Our methodology.

Our carbon data is validated by carbon expert Mike Berners-Lee.

Mike is a professor, researcher and author of “There is no Planet B”, “How Bad are bananas, the Carbon footprint of Everything” and “The Burning Question” . Mike has helped us to make sure our numbers are right. Want to look under the hood?

Carbon calculator methodology

The Pawprint Carbon Calculator expands on Small World Consulting's industry based carbon calculations. This takes the total emissions output of the UK, allocated by industries, and breaks it down for the average UK resident.

We split this footprint into four main buckets (Home, Travel, Diet, Other/Spending) which are then subdivided into numerous individual data points. These data points form a tree as deep as needed to represent the data. Each data point in the hierarchy holds an average carbon emission score which can be summed to the data point above. The overall breakdown is displayed to the user one level deep.

Each user is allocated the default scores for each data point. Each survey question then modifies the user’s score away from that average. These are applied as multipliers to the average score to indicate using more or less carbon than the average resident. Multipliers can be combined when factors allow e.g. both the efficiency of your vehicle and the miles driven affect your car usage score (see example below). Answers to questions can affect multiple data points and data points can be affected by different questions.

A system of blacklists are used to hide irrelevant questions from users e.g. vegetarians will not get challenges on eating less meat.

Calculation of multipliers

Multipliers are expressed as a deviation from the average: 2 indicates twice the average (all other factors being equal), 0.5 indicates half the average. This allows them to be combined - it is assumed the factors do not interact directly.

Example - car usage

How many miles do you travel in a vehicle per year?

Average is 3,517 miles per year. Possible answers and multipliers are:

  • 0-3,000 miles per year (assume 1,500) - multiplier is 1500/3717 = 0.43
  • 3,000-6,000 miles per year (assume 4,500) - 1.28
  • 6,000-9,000 miles per year (assume 7,500) - 2.13
  • 9,000-12,000 miles per year (assume 10,500) - 2.98

Example of combination of multipliers:

  • Average CO2e for car usage is 1,336 Kg
  • I drive 6,000-9000 miles per year so my multiplier is 2.13. However my car is more efficient than average and has a multiplier of 0.80.
  • Total CO2e is therefore 1,336 kg x 2.13 x 0.8 = 2,277 Kg CO2e

The importance of the information you give us

Although your Pawprint is calculated using this scientifically validated approach, we rely on the information you give us to ensure you receive the most accurate figures possible.

Ready to take the next step?

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