What on earth is a carbon footprint? 

Nearly everything we make or do takes energy – and at present most of our energy comes from fossil fuels (gas, oil, or coal).  When fossil fuels burn, they release carbon dioxide.  Your ‘carbon footprint’ represents all the carbon dioxide generated in  providing the things you use, and the life you live. It’s expressed in kg of CO2e, that is, kilogrammes of carbon dioxide equivalent.

Most homes are heated by fossil fuels.  Most cars and trucks burn fossil fuels.  Heating, travel, waste disposal, services (schools, gyms, hospitals), making things and getting them to us, all contribute to our carbon footprint.   Energy produced from renewable sources (solar, wind, tides) has a much lower carbon footprint than fossil fuels.

What’s wrong with carbon dioxide?

Nothing!! In moderation.  Plants need carbon dioxide.  They take it in and, using sunshine, turn it into plant tissue.  Then they die, they rot, and the carbon that was in the plant gets released as carbon dioxide.  This is the carbon cycle we learnt about at school.

The trouble is – carbon dioxide acts as a ‘greenhouse gas’ – like glass, it lets sunlight through, but is less good at letting heat pass. When sunlight hits the earth it heats it.  And the carbon dioxide helps to trap some of that heat. Carbon dioxide levels in our atmosphere have risen a lot in the last hundred years, and so the world has got warmer. It’s as if we’ve put a duvet over the world.

Isn’t it great that we’re getting warmer?

Well, maybe it seems so, here in the UK.  But a hotter world means more storms; more heatwaves, and changes in weather so some places that used to grow good crops now suffer drought and famine…. And as the polar ice melts, sea levels are rising. Many coastal cities and islands will flood. Food shortages, storms, and flooded cities – that really will affect us all.

How come carbon dioxide levels are rising?

It’s fossil fuels that are the problem.   They represent millions of years of stored carbon dioxide, in plant material which rotted down and became coal, oil or gas.  And we’ve been burning that stored carbon in only a few decades. The balance has been broken.  Plants are working as hard as they can using the sun to fix carbon. They can’t keep up – and since most of the land surface is already covered in plants, even planting more trees won’t be enough to restore the balance.

Footnote 1: ‘Territorial’ versus ‘Consumption-based’ footprints

The footprint shown here is ‘consumption-based’. It aims to account for the total impact of how we live on the world’s carbon dioxide emissions. We think that’s really useful in helping us decide what to do, so that’s what we report here.  It is also possible to calculate footprints for an area, based solely on what happens locally. The UK carbon footprint published by government is often of this type, and so ignores the huge footprint of all the stuff we import. 

Footnote 2: Other greenhouse gases

There are other greenhouse gases in the atmosphere which have a similar effect to carbon dioxide, for example methane and nitrous oxide. Emissions of these have also been rising due to human activity.  Carbon footprints include the effects of these gases, which is why they are expressed in kg of CO2e (e for ‘equivalent’).  Climate action plans address ways to cut these emissions too.