• Issue 2

 Temperatures in the last 400,000 years have fluctuated dramatically, by more than 10 degrees (see graph). That is not due to greenhouse anomalies, but to the fact that the Earth is like a spinning top , which oscillates and changes its inclination towards the Sun while orbiting.

This phenomenon was clearly described by Copernicus and firstly understood, like many other things, by Isaac Newton (1687).

There are three different oscillations in temperature. The biggest oscillation, with a period of 100,000 years, causes variations of up to 10 degrees. In addition to that, there are two more periodical variations, one of 41,000 years, the other of 23,000 years. Click on the graph to see more.

These big fluctuations in temperature have always influenced life on Earth. At its coldest, the ice age appeared, and the rain decreased. In the last ice age, 18,000 years ago, archaeological studies show that the Nile and lake Victoria in Africa disappeared.

As more water was trapped in the ice, which covered a good part of the planet, Europe included. In addition, there was less vapour in the sky, therefore less rain and less greenhouse gas effect, and the situation got worse.

In the last 18,000 years the temperatures on Earth have increased, and so have the number of human beings - they had just collapsed during the last ice age. The picture shows that we could "geologically soon" (2-3,000 thousand years) enter a cooling period. And in the history of humanity, cold periods have always been bad, as many archaeological studies have shown.

Temperature and CO2

In the last 400,000 years, temperature and CO2 concentration have gone up and down, like an old couple. They are intricately linked, as Al Gore says in his documentary An Inconvenient Truth. But in a different way to what Gore thinks. Indeed, some scientists think that when temperatures increase, CO2 goes the same way, with a time delay of about 600 years.

Hubertus Fischer, Martin Wahlen, Jesse Smith, Derek Mastroianni and Bruce Deck, in their article Ice Core Records of Atmospheric CO2 around the Last Three Glacial Terminations, for the Science magazine, write that "high-resolution records from Antarctic ice cores show that carbon dioxide concentrations increased by 80 to 100 parts per million by volume 600 ± 400 years after the warming of the last three deglaciations."

Some others, think that the huge movements in temperature are known to be caused by anastronomical effect. That means that the 100,000, 41,000 and 23,000 periods in the Earth's temperature oscillations do not originate from greenhouse gases.


There are, then, some points that are hardly mentioned in the news. The environment in the past has been more human-friendly during warm periods than during cold periods. Carbon dioxide may amplify the effect, but warming in the past has originated by other causes than CO2 increase. In addition to that, the molecule of water is a much more powerful greenhouse gas (see the previous article).

Should we then burn as much petrol as we like? Not at all. Why? This should be the issue of the next article.

[1] H. Fisher et al., Ice Core Records of Atmospheric CO2 around the Last Three Glacial Terminations, Science, 12 March 1999.

Graph: scientists took a long sample of ice in some thousands of years old glaciers, and measured the quantity of CO2 dissolved in it. Measuring the different types -isotopes- of Hydrogen they could also guess the temperature. Source: United Nations Environment Programme/GRID-Arenda. Picture published according to the licence.