[asa] A Response to the BBC Documentary on The Great Warming Swindle-4

4. The documentary claims that much of the warming in the 20th century
occurred in the first half of the century before CO2 levels had risen much and
that there was actually a cooling period from 1940 to 1980 just when carbon
dioxide emissions were really beginning to ratchet upwards.
Response: Once again the facts here are substantially true although the graph
they depict for temperature change in the 20th century appears to have been
altered somewhat to favor their argument. For a better graph see
http://en.wikipedia.org/wiki/Image:Instrumental_Temperature_Record.png
And the documentary does not point out that there are some plausible
suggestions for the decline and leveling off of temperature during the four
decade period beginning in 1940. This was the time of the second world war; it
was a time also of great industrial growth in the West - the smokestack era; it
was the time of the atmospheric testing and use of nuclear weapons; it was a
time when there was little or no regulation of atmospheric emissions the Clean
Air Act did not arise until 1963; it was a time when CO2 levels began rising
more quickly but also levels of other pollutants - especially dust,
micro-particulates and aerosols - especially those caused by sulfate emissions
(acid rain) due to coal combustion. All of these latter atmospheric polluters
would have the effect of cooling that earth because these materials scatter
sunlight and less solar radiation is absorbed by the earth. It is at least
plausible to suggest that the warming one might expect that would occur from
rising CO2 levels was offset by the rising levels of these other pollutants.
Then after serious efforts to address these other forms of atmospheric
pollution began in the mid 1960s, the warming due to atmospheric carbon dioxide
began to become observable. The cooling effect of atmospheric dust and aerosols
was confirmed by the volcanic eruption of Mt. Pinitubo in 1992 which emitted
large amounts of particulates and sulfur dioxide high into the atmosphere -
even the stratosphere resulting in an observable cooling for the next two
years.

Ken Piers

"We are by nature creatures of faith, as perhaps all creatures are; we live by
counting on things that cannot be proved. As creatures of faith, we must choose
either to be religious or superstitious, to believe in things that cannot be
proved or to believe in things that can be disproved."
Wendell Berry

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Received on Wed Mar 21 11:37:17 2007