The leaky bucket

How are the flow of energy we get from the Sun and the flow of energy the Earth loses to space, related to each other? A useful analogy is a leaky bucket.

Once you’ve watched the video above, think about what happens if you add some extra water to the bucket in one go, without changing the rate of flow from the tap. The level will slowly fall back to where it was originally. Similarly, if an event such as a forest fire, emits heat on the Earth’s surface, this heat will slowly be lost to space and the temperature of the Earth gradually falls to where it was originally. This is why it’s the greenhouse gases emitted by burning fossil fuels, rather than the heat itself, which causes climate change.

But, it’s not so simple. This is mainly because the Earth has an atmosphere, which also has an impact on the flow of energy to and from our planet.

The temperature of the Earth’s surface, and the atmosphere above it, are governed by the intricate exchange of energy between the different components of the climate system: atmosphere, cryosphere (glaciers, ice sheets or anything else involving frozen water), oceans and land.

If this exchange of energy, called the Earth’s radiation or energy budget, is in balance, the temperature of the Earth’s surface stays the same. However, if anything happens to tip the balance, the temperature will change, in much the same way as the level of water in the bucket changes in response to changes in the flow rate of water in from the tap and out through the hole.

In the next Step, we’ll look in more detail at the Earth’s energy or radiation budget.