BBC One Planet's annual emissions as a tower of 10-tonne cubes (actual volume of gas).

BBC One Planet's annual emissions as a pile of 1 tonne cubes of gas.

BBC One Planet's annual carbon footprint as a sphere of carbon dioxide gas.

BBC One Planet's average daily carbon footprint (actual volume).

BBC One Planet's average emissions per second. Visualising rates of emission on very small timescales, as here, allows viewers to see the emissions as dynamic.

The One Planet radio programme on the BBC's World Service came to Carbon Visuals with simple question: "what does our carbon footprint look like?"

One Planet was carefully accounting for emissions arising from the making of the programme and had arrived at a figure of about 34.9 tonnes per year. But what does that mean?

Measuring carbon dioxide in terms of mass (tonnes) makes sense from an accounting point of view but doesn't give us a sense of scale we can relate to. We examined a variety of alternative ways of representing One Planet's footprint.

We have shown the programme's annual emissions by volume in a recognisable location and in relation to an iconic feature - Trafalgar Square and Nelson's Column. These provide a sense of scale that enable the viewer to relate to the volume.

You can hear a discussion about this project, first broadcast on Thursday 8 April 2010, by visiting the One Planet website.