Explain the natural causes of climate change (10 marks)

Taking temperature as an indicator of climate, there have been huge changes over Earth’s history. Temperatures have been much higher at some points in the past than they are today. We can look at the geological past and see natural causes behind many of these variations.

There are three types of reasons why the earths climate will variate. The first is due to the activity of the sun. In a cycle lasting around 10 years, sunspots will appear of the surface of the sun. The more dark spots appear, the more solar radiation is emitted, and therefore the earth receives more heat from the sun. This can cause a period of increased heating. If the sunspots are less numerous, the earth’s climate may decrease.

Another cause is due to earth tectonic activity and volcanoes. When a particularly explosive volcano erupts, it often ejects large quantities of ash and tephra into the atmosphere. This prevents the incoming solar radiation from entering the atmosphere, therefore causing the climate to experience a cooling. An example of this is Mount Pinatubo in 1991, in which the earth’s temperature fell almost by 0.5C

Lastly, the climate may change due to changes in the earths rotational cycle, called the Milankovitch cycle. This is when the earth’s orbital shape around the sun changes from elliptical, to circular every 100,000 years, therefore changing the amount of solar radiation that the earth may receive, meaning that it may get warmer or colder. Another change is in the earth’s tilt, which may change degrees, allowing different areas to be exposed to more solar radiation. In an even more complex turn, the earth may “wobble” on its axis, which may cause further variation in climate.