WHILE IT’S HOT!

Will our regions see a new ice age?
On the influence of carbonic acid on atmospheric temperature

Is it nice to talk about the cold during the heatwave? Is the memory of what you miss consoling? Dante once argued about this with Musset, Dante replied in the negative; Musset, on the contrary, affirmatively. In this controversy between poets, Musset had the last word. This was for chronological reasons. Yet it seems to me that he was right. The memory of the past charms us because, reflected in the mirror of time, it reflects hope and we always expect to find what we have lost. I therefore believe the time has come to mention here these glacial periods which once raged in our regions and which could well be resurrected soon, as we will see.
The current era of the Earth, the Quaternary period, saw the appearance of man, a mediocre sidekick in the geological drama, and above all the succession of glacial periods and warm periods which have alternated several times here on earth. This is clearly proven by the examination of moraines and erratic blocks, of those rocks transported by the front and flanks of glaciers, and which are found in various terrains.
It follows with certainty that there were at least two very cold glacial epochs in the past, separated by a warm interglacial epoch. During these, the glaciers extended to the center of France. The Vosges and Auvergne were covered with them. In the Alps themselves, they occupied 150,000 square kilometers, instead of 4,000 today. Then the mammoth and other species with thick hair reigned among us, and whose fossils also attest to the cold which reigned then. The end of the last ice age appears to date back ten thousand years at most. Are we not now in a new temporary interglacial period and can we not expect to soon see a cooling of our climates again? This is very probable, if we are to believe the ideas which have recently been developed in this regard by the Swede Arrhenius.
Curiously enough, the cause of these variations appears to be the carbonic acid existing in our atmosphere and which nevertheless only occupies barely three thousandths of its volume. This gas has the property of acting like the glass of a greenhouse and that, allowing the warm light of the sun to reach the ground, it on the contrary stops the dark heat rays that the ground emits towards space when it cools down.
The consequence is that if the current carbonic acid in our atmosphere completely disappeared, the temperature near the ground would decrease – the calculation shows – by 21 degrees on average. If only half of this carbonic acid disappeared, the average temperature would decrease by 4 degrees. If, on the contrary, the level of this gas doubled, it would increase by 4 degrees. However, the quantity of carbonic acid contained in the air depends, on the one hand, on the plants which absorb it for nourishment, and also on certain minerals such as lime which combine with it. On the other hand, and on the contrary, these plants, when they decompose or burn, release part of this carbonic acid into the air; volcanoes also release it, and also all industries that consume coal. These quantities are not negligible and we can calculate that the 1,200 million tonnes of coal consumed annually by humanity release one five hundredth of its carbonic acid content into the atmosphere. But, on the other hand, plants absorb ten times more, returning part of it, but burying the rest in the soil.
The question is therefore to know whether the emission of this gas by Volcanoes, by human industry, by all combustion and by the respiration of all living beings exceeds its absorption and burial by plants, or, on the contrary , is inferior to them. In the first case, our climate is warming up, in the second, on the contrary, it is cooling, and in a few thousand, in a few hundred years perhaps, France will again be covered with ice cream, which will eliminate in July, some of the sweaty complaints that we are hearing about at the moment.
In any case, it is very curious, this property of a gas, relatively rare in the atmosphere and whose proportions can be sufficient to modify the climate. Through it, everything that increases vegetation tends to cool the air, in the short term, everything that increases industrial and animal combustion tends to heat it. So when you light your stove in winter, don't forget that to a certain extent you are contributing to raising the temperature it will be the following summer. And when you plant rose bushes, remember that they will make the air a game colder next winter.

Charles Nordmann