Archivo para febrero 21st, 2020



















The relative stability of Earth’s temperature suggests a near balance between planetary input and output of energy. The input is almost entirely solar radiation, which amounts to 173,000 TW (173,000 × 1012 W). Besides solar energy, there is a contribution from tides (3 TW) and from heat sources inside the planet, mostly radioactivity (32 TW). Some 52,000 TW (30% of the incoming radiation) is reflected back
to the interplanetary space: it is the albedo of Earth. All the remaining energy is degraded to heat and reemitted as long-wave infrared radiation. Figure shows the different processes that take place in the planetary energy balance mechanism. The recurrence of ice ages shows that the equilibrium between incoming and outgoing energy is oscillatory. It is feared that the observed secular increase in atmospheric CO2 might lead to a general heating of the planet, resulting in a partial melting of the Antarctic glaciers and consequent flooding of sea-level cities. The growth in CO2 concentration is the result of the combustion of vast amounts of fossil fuels and the destruction of forests in which carbon had been locked.