Carbon Dioxide and Earth's Future Pursuing the ... - Magazooms

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On the basis of these observations, which apply to the entire Arctic, it is not possible to assess
the influence of atmospheric CO2 on surface air temperature within this region, or even
conclude that it has any effect at all. Why? Because over the first 115 years of warming, as the
air’s CO2 concentration rose by an average of 0.24 ppm/year, the air temperature rose by an
average of 0.013°C/year; while over the final 35 years of the record, when the increase in the
air’s CO2 content really began to accelerate, rising at a mean rate of 1.17 ppm/year (nearly five
times the rate at which it had risen in the prior period), the rate of rise of surface air
temperature did not accelerate anywhere near that fast. In fact, it did not accelerate at all. In
fact, it decelerated, to a mean rate of change (0.011°C/year) that was nearly the same as the
rate at which it had previously risen but in the opposite direction, i.e., downward. Clearly, there
was something that totally overpowered whatever effect the rise in the air’s CO2 content over
the first period may, or may not, have had on the temperature of the Arctic, as well as the
effect of the nearly five times greater rate of rise in the air’s CO2 content over the second
period.
Concentrating wholly on directly-measured temperatures, as opposed to the reconstructed
temperatures derived by the proxy approach of Overpeck et al. (1997), Polyakov et al. (2003)
derived a surface air temperature history that stretched from 1875 to 2000 based on data
obtained at 75 land stations and a number of drifting buoys located poleward of 62°N latitude.
This effort allowed the team of eight U.S. and Russian scientists to determine that from 1875 to
about 1917, the surface air temperature of the huge northern region rose hardly at all; but then
it took off like a rocket, climbing 1.7°C in just 20 years to reach a peak in 1937 that has yet to be
eclipsed. During this 20-year period of rapidly rising air temperature, the atmosphere’s CO2
concentration rose by a mere 8 ppm. But then, over the next six decades, when the air’s CO2
content rose by approximately 55 ppm, or nearly seven times more than it did throughout the
20-year period of dramatic warming that preceded it, the surface air temperature of the region
poleward of 62°N experienced no net warming and, in fact, may have actually cooled a bit.
In light of these results, it is difficult to claim much about the strength of the warming power of
the approximate 75-ppm increase in the atmosphere’s CO2 concentration that occurred from
1875 to 2000, other than to say it was miniscule compared to whatever other forcing factor, or
combination of forcing factors, was concurrently having its way with the climate of the Arctic.
One cannot, for example, claim that any of the 1917 to 1937 warming was due to the 8-ppm
increase in CO2 that accompanied it, even if augmented by the 12-ppm increase that occurred
between 1875 and 1917; for the subsequent and much larger 55-ppm increase in CO2 led to no
net warming over the remainder of the record, which suggests that just a partial relaxation of
the forces that totally overwhelmed the warming influence of the CO2 increase experienced
between 1937 and 2000 would have been sufficient to account for the temperature increase
that occurred between 1917 and 1937. And understood in this light, the air’s CO2 content does
not even begin to enter the picture.
But what about earth’s other polar region: the Antarctic? Here, too, one can conclude nothing
about the influence of atmospheric CO2 on surface air temperature. Why? Because for the
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