Veizer sheds light
on the controversy
about global climate
by: Colin Rowe
by Tim Lougheed
Professor Jan Veizer has waded into the ongoing debate over the
mechanics and dynamics of global warming. In an article published
in Nature on December 7, 2000, he added a detailed geological
perspective on how the worlds climate has changed in the past,
and how it could be changing today.
The most widely publicized views on the
matter surround the key role of carbon dioxide (CO2),
which has been hailed as the primary greenhouse gas.
Its rising concentration in the earths atmosphere is often
credited with trapping heat and raising the planets average
temperature. International agreements, such as the one struck in
Kyoto, Japan in 1997, have suggested that this change has been caused
by industrial pollution, which should be reduced to minimize the
environmental impact of the warming trend.
Veizers paper, Evidence for decoupling
of atmospheric CO2 and global climate during the Phanerozoic
eon, adds a different perspective on the matter. Co-authored
with Yves Godderis and Louis M. François, of the Laboratoire
de Physique Atmosphérique et Planétaire at the University
of Liège in Belgium, the paper points to the unclear causes
for the ice ages and warm periods that have punctuated the earths
climate throughout the last 600 million years. Using marine fossils
found in sedimentary layers from different eras, they were able
to establish past ocean temperatures that agreed with semiquantitative
climate reconstructions based on distribution of climate sensitive
rock types. Using past CO2 estimates from others and
applying the current climate models, they then calculated temperatures
for the same time intervals. The results were disappointing, with
very high CO2 levels and temperatures in the midst of
The climate pattern mandated by these
observations may require reconsideration of the role of CO2
as the principal driving force of climate changes on geological
time scales, they concluded.
Since the publication in Nature,
some media reports, depending on their political bent, have approvingly
claimed that Veizer has deflated the greenhouse theory,
while others have taken him to task for implying that CO2
is not a greenhouse gas. Critics have either claimed that the publication
is of no relevance to the understanding of the present greenhouse
or have charged him with giving industry a scientific justification
to go on polluting, suggesting that our civilizations contribution
of CO2 in the atmosphere will make little or no difference
to the earths climate.
Veizers own paper makes no such claim,
but an accompanying commentary in the same issue of Nature, What
drives climate?, came much closer to doing so.
Such a conclusion deserves close scrutiny,
because the policy implications are huge, wrote Pennsylvania
State University geoscientist Lee Kump. If large changes in
atmospheric CO2 in the past have not produced the climate
response we thought they had, that undermines the case for reducing
Veizer did not know that Kumps comments
would be published alongside of his own work. Nevertheless, he has
had to respond to queries and criticism as though he had been the
author of these comments.
I never said CO2 was not
a greenhouse gas, he says. But there is this one political
dogma: CO2 equals global warming, equals climate change,
equals disaster. Now, the further you go along this equation, the
iffier it is scientifically. But the moment you step away from this
dogma you are excommunicated. You are undermining the environmental
agenda. He adds that he never intended to attack anyone who
wants to preserve the physical integrity of our planet. But he does
worry that if such efforts depend on incomplete or flawed science,
the predictions could well prove to be inaccurate and the entire
environmental agenda could be discredited.
Veizers work has attempted to clarify
existing models of climate change by enhancing their accuracy. He
and his colleagues have been working with new databases for isotopes
of strontium, oxygen and carbon. Their findings have offered the
first quantitative estimates of seawater temperatures at different
points in the earths history over the last 550 million years.
Combining this information with records of the major shifts in climate,
he notes that CO2 is not a driver of such changes, but
simply amplifies an effect that has already been started in some
In fact, he points to other research revealing
that the amount of water vapour in the earths atmosphere is
a far more influential factor in modulating major shifts in global
temperatures. And while water vapour is far from alone in its impact,
its importance demonstrates that the climatic system is much more
complex than would be allowed by any model suggesting that CO2
is the only reason the earth is warming today. Water must
play an important role also in the proposed half a degree Celsius
warming over the past century, says Veizer. It is the
relative importance of CO2 and the degree of warming
that is a matter of debate, not the greenhouse itself.
He adds that he is well aware that this
idea is not politically welcome. But he concludes that it is scientifically
correct to say so, and he has 30 years worth of acclaimed
research to support that opinion.
It needs a bit of perspective, thats
all, he says.