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Climate Modeling Must Consider All "Greenhouse" Gases

Jan Veizer knows it is not politically correct to suggest that carbon dioxide is not the primary culprit in global warming. But he does argue that it is scientifically correct to say so, and he has 20 years' worth of acclaimed research to support that opinion.
Ottawa - Dec. 6, 2000
Global warming is a lot more complicated than is generally assumed, and we may have to rethink how we deal with the issue says University of Ottawa and Ruhr University (Germany) geologist Jan Veizer and his colleagues from Belgium who have assembled a very different picture of the physical and chemical conditions that have contributed to the past warming or cooling of our planet.

An increase in the atmospheric volume of "greenhouse" gases such as carbon dioxide -- which has been blamed as the primary cause of recent increases in the world's average annual temperature -- is just part of the story.

In an article being published this week in the definitive scientific journal Nature, Veizer and colleagues conclude that past climates and estimates of carbon dioxide concentrations disagree. An increase in the level of greenhouse gases may be a natural side effect of climate change.

Our own industrial contribution may enhance a given natural trend but not reverse it. The release and consumption of carbon dioxide goes hand in hand with other greenhouse gases.

In order to mitigate our impact on this balance, we should take into account the cumulative role of all greenhouse gases, particularly of water vapour as the leading agent that modulates our climate.

Jan Veizer knows it is not politically correct to suggest that carbon dioxide is not the primary culprit in global warming. But he does argue that it is scientifically correct to say so, and he has 20 years' worth of acclaimed research to support that opinion.

"It needs a bit of perspective, that's all," he says.

His perspective covers the last 550 million years of the earth's history. That's how far back he and his colleagues have been able to measure the amounts of chemicals found in marine shells from around the world.

These reveal major changes that took place in the amount of oxygen isotopes in seawater, a key indication of changes in temperature associated with major climatic events such as ice ages.

It was thought that those events were restricted to certain parts of the globe, but the work of Veizer and his colleagues has revealed that tropical areas cooled down at the same time.

Since warming and cooling trends have usually been credited to changes in the levels of the notorious "greenhouse" gas, carbon dioxide, and the results disagreed, the observations challenged the existing model. In particular, Veizer wondered where the atmosphere's excess CO2 went so that the world could cool down.

Trees and soils are often seen as the most important "sinks", where CO2 and water are absorbed from the air and soil. That is why much of the environmental debate that took place in The Hague last month focused on the world's forests.

If we are responsible for warming up the planet by pumping more carbon into the air by burning fossil fuels in our automobiles and elsewhere, then a sufficient amount of forest cover should be able to remove this carbon from the atmosphere.

Yet Veizer suggests that the situation is much more complex. Based on work with his former student K. Telmer, presently at the University of Victoria, he argues that there is a crucial link between the way carbon and water each cycle through plants, the atmosphere and the ground.

In order to fix one molecule of carbon, a plant has to transpire almost one thousand molecules of water.

Yet, the air and soils contain less than one hundred molecules of water to each molecule of carbon dioxide. The system is therefore water, not CO2, limited. With warmer climate, and greater humidity, forests may play an enhanced role in the CO2 budget of the atmosphere.

That may be cold comfort to our environmental agenda, which should be more inclusive and consider all greenhouse gases, not just CO2. In particular, it should take into account the modulating role of the most important greenhouse gas, water vapour.

Veizer is sympathetic to arguments that we should reduce pollution. He simply does not want those arguments to be premised on incomplete science. And on that basis he suggests that we should in fact continue with plans to lower CO2 emissions, even if it is for entirely different reasons.

"In the end, I am all for it, because it is in fact pollution and we only have one planet to live on," he says.

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Polar Bears May Have To Move North
Churchill - Dec. 9, 2000
Images of our north as a vast expanse of snow, cold and ice have been part of the Canadian identity for generations. This excerpt from a poem written by Professor William Gough of the environmental science department at Scarborough both affirms this image -- and mourns its passing.



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