I have had people say to me on many occasions “if they cannot predict tomorrows weather how can they predict climate change”.

This is a common misconception that climate and weather are the same thing.

Think about heating up some water. As you heat it the temperature increase will not be uniform. The warmer water will rise to the top cool and drop down again in a process called convection. As you have probably noticed and you can see in the image, as it does so it does not move in a straight line but produces a lot of eddies and swirls.

Even with a very powerful computer it is impossible to predict the movement of the eddies and swirls for more than a very short period of time – it is a very complicated, chaotic system.

However, what we do know for sure is that for every 4.1813 Joules of energy that is put into the system per gram of water the average temperature rise will be 1°C. As with many things we do not have to know all the details of what is going on in individual parts of the system to know what is happening to the whole system.