Carbon Calculator Systems

If sustainability is important we need to be able to measure it. Unfortunately the notion is often used very loosely to cover a wide range of concerns, each measured in a different way, with different units. You cannot simply add everything up.

For reasons given elsewhere, I and many others have concluded that most serious environmental problems correlate strongly with greenhouse gas emissions (GHGE) provided that all gases are included and are given appropriate equivalent 'forcing' values. These emissions can be accurately measured, and crucially, you can add them up. They can therefore be used as an averaging indicator for a wide range of physical environmental trends.

The resulting 'carbon footprints' are useful and versatile. I and many colleagues have developed a substantial 'stable' of calculator systems for measuring carbon emissions of individuals, households, organisations, business enterprises and events. These are usually spreadsheet-based, so a user simply has to answer questions or enter numbers and the results are calculated automatically. The programmes are usually in Excel, so are accessible and easy to download. In addition, the underlying formulae are transparent and readily inspected.

Much of the development was managed in conjunction with the Open University, which used a bespoke version of the calculator as part of its environment degree course.

Most effort has gone into ‘personal’ calculators like the one used by the Open University. We decided to adopt a ‘comprehensive’ approach that covered all greenhouse gases and all emissions that an individual might be considered ultimately responsible for. This includes emissions embodied in goods, services and imports, and in the services provided by public bodies. This is therefore a ‘consumption-based’ approach that uses categories that make sense to consumers, different from the usual government breakdown into industrial sectors. A general overview is in

Designing a carbon calculator 2020

One advantage of the comprehensive approach is that it exactly mirrors the national situation. A personal footprint is exactly one sixty-eight millionth of the national footprint, and the average value for subcategories can be derived from published national statistics. At the start it is assumed that a person is ‘average’ in all respects, then the various subcategories can be tweaked through questions and data inputs.

The result of such tweaks is a unique pattern that we call a ‘fingerprint’. You can see an example of this ‘fingerprint’ approach on the right. There are seven colour-coded consumption categories, in roughly rainbow-order. The ‘red end’ is for direct emissions that you can actually measure. The ‘blue end’ is for indirect emissions harder to measure. Black is emissions from governemnt and public services.

Example of a personal calculator spreadsheet (2014)

Quantitative carbon analysis  can be applied in many other ways, and for several years we measured emissions associated with one of the UK's most environmentally-conscious festivals, showing yearly transformations of both footprint and fingerprints, guided in part by the results. We developed a simple methodology for ‘standardising’ the footprint, so that one festival could be compared with another, or with itself in previous years. One big result was the understanding that festivals are an ultra-low-carbon form of holiday, usually better even than staying at home! Here is a report for 2012:

Shambala Festival 2012 Report (doc)

Other calculators have been devised for institutions. Here is an example, for rural museums:. You will see it can get quite detailed, so in most cases we offer a ‘quick and dirty’ version that can generate a rough answer just sitting around the tea-room/boardroom table.

Rural Museums calculator 2007 (Spreadsheet)

WHAT HAVE WE LEARNED, AND HOW DIFFERENT ARE RECENT CALCULATORS?

Traditionally, personal carbon calculators are quite detailed and take a long time to complete. They might also entail rummaging in drawers for energy bills and MOT certificates. This is fine for students who are forced to do it all as part of their work, but we have observed over and over again that ordinary citizens quickly lose interest and fail to get to the end. Calculators are just too long!

But if you don’t ask all the necessary questions, you won’t get a credible answer. What to do?

Fortunately, having analysed hundreds of responses, we discovered that most data inputs don’t make much difference. You can get very close just by asking a handful of key questions. In particular, we found that the single largest determinant of a person’s footprint is expenditure, which is well represented by income, which (with a bit of chicanery) is determinable. This concurs with the results of various academic studies. We extended this result in what we like to call ‘the megaphone effect’, that is, when you plot household income against household emissions, you get a megaphone-shaped distribution. It is true that different households of the same income level have a range of footprints, but the range is much greater for wealthier households, that often use their wealth for larger houses, more stuff, more car travel and more aviation. Poor households simply cannot do this.

Paradoxically, we often found that people who thought of themselves as ‘green’ had higher than average footprints. They were better than their income peers, but worse than an average UK citizen. The simple explanation is that Greenies tend to be richer than average, and it needs very careful choices to get the footprint down.

So income is key. What else? We found that house occupancy, that is how many people in how big a house, made a difference, although it is somewhat confounded with income; flying, because it’s easy and cheap to go very far; and diet: vegans had a food footprint only a quarter that of gung-ho carnivores. So just four questions is usually enough to estimate a personal footprint within a tonne, the UK average being about 10 tonnes per year.

Another discovery was that the footprint was rather insensitive to the usual range of lifestyle measures and household technologies. True, an utterly dedicated household could insulate to the hilt, run the house at 16 degrees, go vegan, never fly, abjure a car, and install photovoltaic panels. And they could shave a few tonnes off their total. But this is very rare, and if the hypothetical family still had a high income, what would they do with all that spare money?

Gradually it dawned on us that the answer lay in a direction we had regarded as taboo: offsetting, that is, paying for things outside the household sphere. A household cannot decarbonise itself, but its supplies of energy and materials can be decarbonised. And a household could simultaneously reduce its expenditure on high-intensity items and invest in low, or even negative-intensity items, such as wind and solar farms, reforestation, even carbon sequestration. This can be remarkably cost-effective. If a negative tonne of carbon (‘negatonne’) costs even as much as £500, a one-off investment of £10,000 will deliver 20 negatonnes for twenty years, zeroing all but the most profligate of wealthy households.

It might be argued this is simply not fair — that wealthy households can simply buy their way to net zero, without making any other changes. I would argue back that it’s now too urgent for fairness, and that anyway it’s good for the rich to pay for the decarbonisation process, just what they should be doing. And in any case, the last fifty years have shown us that only a small minority of greenies are prepared to make serious lifestyle changes. We have no option but to bring in the big technology.

Even more cost effective are the massive-scale projects undertaken at government/industry level, where a negatonne probably costs less than £100. Progressive taxation is a way to make the rich pay more for this, and carbon taxes can help focus individual choices.

Such consideration have led to a ‘gamified’ version of the calculator where the ‘player’ has to get to zero (or below) using a combination of lifestyle changes, household investments, external investments, and national schemes achieved through political activity. It’s ever so quick. Give it a try.

Net-Zero Game 2023

I tested this out on a first-year university class. Here is the result:

Provisional Results of a Classroom Trial [docx, 2023]