Skip to content. | Skip to navigation

What is climate change?

What is climate change?The Earth is warming up - but why is it happening and is it really our fault?

The Earth’s climate does not stay the same, it has changed a lot over time, including going through four major ice ages. The accumulation of snow and ice during a glacial period means more of the sun’s energy is reflected into space which gives the Earth a lower atmospheric temperature. Ice Ages end when changes in the Earth's orbit, changes in the solar output, or volcanism bring about a rise in the temperature.

What are ‘greenhouse gases’?

The Earth is surrounded by a layer of gases which act like the glass walls of a greenhouse: they let the sun’s rays enter, but stop much of the heat from leaving. This is a natural process, and it is this layer of ‘greenhouse gases’ (mainly carbon dioxide and water vapour) that keeps the planet warm enough for people and animals to live on.

Scientists have been able to piece together a picture of the Earth's climate dating back decades to millions of years ago by analyzing things such as ice cores, boreholes, tree rings, glacier lengths, pollen remains, and ocean sediments, and by studying changes in the Earth's orbit around the sun.

So what's the problem?

As humans emit more greenhouse gases into the atmosphere, the greenhouse effect becomes stronger. More heat is trapped, and the Earth's climate begins to change unnaturally. Since the industrial revolution, which began in the 18th century, the amount of carbon dioxide (CO2) in the atmosphere has increased by 35 per cent. In fact, the concentration of CO2 is now higher than at any point in the past 650,000 years.

Usually the increase is a very gradual affair which allows time for nature to adapt. The worry about the present global warming is that it is happening much faster than usual and will result in catastrophic changes in the environment.

Is it our fault?

Few people now dispute that global warming is taking place but some argue that humans are not the main cause of the warming and that it is due to natural variation. If that is indeed the case it would imply that we cannot do anything to alter the warming.

But if humans are either causing or increasing the rate of warming then decreasing carbon emissions and looking for alternative sources of energy makes sense.

Related links