Posts Tagged ‘long term’

Climate machine: the moving Earth

Sunday, January 17th, 2010

The climate of the Earth changes due to the way it moves – we are talking about seasonal changes in tens of thousand years.

The Earth wavers slightly in it’s elliptical rotation around the Sun. This is caused by the forces of attraction between the planets. The wavering is periodical and can cause climate change both locally and globally as the incidence of solar rays falling on the Earth changes with the relative position of the Earth. There is research going on to quantify these changes. The Jugoslav Milutin ┬áMilankovic in 1941 was the first to describe these changes.

The are three types of wavering or movement:

1. The elongation of the Earth’s elliptical path changes over about 100.000 years. The energy the Earth receives varies with about 30% due to this effect, and with maximum elongation of the ellipse the solar incidence over the year will vary most giving extreme weather.

2. The angle of the Earth’s axis changes between 21.8 and 24.4 degrees (axial ties). A low value of angle means there is less difference between the seasons and less violent weather, whereas a high value gives more extreme weather. A fuul change of angle takes about 41.000 years.

3. When the The Earth rotates around its own axis the axis describes a circle taking about 22.000 years to complete (axial precession). This make the seasons move relatively to a fixed calender.

Other changes that matters are changes in the Earth’s surface that will lead to changes in the ocean currents and the flow of air. This takes millions of years. Earthquakes and volcanoes can have big influence on climate for a long time. Man-made changes also matters: deforestation, big rivers being led in new directions, lakes drying up.