GCSE Geography | Natural Causes of Climate Change (Climate Change 3)

There are several natural causes of climate change.

Orbital changes

Serbian geophysicist Milankovitch studied the earth’s orbit and spotted 3 different cycles that he claimed to affect global climate – these are called Milankovitch cycles – and they affect the timings and seasons of earth’s climate.

• Eccentricity - this describes the orbital path, which changes from being almost circular to slightly elliptical – a complete cycle of this takes roughly 100,000 years – which coincides with alternating glacial and interglacial periods.
• Axial tilt - we know that the earth spins on an axis and this axis is tilted – at 23.5 degrees. But over 41,000 years it will move back and forth between 21.5 and 24.5 degrees.
• Precession - which is a natural wobble which is why some places around the world have very long days or very long nights at certain times of the year – a wobble cycle takes 26,000 years.

Solar output

The presence of sunspots on the sun’s surface can affect global temperatures. Sunspots are dark patches that appear from time to time – increasing from a minimum to a maximum over a period of 11 years, which is called a sunspot cycle. When sunspot output is at a maximum the sun will give off more heat, which can make large explosions occur on the surface and can result in solar flares. When it is at a minimum this reduces solar output, which could lead to lower temperatures on earth. Long periods with very few sunspots are sometimes referred to as little ice ages where the climate will be much colder with severe winters.

Volcanic activity

When volcanoes erupt in an explosive fashion they send huge amounts of lava, ash, gases and rocks into the atmosphere. This affects the temperature in two ways.

Firstly, volcanic ash can block out the sun – this is a short term impact but it can reduce the earth’s temperature temporarily.

Secondly, the sulphur dioxide that is given off is converted into sulphuric acid, forming fine droplets – which then reflect the sun’s radiation leading to a drop in temperatures which can last for many years. The 1815 eruption of Tambora in Indonesia is a good example of this – the ash and sulphuric acid caused average global temperatures to drop by between 0.4 and 0.7 degrees – and 1816 was called the year without summer – it also led to harvests failing right across the globe – causing 200,000 deaths from famine in Europe alone.