One of the biggest issues in driving or supporting improvement of any kind is how to measure both the current and future state. If you do not know where you are starting, or what level of improvement is required, it is extremely hard to know what to do. This is one reason why the first stage in Amazon’s Climate Pledge is for signatories to start measuring their carbon footprint.[1]

However, committing to measurement, and actually being able to measure, are two completely different things. There is not very much information available to help organisations to measure their carbon footprint, especially not of cloud computing. As a small step to support this activity, we have therefore been developing a cloud computing carbon footprint index for Purple Dragons.

At present, the Purple Dragons Cloud Computing Carbon Footprint Index contains four key criteria:

The result from the Website Carbon Calculator[2]

The Website Carbon Calculator uses five sources of data to assess a website’s carbon footprint, including website-specific values for data transfer over the wire, energy source, and website traffic, and average values for two other factors. It gives two results: the relative cleanness of the site compared with ‘other websites’, and the grammes of carbon produced each time someone visits the website. We use the grammes of carbon dioxide produced per visit to give a value from 1 to 10, where 10 means no carbon dioxide, and 1 is ten or more grammes. A lower carbon footprint therefore gives a higher figure for the index. This factor has a weight of 0.25 in the overall calculation of the Purple Dragons index.

The energy or sustainability policy

This factor assesses whether the company has an energy or sustainability policy. We search for any evidence of an energy policy report, and also look at the website for more information about any policy on green energy or sustainability. The possible values for this factor are from 1 to 10, where 1 indicates that there is no evidence of an energy policy, and 10 means the publication of an energy report.

Ethics and renewable energy use

The third criteria is the company’s use of renewable or clean energy. We give a value of 0 for no use of renewable energy (or no evidence of that use) and 10 for clear evidence of full commitment to and use of renewable energy. We find this information by searching for any ethical report or anything mentioning the use of renewable energy or the company’s general ethical stance on energy.

Messaging on social media

You can learn a lot about a company from its messaging on social media. We look at the url of any blog pages, key words from the company’s blog coverage, the Twitter handle, and also key hashtags from the Twitter account. We use this to build up a picture of the messaging on the company’s ethical stance and approach to its carbon footprint. A score of 1 means very low messaging, and a score of 10 means active messaging on these subjects.

Bringing the index together

These four items are then summed, with a weight of 25% for each item, to give an overall index. The possible values range from 4 to 40, with 40 being the best value.

Where next for the Purple Dragons Cloud Computing Carbon Footprint Index?

One thing is certain with any index of this kind: we and it cannot stay still. As the available information improves, so must the index. Both the quality of existing metrics, and indeed the metrics themselves, will be updated over time as new and better information becomes available.

In particular, it will be clear that the second, third and fourth criteria are currently not very quantitative or refined, and will need improvement. We plan to use the data gathered in the process of building this version of the index to inform future developments, and create a more quantitative and objective measurement. We may also add other data items as these become available, and update the weightings to reflect aspects that are more important in determining the carbon footprint of cloud computing.

The aim is to create a state-of-the-art index that will give the most accurate picture of the carbon footprint of cloud computing. It is very much a matter of ‘watch this space’—and ongoing development of both ideas and information.



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