France: Third Rock From the Sun

In January, Jean-Louis Dufresne, a member of the French Natl. Research Inst., came to Total’s headquarters to present a lecture on how human activities are affecting the Earth’s climate. Fifty people attended, both young professionals and more-experienced workers, to hear this French specialist who has studied the subject for 15 years.

The Earth’s climate is warming because of the greenhouse effect, he said. This physical phenomenon has been known since the 19th century, when scientists discovered infrared rays. At that time, Arrhenius predicted that a change in the CO2 concentration in the atmosphere would change the Earth’s surface temperature.

The main greenhouse gases are water vapor and CO2. The greenhouse effect is caused when those gases are transparent to solar rays but impenetrable to infrared rays (that are emitted by the Earth). Dufresne said that climate change because of human activity has been confirmed recently. Historical observations from ice cores show that the CO2 concentration in the atmosphere has oscillated between 180 and 290 ppm for 650,000 years. But since the beginning of the industrial development in the middle of the 19th century, that concentration has risen to 370 ppm today.

During that same period, the average surface temperature of the Earth rose about 1°C in 150 years, he said, compared to a stabilized temperature in the previous 1,000 years. Representing the Earth’s climate with numerical modeling started in the 1970s and has become increasingly accurate, he said. Today, most models cannot reproduce the last century's temperature increase without considering recent human development and its impact on the carbon cycle (the change in the composition of the atmosphere and land-surface modifications).

Those models, once matched with the historical data between 1800 and 2000, are simulating different development scenarios for the coming century, Dufresne said. All predict a temperature increase of 1.5 to 3°C in a low-emission scenario and 3 to 5.5°C in a “business as usual” scenario for the year 2100.

The consequences of that climate change are not predictable, he said. What we know is that a decrease of the average surface temperature of 5°C from today is an “ice age,” Dufresne said. He concluded by saying that we are now entering a climate era that has not been observed in 650,000 years. It seems clearer every day that our economic development is introducing greenhouse gases into the atmosphere and that this is not sustainable and will lead to major environmental and eventually human disaster, Dufresne contended.

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