AGW and CO2: Are humans responsible for the increase in CO2?
by Anthony Cox
==========================
The empirical evidence for an increase in atmospheric CO2
over the 20thC is fairly uncontroversial. The increase in CO2 levels began
about 1850 when the
Little
Ice Age ended. The acceleration in CO2 levels began about 1900 when they
were 280 parts per million [ppm] and have continued until they are now
394 ppm.
Until the 20thC records of atmospheric CO2 levels show a
basically constant CO2 with variation as little as 10ppm over centuries. These
past records are based on
ice cores.
The theory is that natural emissions of CO2 and sinks, or places where the CO2
is absorbed, were in equilibrium. This all changed when human emissions of CO2,
ACO2, began.
The official viewpoint about why CO2 levels have increased
over the 20thC is put forward by the
EPA.
The EPA makes a comparison with a bath-tub. They say prior to the increase in
ACO2, natural emissions of CO2 were like water from the “spigot” going into the
bath-tub and natural sinks were like the drain. The level of CO2 never changed
because nature, like the bath-tub, was in balance. ACO2 upset this balance by
being like a glass of water which was poured into the bath-tub and is
responsible for the increase in CO2.
There are a number of problems with this official view. The
first is the assumption that past CO2 levels were as unvarying as the ice cores
suggest. The problems with the ice cores is they are subject to
close-off fractionation, or leakage of gases from the gas
trapped in the ice, because of ice pressure; this process is related to the
kinetic diameter of the gas molecules not the collision diameter; something
which confuses even experts who gave ice cores a clean bill of health as a
proxy for past CO2 levels.
The result
of close-off fractionation is that ice cores may underestimate past levels and
fluctuations of atmospheric CO2, as Drake, Jaworowsky, Glassman and Segalstad have proposed.
Arguably
the most reliable history of past CO2 levels is from plant stomata records as Figure 12 shows. Figure 12
indicates past levels of CO2 were almost at today’s levels as recently as 1550.
In addition chemical analyses of CO2 levels in Figure 13 show CO2 levels
higher than today in the early 1800’s.
If the stomata and chemical analysis records are right this
would mean that the natural emissions and sinks, the spigot and drain of the
system are not always in equilibrium. In turn this would throw doubt on the
assumption that there was equilibrium between natural emissions and sinks at
the beginning of the 20thC before ACO2 allegedly caused the increase in CO2.
Further doubt on this assumption of a natural equilibrium is
contained in 2 recent papers.
The first is by
Tom
Quirk. Figure 1A from Quirk shows the ACO2 emissions with the increase in
atmospheric CO2:
If the assumption about the equilibrium between natural
emissions and CO2 and sinks was correct the increase in atmospheric CO2 would
correlate with the ACO2 emissions since, according to the EPA, the increase in
the CO2 is entirely due to that extra glass of ACO2 being added to the
’bath-tub’ or atmosphere. However there is no such correlation; and since we
know what the ACO2 emissions are the lack of correlation between ACO2 and the
increase in CO2 must mean there is no equilibrium between the natural emissions
and sinks.
Quirk also shows the natural CO2 emissions and sinks are
strongly correlated with changes in ENSO, the pattern of El Nino and La Nina
episodes. There have been
stronger
warm ENSO periods since the LIA. Warmer ENSO periods would lead to higher
sea surface temperatures. According to
Henrys Law with warmer sea
surface temperatures more natural CO2 would be emitted from the oceans into the
atmosphere. This is one possible reason why natural CO2 has been contributing
to the increase in atmospheric CO2.
Knorr found the airborne fraction [AF] of ACO2 has not changed in 150
years. The AF is the % of ACO2 emissions which remain in the atmosphere
contributing to the increase in atmospheric CO2 levels. The constant AF found
by Knorr was about 40%.
Figure 1 from Knorr illustrates this:
Knorr describes Figure 1 as “Observed atmospheric CO2 increase derived from
direct measurements, taking the average of Mauna Loa (Hawaii) and the South
Pole (thin solid line), and two ice cores: Law Dome (dashed thin line) and
Siple (dotted thin line). This is compared to total anthropogenic emissions
(thick solid line) and 46% of total emissions (thick dashed line)”.
The 46% in fact was an estimate by Dr
Knorr [as indicated in private correspondence] and should be 40% as the calculated
amount of the constant AF. The graph shows that general atmospheric CO2 is
increasing by much less than the amount of the ACO2 emissions. It is this which
underpins the argument that ACO2 is responsible for all the increase in
atmospheric CO2. That is, given the assumption that natural emissions and sinks
were in equilibrium before ACO2 started to increase, the official position is
now that the sinks have increased to absorb some of the increase in ACO2 but
not all and that remainder of non-absorbed ACO2 is what is causing the increase
in atmospheric CO2.
Quirk and the stomata history has
already shown that the assumption that natural CO2 emissions and sinks were in
equilibrium is problematic. What the constant AF shows is that the increase in
ACO2 and natural sinks does not explain the increase in atmospheric CO2. The AF
does this because it is the ONLY amount of ACO2 available to increase the
atmospheric CO2. The expanding sinks are absorbing about 60% of the increase in
ACO2 but as Knorr’s figure 1 plainly shows atmospheric CO2 increase is
expanding more than the remaining 40% of ACO2 left. This is shown by all the
peaks above the thick dashed line. If the AF were graphed at its correct 40% it
would be slightly lower than shown in Knorr’s graph. This is plainly shown in
this graph based on the Mauna Loa measurements from 1959:
Graph by Ian Hill
Clearly the AF is predominantly below
the yearly increase in atmospheric CO2. This is reflected in a comparison
between the slopes of the increase atmospheric CO2 which is 0.0575 and the AF
which is 40% of the increase in ACO2, or 0.0447. That is, the AF is increasing LESS
than the increase in atmospheric CO2. Even in those years when the increase
falls below the AF it cannot be said that natural CO2 emissions are not
contributing because of the lack of equilibrium between CO2 emissions and
sinks.
The effect can be compared with the principle of a
constant in an increasing total: say ACO2 is 40% of all CO2 [as per the
constant ACO2 AF] which is 100, so ACO2 is 40 and natural CO2 is 60; when all
CO2 is 200 ACO2′s 40% will be 80 so natural CO2 will be 120, an increase of 60;
at 300, ACO2 is 120, natural CO2 is 180 and so on; natural CO2 MUST be
contributing to the increase in total CO2.
Man made global warming [AGW] is based on human emissions of CO2
disrupting the climate. The basic science supporting AGW has been shown to be defective. If it
turns out that human emissions of CO2 are not the primary reason for the
increase in atmospheric CO2 then even further doubt is cast on the theory of
AGW.
