Climate Change: A Longer View

By Prof. Bob Carter (Published  05/03/2004)

Over the last two years, the scientific framework within which an 
assessment of climate change is made has undergone dramatic revision.
Not all at once, but inch by inch, in increments of understanding.

First has come the rigorous external review of some of the key
findings and recommendations of the Intergovernmental Panel on Climate Change
(IPCC), as contained in its last "advice to governments" report in
2001.  Review of the IPCC report has been accomplished mainly by freethinking persons
who are often referred to in derogatory terms as "climate
skeptics" or "contrarians".  In fact, those who have criticized the IPCC
findings include many outstanding professional persons in their own right,
nearly all of whom see themselves as climate "agnostics" rather
than "skeptics".  That is to say, they have no preconceived
beliefs about the current pattern of climate change, nor any particular expectation for 
change to occur one way or the other.  They are, however, united in
their wish for the public to be informed of the main facts and conclusions
about climate change -- free of any political agenda or IPCC intrigue.

Sadly, a foremost Australian member of this group died recently. 
John Daly, a retired Tasmanian engineer, maintained an eponymous web site 
devoted to critical analysis of climate change science.  Together
with another similar site maintained by Sherwood Idso, a senior scientist
from Arizona, Daly's web site provided critical and dispassionate
discussion of the torrent of Frisbee-science which today masquerades as discussion
of climate change in the daily media.  These web sites, and other 
publications, have drawn attention to the increasing shakiness of the
three main arguments that comprise the IPCC case for a human influence on
climate change.

Three Arguments

Argument one asserts that ground-based temperature measurements have
been corrected adequately for environmental effects, including especially
the urban "heat island" effect, and that the pattern of global
change in temperature which results -- about a 0.60 C increase over the last
100 years -- is likely to have a human cause.  In actuality, that part of
the claimed increase in temperature which occurred over the last 25 years
is contradicted by two alternative measurements of atmospheric
temperature made from weather balloons and satellites, the patterns of which
agree with each other and show little or no long-term trend of temperature
change.  At the very least, this discrepancy casts doubt on the adequacy of the 
heat-island correction that has been made to the surface records.

Argument two, after papers by statistician Michael Mann and
co-authors, asserts that both the peak magnitude and the rate of temperature
increase over the last 100 years are exceptional by comparison with the
preceding 900 years.  But recent published papers by other scientists have
demolished this argument and shown that Mann's work is statistically unsound. 
Both its historical analysis and its projected peak of warming at the
recent turn of the century are now known to be flawed.  And anyway,
irrespective of recondite statistical arguments, many earlier published geological 
studies show that the rate and magnitude of climate change over historic times lies within the envelope of natural variation.

The third IPCC argument rests upon complex computer models, which
attempt to predict the rate of warming for the increasing rate of carbon
dioxide in the atmosphere through to the year 2100.  However, these models are
unable to simulate 20th century climatic history accurately, and also fail
when tested against the last 25 years of accurate data from satellites and 
weather balloons.  A primary reason for the mismatches is probably
that the computer models assume an unrealistically high temperature
sensitivity for atmospheric greenhouse gas accumulation.

The flaws in these three IPCC arguments are cumulatively fatal.  But,
in addition, it has become increasingly apparent lately that the
1,000-year interval, which is the context for most IPCC advice and analysis, is
a completely inadequate period over which to assess global climate 
change.  The focus of discussion, therefore, is shifting away from
the short-term mechanisms studied by meteorologists and climatologists,
to the knowledge base for climate change that exists in the geological
record over tens and hundreds of thousands of years.

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Professor R.M. (Bob) Carter (Hon FRSNZ) is a geologist at the
Marine Geophysical Laboratory of James Cook University in Townsville,
Queensland, AUSTRALIA
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