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Reducing our digital carbon footprint

Digital publishing has a much larger carbon footprint than many might imagine. John Barnes looks at what we can all do to reduce it.

By John Barnes

Reducing our digital carbon footprint
“Total energy usage for the world’s data centres in 2022 was 416.2 terawatt hours.”

The climate has rapidly moved to the forefront of global consciousness in the last few years. Excessive heat waves, sea level rises, devasting wildfires and demonstrations by activists, such as Extinction Rebellion and Just Stop Oil, all serve to highlight the climate crisis and focus on the need to take more stringent and urgent action.

We are bombarded with many sobering statistics about the impact a high carbon economy has on the planet, and, increasingly, how internet services and tools are significant contributors to this problem.

Total energy usage for the world’s data centres in 2022 was 416.2 terawatt hours, significantly higher than the UK’s total consumption of 300 terawatt hours (Source: The Independent). On top of this, internet usage makes up 4% of global CO2 emissions per annum or the equivalent of all the world’s air traffic, which is seen in its own right as a significant contributor to the problem (Source: Global e-Sustainability Initiative (GeSI)).

Whilst these macro examples of use are very notable, looking at the details in some ways is much more alarming. The median desktop page transfer size has grown from 1.4MB in 2018 to 2.2MB for desktop sites and 2MB for mobile sites in 2022, primarily due to the increased use of hi-res images and video (Source: HTTP Archive). Social media use also contributes significantly to growing carbon use, as a single user spending five minutes a day on social media uses 20kg of carbon per annum, or the equivalent of driving a car 52.5 miles (Source:

New technologies such as generative AI also speed up energy use in large data centres, that not only need energy to process and transmit data, but also water and electricity to cool down servers and chips. A recent study by researchers at the University of California, Riverside, revealed the significant water footprint of AI models like ChatGPT-3 and 4. The study reported that Microsoft used approximately 700,000 litres of water during training of GPT-3 in its data centres. More significantly, day to day use of generative AI tools like ChatGPT in answering questions, or generating text, also use significant energy and cooling at data centres. For a simple conversation of 20-50 questions, ChatGPT consumes the equivalent of a 500ml bottle of water!

This has prompted individuals and industries alike to evaluate their environmental impact. As the digital landscape increasingly intertwines with our everyday lives, the need to minimise our digital carbon footprint becomes increasingly more pressing.

Analysis of data centres has been an agenda topic for technology journalists for some time. One of the first notable articles was written by the Guardian in 2015, with the thought provoking headline, ‘How viral cat videos are warming the planet’.

Thinking at the time was that the transfer of data was the biggest contributor to energy use at 72%, with only 20% for computing and a meagre 4% for storage. By 2020, that view had changed, and in a study by The Carbon Brief entitled ‘Factcheck: What is the carbon footprint of streaming video on Netflix’, transfer had reduced to 29% and computing and storage had both significantly increased to 57% and 13% respectively.

All media owners are grappling with this issue and most have set up groups to review and manage the reduction of carbon footprints. Trade bodies like FIPP and the PPA both have sustainability groups and have set up strategic relationships with independent bodies and auditors who can help measure the size of the problem and devise strategies for media owners to reduce their footprint.

Most are using the Greenhouse Gas (GHG) Protocol which provides standards, guidance, tools and training for business and government to measure and manage climate-warming emissions. Typically, the top two categories in media companies for this GHG audit are ‘purchased goods and services’ (the biggest type being venue and accommodation hire and collateral such as printed brochures etc) and ‘use of sold products’ (typically websites and printing production operations).

When looking specifically at website operations, William Reed has adopted the Measure, Optimise, Deploy and Educate (MODE) strategy developed by hosting partner

The ‘MODE’ approach starts with measurement. The GHG methodology, measures carbon based on spend (ie. costs for hosting will be assessed and carbon calculated based on this), which is a recognised top-down approach. However, it is also important to look at the issue from the bottom up (ie. page level) and get a sense of what typical pages emit. There are many free tools that can be used for this such as Google Lighthouse, as well as paid application performance monitoring (APM) tools such as Datadog or

A very simple and quick way to get a useful snapshot is to use a tool on the website.

Website construction

When considering digital sustainability, it is essential to look at how websites are constructed. Like a physical building, a website built with robust and efficient materials will perform better and be more sustainable. The foundations of a low carbon website start with a lean, effective digital architecture. Utilising technologies that facilitate the production of pages in a less resource intensive manner is key.

For instance, switching to static HTML, where possible, can make a significant difference. While JavaScript can add considerable functionality and dynamism to a website, excessive use can add unnecessary page weight and increase energy consumption, as it demands more processing power from the server and end user device.

However, website sustainability extends far beyond layout and design, and when moving into the ‘Optimise’ part of ‘MODE’, it is essential that an all-encompassing approach is adopted. This involves evaluating third party scripts, reducing the reliance on bloated digital assets and making sure code is lean and up to date. Out of date plugins or applications will slow the site down, as it may take longer to call the application into the page, or may fail because it is not available. This will use more energy.

Typically, heavy images are a key contributor, and one of the more difficult aspects to understand. In the print world, a mechanical data sheet would state the maximum weight for an insert because the weight of the insert will impact the postage and distribution costs, as it will make the magazine heavier and the postage more expensive.

