Changes in climate can be caused by changes in Earth’s atmosphere, as well as changes happening in other Earth’s systems. Oceans and glaciers are examples of such systems. Nowadays, human activity also has considerable effects on the climate change. These causes originate within the Earth itself and are, therefore, known as internal causes. Among external causes of the climate change are changes of solar radiation or changes of Earth’s rotational orbit.
The most common causes of the climate change (both external and internal) are:
- Changes of the sizes, landscapes and relative positions of oceans and continents;
- Changes in Solar luminosity;
- Changes of the orbit and the axis of Earth’s rotation;
- Changes of the constitution and the transparency of the atmosphere. This includes changes in the greenhouse gas concentrations (like CO2 and CH4);
- Changes in the albedo – the reflection of the solar radiation by Earth’s surface and atmosphere;
- Changes in the amount of heat stored in the world ocean.
Non-anthropogenic factors
Plate tectonics
The movements of the tectonic plates change the surface of our planet. These movements are very slow, however, the changes caused by them are dramatic. The Earth’s crust is divided onto 12 major tectonic plates. Their movements result in changing positions of the continents, formation of the oceans; they can also create and destroy mountain chains. All in all – the tectonic plates create the surface on top of which the climate forms.
Recent investigations have even demonstrated that tectonic plates movement has enhanced the consequences of the last ice age. About 3 million years ago a collision of 2 tectonic plates – the North-American plate and the South-American plate – caused the creation of the Isthmus of Panama. This has consequently prevented the direct mixing of the waters of the Atlantic and the Pacific oceans, which, in turns, had dramatic influence on the climate of the Earth.
Solar cycle
The Sun is the main source of heat in the climate systems of the Earth. Moreover, if we consider very long periods of time, the intensity of the solar radiation is slowly increasing. This happens due to the fact that the Sun is developing according to the laws of the main sequence stars.
Milankovitch cycles
The eccentricity of the Earth orbit, as well as the direction and the angle of its axis, are regularly changing. These changes lead to the redistribution of solar energy on Earth’s surface. They are usually referred to as “Milankovitch cycles” and can be accurately predicted. There are 4 Milankovitch cycles:
- Axial tilt (obliquity) is the angle between the equatorial plane of a planet and its orbital plane. The period of this cycle is approximately 41000 years;
- Axial precession is the change in the direction of the Earth’s axis caused by the Moon and the Sun. This cycle has a period of 25771.5 years;
- Apsidal Precession
- Orbital Inclination
Volcanic eruptions
A strong volcanic eruption can cause noticeable climate change, generally lasting for several years. Generally, volcanic eruptions lead to the cooling down of the surface of the Earth. Very rarely – several times per hundred million years – gigantic volcanic eruptions take place. They can cause significant temperature drops lasting for millions of years. Moreover, such volcanic eruptions result in the extinction of species of plants and animals.
Check the following website for more information about external factors of climate change.