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A theoretical model demonstrates that the quantity of energy received by an object in the solar system diminishes in proportion to its distance from the Sun, what is called the solar constant. The further an object is from the Sun, the smaller is the quantity of energy that it receives. If this model is followed, the mean temperature on the surface of the Earth should be -18 °C. In fact, the mean temperature is 15 °C, which is compatible with the existence of water in its three physical states. (see picture 1)
What, then, is the reason for this clement temperature , favourable to life on Earth ? The mathematician Joseph Fourier (1768-1830) (see picture 2) was one of the first scientists to attribute a role to the atmospheric gases in the determination of temperature levels ruling on the Earth’s surface.
In 1804, he sketched out a definition of the greenhouse effect whilst studying energy balances as part of his work on heat. The planets receive energy in the form of solar radiation and lose it in the form of infrared radiation.
It was John Tyndall (1820-1893) (see picture 3), an Irish physicist, who highlighted the role of water vapour in the existence of a greenhouse effect. He worked out the «climatic theory of carbon dioxide » and predicted that a variation in atmospheric composition, in terms of water vapour (H2O) and carbon dioxide (CO2), would give rise to a change in climate. |