Most people understand this, but don’t realise that pictures styled in Photoshop could unintentionally be 10 or 15 times heavier. William Reed has been using tools like to illustrate this, as it translates carbon into understandable comparisons such as how many miles you could drive in a fully charged electric car, how many trees you would need to plant to offset the carbon used and, the one that seems to resonate the most, how many cups of tea you could make. Using tools to help compress picture weights is also a very effective way to deploy such best practice, and constantly measuring sites and feeding back improvements to internal stakeholders is key.

Hosting choices

When using the ‘Optimise’ part of ‘MODE’, where websites are hosted has a big impact on carbon footprints. This doesn’t necessarily mean that there are good or bad locations, it means where they are located will be linked to their economic development in terms of the way energy is created, and this will impact how much carbon is being used by hosting centres. Obviously, very sustainable renewable energies like wind or hydroelectric are going to have a lower carbon footprint than coal. But this can be hyper local, as different American states have very different energy footprints, because the way energy is created. A state like Texas could, therefore, have a totally different carbon footprint to a state like California.

It is also important to note that generalisations cannot be made; the specifics need to be examined. As an example, it is meaningless to say that hosting in a so called ‘dirty’ country or region is worse that hosting in a ‘cleaner’ one. If a data centre is constructed in the right way, is efficient and well optimised, it could be more efficient than a poorly constructed, inefficient and older site in a greener location.

A good checkpoint for this is a site called, which visualises carbon intensity, low carbon, and renewable status. In addition, hosting companies will have tools and dashboards available to allow constant monitoring of these KPIs.

Educating staff and end-users

The ‘Educate’ part of ‘MODE’ is really the most important part because when you are measuring carbon top down, or even bottom up in the ways described, the end user as well as staff need to be factored into the equation. End users will have to charge phones and will do so more frequently if pages they use are not optimised, they will have different connection speeds, may or may not have certain tools installed, and could have slower out of date browsers.

In our journey towards digital sustainability, it is essential to remember the role of end users. Educating users about the importance of reducing their carbon footprint is every bit as important as reducing our own. Increasingly, this involves evaluating the need for features such as ‘print page’, and, if required, how this can be best optimised to use fewer pages and be better formatted, rather than printing through the browser and maybe using four or five pages that are unformatted. Effective education sees internal and external users as all part of the process.

So, what is a realistic CO2 target for a well optimised page? Sadly, there is no universally agreed target as it can depend on a specific website, which national markets it is serving, its audience size and make up, and, of course, the technology used.

A low carbon website could have a carbon footprint of less than 100g CO2 per page, whereas a high carbon site will have a footprint of more than 1000g CO2 per page. The British government has set a target of reducing the carbon footprint of UK hosted sites to zero by 2033.

If selling data subscriptions to do real time modelling with graphs and charts is the business focus, the carbon footprint clearly cannot go below a certain level. Equally, it may need to be significantly higher than a site that’s just optimised for reading with few pictures, or a site that’s streaming lots of videos versus a site that’s doing real time networking with people. Understanding the differences between websites is also part of understanding the way different carbon levels for different kinds of businesses means there is no one-size-fits-all target. Simplistically, the best approach must be to be as low as possible, continuously measured and improved and a significant KPI.

This challenge highlights the importance of a co-operative approach with other media owners. Sharing ideas and learning from one another’s experiences is vital to progress in this area. We must be open to the fact that we can’t know everything, and even if five out of ten things are being done well, there might be other elements that one media owner hasn’t considered, and another has. By fostering a culture of knowledge exchange, we can collectively improve our digital sustainability practices.

Digital sustainability goes far beyond reducing a website’s carbon footprint. It involves an all-encompassing approach that includes the choice of technology, the optimisation of digital assets, careful selection of hosting and distribution partners, and consideration of the end user’s role in the carbon equation. It is about striving for continuous improvement, fostering a culture of collaboration, and viewing sustainability as a shared responsibility. In this digital era, each of us from content creators and website developers to end users, has a role to play in making the digital world a more sustainable place.

MODE Checklist


  • Work with a trusted partner using the GHG Protocol.
  • Use free tools like Google Lighthouse or APMs like Datadog to measure performance and identify improvements.
  • Get quick snapshots for free from sites like


  • Optimise images / videos by compressing them and using appropriate file formats.
  • Minimise use of heavy JavaScript and CSS.
  • Reduce the number of third-party scripts being used.
  • Use more efficient libraries, frameworks and technologies.


  • Select a web hosting provider that uses renewable energy sources.
  • Use CDNs to serve static assets from servers close to the user.
  • Enable browser caching to reduce the number of requests made to the server.
  • Use server-side rendering to generate HTML on the server, rather than client side.


  • Educate staff to continuously improve and reduce the carbon footprint of websites.
  • Encourage users to reduce energy consumption by highlighting the impact of their actions.
  • Visualise the scale of the problem to grab attention and increase understanding.

John has created a resource sheet (Optimising digital operations for sustainability), which you can read here.

This article was first published in InPublishing magazine. If you would like to be added to the free mailing list to receive the magazine, please register here.