This page is an early draft for a primary audience. It needs developing for a young adult audience.
[NB this ‘page’ to linkto/contain videos 1A, and possibly 2V from DAS’s top list]
The Earth is surrounded by a blanket of gases – the atmosphere. Some of the gases are known as ‘greenhouse gases’ – these include water vapour, carbon dioxide, methane and ozone.
The greenhouse gases in our atmosphere interact with radiation from our sun. They trap it – once it’s in, they stop some of it escaping back out into space. In other words, they do what their name suggests – they help to keep the planet warm. It would be nice to say this works like a greenhouse, but scientists hate the term ‘greenhouse effect’ – you can read on to find out why, or skip to the next bit. [‘why’ bit could be a pop-up box? with alternative link to ‘next bit’ i.e. after pop-up]
The reason goes back to basic science. There are three ways heat can move.
A greenhouse’s glass lets the solar radiation through. It heats up the air inside the greenhouse, and the hot air tries to escape by convection – but the glass stops this from happening.
Greenhouse gases let the solar radiation through, but they encourage warming by stopping the radiation escaping back into space; not by preventing convection. So although the processes are broadly similar, many climate scientists hate this analogy. Back to the greenhouse effect. [pop-up box, if there is one, ends here]
Observations of the planet’s temperature tell us the Earth would be about 30oC cooler if we had no greenhouse gases. In other words, the Earth would be too cold to support life.
[NB could use some of Dave’s talk/slides here too; keeping the concepts clear. Dave: We can certainly get some images for this.]