Sun and climate

If the Earth rotated around the sun in a perfectly vertical way like a spinning top, the weather wouldn’t vary during the year, in other words there wouldn’t be any seasons, because the amount of solar radiation reaching the planet’ surface would always be the same. If the earth’s axis wasn’t at an angle with respect to the orbital plane, not only would there be no seasons, but neither could there be any differences between one hemisphere and the other and obviously the tropics would not exist. Instead, fortunately for us, during the year the inclination of earth’s axis with respect to the solar rays changes thus varying the angle at which they reach the planet. Therefore on the 21st of June, summer solstice, the solar rays are perpendicular to the imaginary line called Tropic of Cancer in our hemisphere; while the 22nd of December, which is winter solstice in our hemisphere whereas it is summer in the Austral one, solar rays are perpendicular with respect to the imaginary line called Tropic of Capricorn which is in the southern hemisphere. During each equinox, instead, solar rays are perpendicular to the Equator. Rays that reach the ground perpendicularly have the maximum atmosphere penetration power and the maximum thermal effect at both tropics, which is why the tropical belt is the area with the hottest and most constant climate all year round. Climate variation increases as one goes north towards the boreal hemisphere and south towards the Austral one. The temperature difference among the various latitudes trigger the complex climatic thermodynamics which actually are influenced by many other factors: local geology, the presence of large water masses or high altitudes and atmospheric conditions. A clear example of how the local geography influences climate is the Assuan dam that created the Nasser Lake, PIC21 a huge artificial basin that had deep implications not only on the region’s weather, but also on the southern Mediterranean area. Before it was built it was impossible to imagine that it would affect the weather so heavily and from that we have learned that weather dynamics are really complex phenomena to foresee with mathematical precision.

Special reports

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    Save the air

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  • air

    The greenhouse effect

    Look

    ecosystems

    Deforestation

    Look
  • air

    Albedo

    Look

    air

    Future scenarios of an increase in the temperature

    Look
  • air

    Icebergs, ice packs and glaciers

    Look

    air

    Mean sea level rise foreseen by IPCC

    Look

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