I was disappointed to read Leonard Teschler's Datum column, entitled "Greenhouse gas or just hot air?", (MD Aug 9, 2007) in which  Mr. Teschler gives an example of "innumeracy", or lack of fluency with numbers.  Unfortunately, the example he sited may inadvertently portray an innumeracy of Mr. Teschler. 

Mr. Teschler critiques the following quote from an environmental engineering professor: "Thirty percent of carbon dioxide emitted into the atmosphere originates from fossil-fuel-fired power plants."  Mr. Teschler claims that statement to be false on the face of it, siting Wikipedia, "....the sum total of all man-made carbon-dioxide emissions account for only about 5% of the CO2 in the atmosphere."   (The emphasis on into and in is mine). 

What is being compared, however, is the rate of CO2 entering the atmosphere, continuously, with a static amount, or snapshot, of CO2 resulting from man-made emissions -- apples and oranges.   Now, can the two figures mentioned be mathematically consistent?  Yes.  The atmospheric CO2 from natural sources (95% as per Wikipedia) accumulated over perhaps a billion or so years.  If in the 8000 years of civilized mankind, and mostly in the last few hundred years, man-made CO2 has accumulated to 5% of the total atmospheric CO2, that would be perfectly plausible and numerologically correct.... It would also be very alarming. 

I agree with Mr. Teschler when he suggests not getting "locked into name calling and acrimonious CO2 debates."   Nevertheless, I cannot understand what he means by the term "radical environmentalist."  Are there just "environmentalists" also, and what is the difference?  I don't claim to be a climatologist, and I don't believe Mr. Teschler does either.  Preconceptions abound on both sides of this question.   I prefer to read the facts and keep an open mind, perhaps with a bias to caution.  It certainly conserves fossil fuel foreign trade deficits.

Or, is this just a trick article to see if any engineering "numerologists" are paying attention?

Rshaper:

 

Mr. Teschler got the underlying fact correct: mankind's contribution to the annual production of CO2 is roughly 3.5-5%. Hundreds of gigatons of CO2 are pumped into the atmosphere by natural sources, and they account for the remaining 95% or so. Check: http://www.radix.net/~bobg/faqs/scq.CO2rise.html

Stephen,

Very interesting link you provided.  .  The issue with Mr. Teschler's article was with mixing up rate of contribution of CO2 with amount of CO2 at a point in time.  Getting a "correct" answer via erroneous means often leads to erroneous conclusions, as many an engineer has learned the hard way.

 Nevertheless,  Mr. Teschler did not get it correct.  According to the analysys in the link you provided, the CO2 rise from 280 to 358 ppmv (from 1800 to 1994) is attributed to human origin, making the human proportion of CO2 today over 20%. 

Below are the opening paragraph and some salient points

Time and again, some people claim that human activities are only
a minor source of atmospheric carbon dioxide (CO2) which is swamped
by natural sources.  Compared to natural sources, our contribution is
small indeed.  Yet, the seemingly small human-made or `anthropogenic'
input is enough to disturb the delicate balance.   "Anthropogenic CO2
is a biogeochemical perturbation of truly geologic proportions"
[Sundquist] and has caused a steep rise of atmospheric CO2.

From its preindustrial level of about 280 ppmv (parts per million
by volume) around the year 1800, atmospheric carbon dioxide rose to
315 ppmv in 1958 and to about 358 ppmv in 1994  [Battle] [C.Keeling]
[Schimel 94, p 43-44].   All the signs are that the CO2 rise is
human-made:

*  Ice cores show that during the past 1000 years until about the year
   1800, atmospheric CO2 was fairly stable at levels between 270 and
   290 ppmv.  The 1994 value of 358 ppmv is higher than any CO2 level
   observed over the past 220,000 years.  In the Vostok and Byrd ice
   cores, CO2 does not exceed 300 ppmv.  A more detailed record from
   peat suggests a temporary peak of ~315 ppmv about 4,700 years ago,
   but this needs further confirmation. [Figge, figure 3] [Schimel 94,
   p 44-45] [White]

*  The rise of atmospheric CO2 closely parallels the emissions history
   from fossil fuels and land use changes [Schimel 94, p 46-47].

*  The rise of airborne CO2 falls short of the human-made CO2 emissions.
   Taken together, the ocean and the terrestrial vegetation and soils
   must currently be a net sink of CO2 rather than a source [Melillo,
   p 454] [Schimel 94, p 47, 55] [Schimel 95, p 79] [Siegenthaler].

*  Most "new" CO2 comes from the Northern Hemisphere.  Measurements
   in Antarctica show that Southern Hemisphere CO2 level lags behind
   by 1 to 2 years, which reflects the interhemispheric mixing time.
   The ppmv-amount of the lag at a given time has increased according
   to increasing anthropogenic CO2 emissions. [Schimel 94, p 43]
   [Siegenthaler]

*  Fossil fuels contain practically no carbon 14 (14C) and less carbon
   13 (13C) than air.  CO2 coming from fossil fuels should show up in
   the trends of 13C and 14C.  Indeed, the observed isotopic trends
   fit CO2 emissions from fossil fuels.  The trends are not compatible
   with a dominant CO2 source in the terrestrial biosphere or in the
   ocean.