Dear Readers, this week I have been looking into the vexed question of the carbon footprint: what it is, the different ways in which we can look at it, and the ways in which we can compare countries and individuals. In a few weeks I’ll be doing my own carbon footprint calculation and no doubt I’ll be sharing the results with you, and trying to decide what the best ways to reduce it are. But firstly, as with ‘sustainability’, it’s become a bit of a difficult thing to assess.

The formal definition of the carbon footprint from my OU textbook is ‘the annual amount of greenhouse gas emissions (mainly carbon dioxide) that result form the activities of an individual or a group of people, especially from their use of energy and transport and consumption of food, goods and services’.

However, as you might expect this simple definition runs into a few problems when we look at the real-life statistics. Firstly, sometimes they’re expressed as carbon, sometimes as carbon dioxide, and sometimes as ‘carbon equivalents’ – this last definition includes gases such as methane and nitrous oxide, which although emitted in much lower amounts are extremely potent greenhouse gases – one tonne of methane (from belching cows, waste, manure spreading and decomposition) equals 21 tonnes of carbon dioxide, while one tonne of nitrous oxide (mainly from nitrogen fertilisers and industrial processes) equals a stonking 310 tonnes of carbon dioxide. One big problem with the melting of the permafrost is that the resultant exposed vegetation is releasing vast volumes of methane. But, I digress, as usual.

A further complication with the footprint idea is ‘where are the boundaries?’ Some footprints are only concerned with the direct emissions of a household: this comes down the fossil fuels that are burned by our cars and the public transport that we use (especially air travel), and that we use to heat our homes and power our appliances, and is known as the Production Perspective. Everything else: the carbon that is used in the transportation of our food and the import and creation of our clothes, our waste services and our schools and administration, are rolled into the carbon footprint of the sectors that produce them. By this measure, UK households are responsible for only about 20% of the greenhouse gas emissions of the country.

However, if you do include these indirect carbon costs, something called the Consumption perspective, things look very different. While some 10-20% of carbon emissions are still thought to be out of the control of the consumer, the rest is down to the individual choices that are made.

There are a couple of problems with making these choices, however. The first is that, clearly, the information to make good choices is often sadly lacking. How do we know how damaging it is when we purchase a punnet of British strawberries in April when they are local but out of season (and probably grown in a heated polytunnel) compared with a Spanish strawberry which has been freighted but probably grew outside? There is no consistent, accepted method of weighing up the carbon values of the goods and services that we consume, and most of the time, although we can try to buy local and seasonal, and to ask questions, we really have no clear idea.

The second issue is that not all consumers in a society are created equal. In the UK, the top 10% of wage earners have a carbon footprint more than three times the size of the poorest 10% – they take more holidays abroad, they have more and bigger cars, they have bigger homes to heat and they generally have more money to spend on consumer goods. I can’t help thinking that a campaign aimed at richer people who actually have the money to make changes might be worth doing.

It’s very important, when looking at global carbon footprint figures, to look at the carbon emissions per head of population, too. While the absolute figures for China, for example, are staggering (in 2015 they emitted 9680 million tonnes per year, nearly twice what the US, the second biggest emitter, managed), in terms of population they are somewhere in the middle of the list of countries, with a Chinese person having a carbon footprint of 7.5 tonnes, while someone in the US has a footprint of 17 tonnes.

There is no doubt that countries such as China and India are in a race to catch up with the likes of the US: they want the same standard of living for their people, the same level of industrialisation, and the possibility of economic stability and growth. There is also no doubt that the planet cannot survive if everyone has the same emissions as the average American or Briton.

This is why climate change, like most things, is a social justice issue. We cannot expect other countries to halt their development while those of the industrialised countries continue to grow. We cannot tell the poor farmer in Uganda (average carbon footprint 0.1 tonnes of carbon dioxide per year) that he cannot buy a tractor or a car. But we do need to look at what can be done to reduce the emissions of the richest countries in the world, and I suspect that, as yet, we have no idea of what changes to our lives that might involve. No one is talking much about the end of the petrol-driven car, the rationing of air traffic or the changes to household heating that might be needed. And we need to share technologies with the developing countries such as India and China so that they don’t follow the same fossil-fuel heavy route that we have. Will these things happen? Only time will tell, but I do fear that we are in a world of adaptation to what’s going to come, rather than prevention.