PLEASE NOTE:
*
Date sent: Mon, 13 Oct
1997 09:49:52 -0400 (EDT)
From:
Benny J Peiser <B.J.PEISER@livjm.ac.uk
Subject: IS
THE EARTH REALLY GETTING HOTTER?
To:
cambridge-conference@livjm.ac.uk
Priority: NORMAL
BAD NEWS FOR PESSIMISTS, DOOMSDAY PROPHETS & ECO WARRIORS:
SATELLITE DATA FAIL TO DETECT GLOBAL WARMING
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from: THE TIMES, 13 October 1997, p. 15
IS THE EARTH REALLY GETTING HOTTER?
By Nigel Hawkes, Science Editor
Man-made global warming is increasingly accepted as a fact.
The most
recent expert to give it his imprimatur is the [UK] Government's
Chief
Scientist, Sir Robert May. Pretty soon, it seems safe to say,
politicians
will be justifying higher taxes on fuel on the ground that the
future of the
world depends on cutting the output of carbon dioxide. Yet there
are still a
few awkward problems with the theory that refuse to go away.
The most striking remains the actual temperature measurements
over the past
century. At ground level, they have risen by between 0.3 and
0.6C,
significantly less than computer models of the atmosphere would
have
predicted. But even this relatively small increase is thrown into
doubt by
measurements of the temperature of the lower atmosphere taken by
satellites
looking down from space, which show no increase at all over the
past 20
years, or even a slight decline.
Naturally, the satellite measurements have been subjected to
some tough
critical analysis. Errors are alleged to have arisen because the
temperatures have been measured not by a single satellite but by
a series,
whose instruments were imperfectly calibrated. When one took over
from
another errors arose, and actual increases in temperature went
undetected.
In other words, the satellite data are wrong and can be
discarded.
Not so, say the satellite's champions, Dr John Christy, of the
University of Alabama, and Dr Roy Spencer of the American space
agency
NASA's Marshall Space Flight Centre in Alabama. In a recent issue
of NATURE,
they rebut the criticisms by pointing out that not only have
careful
calibrations between the satellites proved that they are
measuring the same
thing, but that the satellite temperatures have been confirmed by
balloon-borne observations of exactly the same part of the
atmosphere. The
results, they say, show that the satellite temperatures are
accurate to
three one hundreths of a degree (0.03C).
So what is going on? Christy and Spencer do not deny that
increases in
carbon dioxide should have some effect on the Earth's
temperature, but they
believe that the effect is tiny compared with other processes.
Among these
is the presence in the atmosphere of water vapour, a far more
powerful
greenhouse gas than carbon dioxide, and extremely variable both
in space and
time. They suggest that the temperature of the lower atmosphere
is not
determined by the balance between incoming solar radiation and
outgoing
infra-red radiation, as the models require, but by processes of
evaporation
and convection which transfer heat to the upper troposphere. Once
there, it
is above the heat-trapping water vapour.
Despite the satellite's inability to detect evidence of global
warming, it
does show up the fluctuations in temperature caused by volcanic
eruptions
and the El Nino effect. Infra-red images from satellites also
show extremely
dry areas of the atmosphere over the Tropics which, the
scientists
speculate, may be "chimneys" that allow heat to radiate
freely into space.
The effects of these areas of dry troposphere are not well
understood, nor
are they effectively incorporated into the computer models of
global
warming.
In an ideal world, the clash of evidence would be sorted out
before we
embrace carbon taxes with all the implications they have for
future
prosperity. But most experts seem prepared to disregard the
satellite data.