The greenhouse effect [in dev]


isn’t climate
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.
1: by conduction, like the heat in a griddle warming the food you put on it;
2: by convection, like the heat in an oven moving with the air – warm air rises through convection and that is why it is always hotter at the top of the oven;
3: by radiation, like the heat from the sun.

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.
[Dave:  This feels great for primary. For YA I’d like to add in something about the difference between long wave and short wave radiation. And about molecules of GHG absorbing the longwave and re-emitting it, still as long wave radiation, but in all directions. So some of the energy that was leaving the surface/lower atmosphere is remitted back to the surface.

[NB could use some of Dave’s talk/slides here too; keeping the concepts clear. Dave: We can certainly get some images for this.]