[asa] A Response to the BBC Documentary on The Great Warming Swindle-6

6. The documentary asserts that variability in solar activity can account
for the changes in the temperature record in the past and is responsible for
the rise in temperature we are observing in recent decades.
Response: Some convincing graphs of solar activity vs temperature up to 1980
are shown and they refer to work published in 1991 by E. Friis-Christensen and
K. Lassen (Science, 1991 (254), 698-700), but note that they do not speak to
these authors. This 1991 paper has since been amended (in 2000 Lassen and
another co-worker themselves amended the 1991 paper - for a story on this
amended report see http://news.bbc.co.uk/2/hi/science/nature/734983.stm.
Other corrections to the 1991 paper have also been suggested: Damon & Laut
“Pattern of Strange Errors Plagues Solar Activity and Terrestrial Climate
Data”, Eos,Vol. 85, No. 39, 28 September 2004.
A very recent paper in Nature on solar luminosity and the earth’s climate
has been published: P. Foukal, et.al., Nature, 443, Sept. 14, 161-166 (2006).
This paper discusses satellite measurement of solar output since 1978 (that is
the date when we first began to make direct measurements of solar irradiance by
way of satellites and these are the best we have). Sunspot activity on the sun
varies roughly over an 11 year cycle with output maxima in 1980, 1991, and
2002. In each case the maximum output of the sun is 1,366.42 ± 0.009 watts/m2 -
there is no increasing solar irradiance over the past 30 years. The difference
between solar maxima and minima over these 11 year cycles is 0.905 w/m2 (0.07%
of solar output) - there is no significant fluctuation of the solar minima
either. So it seems highly unlikely that changes in solar activity can account
for rising global temperature in the last 30 years. The 4th assessment report
of the IPCC specifically addresses this issue as well. It states:
“Changes in solar irradiance since 1750 are estimated to cause a radiative
forcing of +0.12 [range:+0.06 to +0.30] W/m2, which is less than half the
estimate given in the TAR.”.(TAR = Third Assessment Report) The net radiative
forcing from all contributors, says the IPCC, is 1.6 [range +0.6 to +2.4]
watts/m2, so that changes in solar irradiance accounts for lass that 10% [the
very maximum it could contribute if the IPCC numbers are right is 50% and the
least it could contribute is 2.5%] of the climate forcing being measured.
It seems that we should not put too much credence in the documentary’s
assertions that solar variance is responsible for our changing climate.

Conclusion
Although initially convincing to an educated lay viewer - especially a viewer
that is eager to hear that we do not have to make any changes in our Western
lifestyles - more careful analysis and attention to the scientific literature
makes it difficult to avoid labeling this effort as a politically driven
screed. Certainly the malicious castigation of the integrity of the mainstream
scientific community contained in the commentary does not lend strength to
their argument; instead it does just the opposite. An honest accounting of ones
position based on the best science available should not necessitate impugning
your opponent’s intentions nor should it require a distortion of the
scientific record. This documentary appears to do both.

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 11:40:47 2007