The climate of the Earth varies because of a number of
factors. Key to this variability is the relationship between the
Earth and the Sun. Temperatures on Earth depend on energy from
the Sun. This energy is not distributed evenly across the Earth’s
surface and varies with latitude. Away from the equator, the Earth’s
curved surface means that each ‘beam’ of sunlight is spread over
a greater area and must pass through a greater thickness of atmosphere.
So the solar heat energy reaching the Earth is more intense at
the equator than it is at the poles. Rays of sunlight sometimes
emerge from breaks in cloud like searchlight beams. The rays become
visible when sunlight is scattered by dust or fine raindrops.
The rays are in fact parallel and the apparent spreading is a
trick of perspective.
The energy of sunlight is lost as it passes through the
atmosphere by absorption and scattering. The scattering
of light by gas molecules and dust particles makes the sky look
blue. The sky is lightest blue where there is the most gas and dust
near the surface of the Earth, but this turns to black as you head
up towards space. In addition, there are many different types of surface on Earth and these have different abilities to absorb or
reflect the heat from the Sun. We call the amount of reflectivity
a surface has its ‘albedo’.
