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Keith Dancey · December 21st 04, 03:54 PM posted to uk.sci.weather

In article , "Gavin Staples" writes:

"Jim Webster" wrote in message
...

Whilst there probably are people in global warming denial, there are others
who are perfectly willing to accept that global warming is happening, but
doubt just how much impact humanity is having on the process.

I go along with the idea that warming is taking place but I am sceptical
with regard to the assertions that humans are entirely responsible.

Apologies for being late on this one (chemotherapy), and to answer Jim
and Gavin's sceptism, the evidence for the anthropomorphic contribution
to global warming lies in the increase in atmospheric CO2.

That atmospheric CO2 has increased is undeniable: it is long-lived, well
mixed and subject to direct and indirect measurement. The increase is
more than 30% over the last 100 years.

That CO2 is a greenhouse gas is also undeniable: it is easily shown in a
laboratory and an increase in partial pressure of the magnitude we have
experienced is highly significant.

That the increase is due to human economic activity is demonstrated by the
ratio of carbon isotopes in atmospheric CO2. The proportion of Carbon-12
to the other stable isotope of carbon, in the atmosphere, has been measured
and found to be increasing. The only source of such an isotope is carbon
released from burning fossil fuel (and not wood, for instance).

This change in carbon ratios in atmospheric CO2 ties in with the recent
increase in CO2.

Cheers,

keith

---
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