How to cram the entire UK carbon economy onto a single page

Where do all of the UK’s greenhouse gas emissions come from? It sounds like such a simple question. After spending the last six months working with the Guardian in an attempt to answer it, I can confirm that it really, really isn’t.

When I first decided to map out the UK’s emissions back in 2008, I soon realised that the task was a tiny bit more complex than it first appeared. Many of the official government figures contradicted each other. The Department for Environment calculated transport emissions in a different way to the Department for Transport. The Department for Business, Economy and Regulatory Reform kept changing the way it measured domestic and commercial energy use. I soon found myself having to choose between different official statistics, and find increasingly elaborate ways to fit the various clashing numbers together into a sensible big picture.

Adding in international aviation and shipping (which until recently were excluded from the Government’s official emissions total) seemed relatively straightforward – but how to account for the extra climate impact of emissions released at high altitude? What about the fact that since 1990, the UK has shut down huge chunks of its manufacturing industries and now imports large quantities of goods from overseas? Any fair analysis of our nation’s carbon footprint has to look at our total consumption, not just the emissions that take place within our borders. A proportion of the smoke that belches from factory chimneys in China, India and Indonesia in truth belongs to us.

Then there’s the sticky matter of food. The greenhouse gas emissions from agriculture – particularly methane from livestock and nitrous oxide from chemical fertilisers - are still subject to intense research, and there’s much we still don’t understand. Early findings and best guesses have had to suffice here for now.

Then, of course, there’s been the fun of trying to calculate the interactions between all of these different factors and build them into a user-friendly tool. After wrestling with these challenges by myself for a year, I was delighted to start working with the Guardian web team in 2009; they not only scrutinised, double-checked and improved on my model, but also took on the daunting task of translating all this stuff into a whizzy working online tool.

This has been a pretty enormous piece of work – it is, we’re fairly sure, the most complex online carbon calculator in existence. It allows you, the user, to tinker with the UK’s electricity supply, consumption patterns, transport and energy use, and see the results played out in real time. You can try out different policies or changes in public behaviour, and see what impact they might have on our total carbon footprint. But it’s still not finished – it’s very much a work in progress, and we hope to keep updating and improving it over the coming months.

So please, have a play with the tool, and send us your feedback – was it easy to use? Did anything seem strange or surprise you? Has it changed your mind about any particular policies or climate change solutions? If you’re really interested, please check out the calculations, assumptions and data sources behind the model (which are all freely available online), and please do send us your questions or suggestions for improvements.

A tool only has value if it is used – so please do use it, and if you like it, spread the word!