The proportion of C in the form of atmospheric CO2 is >99%. The next 
most common gas is CH4, currently ~1.8 ppm, compared with CO2 at ~400 
ppm. After that, you have numerous stable HC gases in ppb and ppt and 
then the halocarbons. These latter three categories are much worse than 
CO2 as GHGs (CH4 is ~35x, rising to PFCs at >10,000x. The effect of 
methane and other less stable HCs is variable according to the OH 
radical concentration, which is also variable according to the weather 
(e.g., high in a tropical rainforest after an intense storm, low in the 
Arabian desert). This is why methane is often quoted as a range of 
20-50x worse than CO2.

Particulate carbon is negligible in its effect; if it does not 
precipitate out by gravity, it is usually rained out within a day or 
two. This is amply demonstrated by the "blue moon" effect. If there is a 
lot of particulate carbon at tropopausal levels, the moon acquires a 
blue tinge. This happens, well, once in a blue moon! In my 73 years I 
can recall having seen two. The really pronounced one was, I think, in 
1949, when the sun also turned blue, even rarer, a weird phenomenon. It 
was caused by a really massive forest fire in Canada and the smoke was 
caught in the jetstream and transported to North Britain in a couple of 
days. It lasted less than a day, which shows the particulate matter 
simply falls to earth.

CO2 levels do vary locally, even diurnally, but the figures that are 
used are the annual averages, so that seasonal and diurnal variations 
are discounted. The interesting thing is that the annual averages are 
constant to within ±5 ppm at every observatory in the world (including 
the Mauna Loa one you cite, which has been doing the most intensive CO2 
research since 1957) and that they all follow the same upward curve [see 
Keeling, Callendar, Machta, Broecker and others) at increases of ~1.5 
ppm/year. Kellogg and Schware predict we'll hit the 500 ppm level 
between 2015 and 2035 (the curve is non-linear) if we continue burning 
fossil fuels "business as usual".

I must disagree with Grubler, as there is no doubt that human activity 
accounts for most of the increase of CO2 levels from 280 ppm in 1800 to 
about 400 ppm today. This is a 43% increase which is far too much to be 
lost in empirical errors, especially when it ties in so closely to the 
tonnage of fossil fuels consumed, bearing in mind the natural carbon 
cycle. Even worse is the increase of CH4, from 800 ppb to ~1800 ppb, 
today, an increase of 225% due to increased areas of rice paddies, 
enteric fermentation, leaks from natural gas installations, deliberate 
biomass burning and landfills, despite reduced natural methane from 
wetlands (marsh drainage) and termites. The tragedy of this is that CO2 
is much preferable to CH4 and man's activities are increasingly 
converting the carbon in CO2 to CH4.

The numbers I quote in this message ARE derived with scientific 
certainty, except for the 500 ppm predictions which are an extrapolation 
of known data. Analysis of gases in air can be done with great 
precision. Where there may be a small margin of error is in the 
**effect** that these gases may have in the long term.

I don't really know why I waste my time arguing the toss with you. We 
all know that we cannot pump pollutants into any natural cyclic system 
without upsetting the equilibrium. We cannot cause ~7 Gt of additional C 
to be pumped into the air because of using fossil fuels, compounded by 
deforestation, each year, when the total global atmospheric C is only 
750 Gt today. We have been doing this for 150++ years and it is entirely 
likely that what man has added altogether in that time exceeds what was 
there in the first place, before the industrial revolution (of course, 
some of extra has been absorbed into the natural carbon cycle, in the 
meanwhile, but ~43% of today's total remains). If you cannot see this as 
fact, then your head must be buried in the sand, up to your groin.

Brian

Charles Dolci wrote:
> Thank you for so thoughtfully pointing out my oversight that 6.6 PgC is
> not the same as 6.6 PgC of CO2.  So if Carbon is not the same as carbon
> dioxide then just how much of the 6.6 PgC actually becomes carbon
> dioxide. Your calculation assumes that all of that carbon from
> industrial activity becomes CO2. Is that realistic? How much of that
> carbon is in the form of particulates and carbon compounds other than CO2?
> 
> What is most interesting about the study by Grubler is the admission
> that they really don't know how much CO2 is emitted. They have to
> guesstimate based on economic activity. On page 13 he describes how they
> calculate carbon emissions -
> "... emissions, i.e. the efficiency of energy use per unit of GDP
> (Energy/GDP) as well as the carbon intensity of energy used (carbon
> dioxide/Energy)."
> 
> This may delight mathematicians but is it a reliable way to measure the
> amount of  CO2 (not just carbon - which is what they seem to be
> measuring) emitted from human activity?
> 
> Moreover, Grubler states that "human alterations to the carbon cycle are
> comparatively small, are difficult to quantify and are hence subject to
> considerable uncertainties, especially for land use change carbon
> emissions." pg 2;
> 
> In fact, uncertainty seems to be the byword for this report.
> Page 2 - "This estimated net biospheric flux is the difference between
> estimates of a variety of carbon sources and sinks ... and is affected
> by high uncertainty margins."
> Page 5 - "Whereas bottom-up assessments thus continue to be the best way
> for estimating current and historical gross carbon emissions, it is not
> possible yet to accurately determine net biospheric emissions."
> Page 15- "Because the energy use data include the historically important
> non-commercial uses of traditional biofuels, the resulting energy use
> and energy intensities ... estimates are subject to a high degree of
> uncertainty; the values given here are represent a conservative lower
> bound estimate ..."
> 
> Emissions are on thing, atmospheric concentrations are another. Grubler
> states at page 2 "The inter-annual variations of measured atmospheric
> carbon dioxide concentrations (5.4 parts per million by volume (ppmv) in
> 1998 at Muana Loa, Hawaii ... clearly indicate the importance of
> seasonal vegetation cycles in biospheric carbon fluxes. The inter-annual
> variation of 5.4 ppmv corresponds to some 11PgC.  Compared to the size
> of annual fluxes that characterize the carbon cycle and its inter-annual
> variations, anthropogenic alterations to the carbon cycle are
> comparatively small and hence impossible to measure directly."
> 
> Your 15 billion tonnes per year is slightly more than the inter-annual
> variation.
> The point of all this is that man is not yet capable of measuring the
> anthropogenic carbon (or CO2) emissions, and their best guesses show
> that it is "comparatively small" compared to natural sources.
> 
> Let's not pretend that our numbers are derived with scientific certainty.
> 
> Chuck
> 

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