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GtC and GtCO2 in AR5 (fwd)
(two numbers written wrongly in my original letter
have been corrected in the copy below;
two highly respected experts on metrology have principially endorsed
my beg after prof. Stocker did not follow it
---------- Forwarded message ----------
Date: Sun, 12 Jan 2014 22:54:19 +0100 (CET)
From: Jan Hollan <hollan@mail....cz>
Cc: owm@nist..., martin.milton@bipm..., i.m.mills@reading....uk,
Subject: GtC and GtCO2 in AR5
Dear Professor Stocker,
I have a big beg, considering you to be the last instance as the main
author of WG I report.
The IPCC documents depart in several ways from the rules for proper
communication of quantities as demanded by BIPM and NIST. I wrote about
that to various "TSUs" in time of AR4 already. At least the most painful
departure should be corrected:
mixing a unit with a chemical symbol, namely
"GtC" and "GtCO2"
Esp. expressions like (first line on p. 10 of SPM):
"Annual CO2 emissions from fossil fuel combustion and cement production
were 8.3 [7.6 to 9.0] GtC yr-1"
are monsters, IMHO.
I'm sending my beg to the selected addresses of BIPM an NIST in CC too,
hoping they might support my position. IPCC makes the greatest
scientific assessments since decades, and if it uses an inferior
language, it poisons the whole communication of science to the mankind,
and the efforts of BIPM and NIST go to vain. As do the efforts of those
(incl. me) who nurture didactics of physics.
In my humble view (as a senior educator in astronomy and environmental
physics), it's so evident, that no further arguments should be needed.
But maybe it is not so evident to many honorable physicists and
scientists including you. So I dare to add the basic reasoning below, I
apologize that it is not quite short.
May I be so offensive to ask you, if you would consider to rectify at
least this departure from proper scientific language in WG I part of
AR5? Or if you would publish an open letter to me (as my letter is open
too), in which you would defend your position of ignoring BIPM and NIST
A simple cure of the above "sin", placing a space between a symbol of
unit and a chemical symbol (Gt C), is not enough there, as NIST stresses
"7.5 Unacceptability of mixing information with units"
"the Pb content is 5 ng/L but not: 5 ng Pb/L or 5 ng of lead/L"
Expressing C and CO2 amounts transparently is a serious matter. It is
not difficult at all. The sentence from SPM could read:
"Annual carbon emissions from fossil fuel combustion and cement
production were 8.3 [7.6 to 9.0] Gt yr-1"
with a footnote 12 saying not
"1 Gigatonne of carbon = 1 GtC = 10^15 grams of carbon. This corresponds
to 3.667 GtCO2"
"1 Gt, one gigaton, is 10^9 t or 10^15 g (1 Pg, one petagram). 1 Gt of
carbon, when oxidized, results in 3.667 Gt of CO2."
Using a confusing, SI-ignoring jargon is common in some disciplines. But
papers and assessments presented to public should be cleaned of it.
Otherwise the public can say -- well, these experts did not even learn
the basic rules of quantitative language, how could we trust they
understand the very issue they are speaking about?
In my Czech translations and English writings, I always change
"CO2 emissions (GgC)"
"emissions of carbon / Gt".
(The 1/1000 of carbon which is not oxidized but emitted as black carbon,
can be neglected.)
My decade long experience says that measuring CO2 in strange "units"
"1 GtC" which equal 3.67 Gt
leads to complete confusion of even the most educated public. Even for
me it takes time to be certain whether the authors mean
1 Gt, 3.67 Gt or 1/3.67 Gt
in various texts and their parts. Many quotations from such texts get
AR5 is great for its SPM10 figure and exposing the carbon budget. It's a
pity the jargon style of expressing it damages its seriousnes. If a
student of a secondary school would use it in a physics course, it would
be a reason to reject his homework and demanding him to make it
compatible with the proper language of science.
As I mentioned already, I've demanded IPCC to behave according to the
standards earlier, a published letter which does not stress the GtC
nonsense at its very introduction is
It references the NIST documents I use from ancient times; now even the
analogous BIPM ones are at hand:
(sections 5.2.1 to 5.3.3 are relevant, then 5.3.7 saying a space must
be before a % symbol)
The same sections start at p. 39 of a file
or at p. 46 of
Jenik Hollan, editor of Czech versions of AR4 documents --
(and many other climate change related one, inc. the emerging AR5, see
ev. the first step in that, SPM figures
Jan Hollan, Ph.D.
Global Change Research Centre of the Acad. Sci. Czech Rep.
AdMaS - Advanced Materials, Structures and Technologies Centre
of the Brno University of Technology
Lipová 19, 602 00 Brno fix. +420 5 43 23 90 96
mob. +420 606 073 562
volunteer of the Ecological Institute Veronica
Panská 9, 602 00 Brno, Czechia http://www.veronica.cz