible models suggest that without stabilization
> of the use of fossil fuels, there will be something like a doubling
> of CO_2 levels within about 50 years.  ...
> Would someone please comment on this issue ?  ...


The following will not answer all your questions  (I'm not competent
for that, moreover some of your questions have been discussed in recent
posts by others in this thread).  But perhaps it helps a bit ...

The recent figures are  [IPCC 1992, p8-9, 13, 31-35] :

    Global fossil fuel emissions 1987                   5.7 +- 0.5 GtC
    Global fossil fuel emissions 1989 and 1990          6.0 +- 0.5 GtC
    Annual average net flux from land-use changes
      (primarily deforestation) during the 1980s        1.6 +- 1.0 GtC

    Fraction of the CO2 emissions which remains
       in the atmosphere (for the last decade)         46   +- 7   %

    Estimate for the annual ocean uptake                2.0 +- 0.8 GtC
       There has been some work indicating that
       the ocean sink may only be of the order of
       1 GtC/year.  However, most work seems to
       favour a somewhat larger oceanic sink.
       Short overviews:               IPCC 1992 ,  33- 34
       Richard Kerr, Science 256 ( 3 April 1992),  35
       Andrew Watson, Nature 356 (16 April 1992), 561-562
              
    Imbalance = "missing sink"            of order of   1 - 2  GtC/year
       If one assumes that the missing sink is in the
       vegetation, there remain several options, e.g.,
       CO2 fertilization,  N fertilization,  forest
       regrowth in temperate latitudes.  None of these
       can presently be quantified.

1 GtC (gigatonne of carbon) equals one billion (10^9) tonnes of carbon.
About 3.7 Gt CO2 correspond to 1GtC. Please don't ask me for the meaning
of the +- , they don't explain it.  To me, it looks like "informed esti-
mates", i.e., the quantity is "unlikely" to lie outside the respective
range, e.g., 39-53 % for the fraction of CO2 remaining airborne.  Might
also be standard deviation or some such, but this would perhaps have
been mentioned.

"For a given emissions scenario, the differences in predicted changes
in CO2 concentrations, neglecting biospheric feedbacks, are up to 30%,
but this is unlikely to represent the major uncertainty in the prediction
of future climate change compared to uncertainties in estimating future
patterns of trace gas emissions, and in quantifying physical climate
feedback processes.  Future atmospheric CO2 concentrations resulting
from given emissions scenarios may be estimated by assuming that the
same fraction remained airborne as has been observed during the last
decade, i.e., 46 +- 7% ."  [IPCC 1992, p35]

The  "CO2 fertilization feedback"  included in the calculations of
Wigley & Raper  [Implications for climate and sea level of revised IPCC
emissions scenarios, Nature 357, 28 May 1992, 293-300]  is presently
just a term to account for the missing sink.  It does not tell which
of the potential mechanisms (CO2 fertilization, N fertilization, forest
regrowth, or others) contributes how much to the sink.  Wigley & Raper
favour CO2 fertilization as the main factor involved in explaining the
missing sink.  The 16 authors and contributors to the IPCC 1992 section
"Greenhouse gases: sources and sinks"  are more neutral.

To round this off, I include (once again, sorry :-)  annual average
atmospheric CO2 concentrations for the Northern Hemisphere in parts per
million by volume (ppmv), from the Mauna Loa Observatory at Hawaii [1].
Plus signs (+) denote El Nino warming events, the peak warming usually
occurs late in the given year and extends into the first months of the
next year [IPPC 1990, p227]. Several explanations have been proposed for
the "CO2 jumps" after El Ninos:  the warm water may contain less nutri-
ents, so bioproductivity may be reduced [2, p33-34]  /  CO2 outgassing
from the warm water  /  processes in the land biosphere, perhaps in
response to climatic events connected with El Nino. In 1990, the books
on the matter were not closed [IPCC 1990, p14].  Another confounding
factor:  some El Nino warming events, such as 1987/8, are strong, while
others are weak, e.g. 1976/77.  So, instead at individual years, you'd
rather take a look at the, say, 10 years-average increase of CO2.

  Year    ppmv CO2          Year    ppmv CO2          Year    ppmv CO2

  1959      315.83         
  1960      316.75           
  1961      317.49          1971      326.16          1981      339.76
  1962      318.30          1972 +    327.29          1982      340.96
  1963 +    318.83          1973      329.51          1983 +    342.61
  1964     (missing)        1974      330.08          1984      344.25
  1965 +    319.87          1975      330.99          1985      345.73
  1966      321.21          1976 +    331.98          1986      346.99
  1967      322.02          1977      333.73          1987 +    348.79
  1968      322.83          1978      335.34          1988      351.35
  1969 +    323.93          1979      336.68          1989      352.75
  1970      325.27          1980      338.52          1990      353.95

[IPCC 1990]   Climate Change  -  The IPCC Scientific Assessment
    Cambridge Univ. Press, Cambridge, UK 1990
[IPCC 1992]   Climate Change 1992
    The Supplementary Report to the IPCC Scientific Assessment
    Cambridge Univ. Press, Cambridge, UK 1992
[1] CO2 data:  C.D.Keeling,  Scripps Institution of Oceanography,
    Univ. of California, La Jolla, CA 92093,  obtained from CDIAC's
    ftp-archive,  cdiac.esd.ornl.gov [128.219.24.36],  April 1992.
    There you can also get the CO2-data from Antarctica, they show a
    lag of about two years, but otherwise the levels are the same.
[2] Hermann Flohn, Das Problem der Klimaaenderungen in Vergangenheit
    und Zukunft.  Wissenschaftliche Buchgesellschaft, Darmstadt,
    Germany 1985


Jan Schloerer          schloerer@rzmain.rz.uni-ulm.de
Klinische Dokumentation           Uni Ulm
Postfach 3880     DW-7900 Ulm     Germany
Newsgroups: sci.environment