During a normal working day, you will probably send emails, do at least a couple of online searches, send countless messages on WhatsApp, and take part in one or two video conferences. Later, in your free time, you use social media, visit some informational sites, listen to streaming music, and watch movies or TV series on Netflix or other platforms. At first glance, these all appear to be sustainable behaviours. After all, compared to the past, we avoided wasting paper for letters or newspapers, and we also eliminated the use of plastic for CDs and DVDs. Moving in the digital, and therefore immaterial, world of the Internet gives the impression of having zero impact on the environment. In reality, things are very different. Behind ethereal terms such as "cloud" lies the much more commonplace reality of the physical infrastructure of the Internet, made of endless cables, colossal data centres, routers, switches and everything you need to bring the Internet to (almost) the entire world.

The staggering amount of energy needed to power the infrastructure and use of the Internet leads to more "digital pollution". The entire ecosystem that revolves around the Web, including the devices used to navigate it, causes 3.7% of our planet’s total greenhouse gas emissions. This is greater than the amount of gas emissions generated by the airline industry. Just the data centres where our emails, social media posts, and bank, company or institutional data (and much more) are stored consume something like 200 terawatt hours per year, just under 1% of all energy consumed globally. Although a single email consumes very little (about 4 grams of CO₂  if there are no attachments), this small sum must be multiplied for the more than 300 billion emails that are sent and received every day all over the world. The same is true for the 3.5 billion daily Google searches, and in general for all the more trivial activities carried out by 4.1 billion Internet users (53.6% of the population), which in the Western and developed world are each responsible for producing around 80 kilos of greenhouse gases per year.

It is difficult to be surprised by these estimates, given that according to some calculations the normal office worker receives  121 emails per day, including newsletters, spam, emails they are copied on, and question and answer emails between colleagues. Furthermore, some of these certainly contain images, increasing the amount of emissions generated by the emails to 50 grams each. The result? The most active email users can create 1.6 kilograms of CO₂ every day, just through using email. The situation is more or less the same for other instant communication tools: a single tweet generates 0.2 grams of greenhouse emissions, while messages sent via WhatsApp or Messenger have a slightly higher impact than emails, although their frequency is much higher. Obviously, the quantity of attachments, photos and even emojis sent also plays an important role.

On balance, only the old-fashioned SMS, which consumes 0.014 grams of CO₂, has a truly reduced environmental footprint, but it is dying out in everyday use. If this how much is being consumed for simple text messages, it is almost superfluous to point out the impact of the increased use of video calls and videoconferencing, in which data transported from one part of the globe to another increases exponentially. An afternoon-long videoconference whose participants are located in different countries could produce up to 215 kilograms of CO₂ alone. However, there is one element to take into consideration, especially during the pandemic: we have fully understood that some of the meetings that we would have normally held in person can instead be replaced by tools such as Zoom or Skype. Although the energy consumption of videoconferencing is high, using these software programs to replace travel by car, train or plane means saving on average 93% of emissions.

It is not, however, the messages, emails and videoconferencing that cause the bulk of the ICT environmental footprint. To date, video streaming alone represents 60% of the total traffic of data traveling on the Internet, generating over 300 million tonnes of greenhouse gases every year. By themselves, videos account for 1% of global emissions and consume the same amount of energy as a nation like Spain. Platforms hosting films and TV series, videos on social networks, sites like YouTube and adult entertainment platforms combined generate pollution levels that continue to climb year after year as the quality and definition of the videos increase, as therefore does the amount of data to be moved from one part of the globe to another. The reduced use of plastic and the absence of pollution caused by the distribution of physical DVDs is not enough to make the entertainment industry sustainable. The same goes for the music industry, as well: music streaming is responsible for around 300,000 tonnes of CO₂ per year in the United States alone. It is even estimated that if you listen to the same album more than 27 times in your life, it is more sustainable to buy a CD than to stream the record.

The way forward passes through what the NGO Shift Project calls “digital sobriety”.  First of all, companies that operate on the Internet, and especially the Web, should strive to make their products more efficient. It is calculated, for example, that giving those who are listening to music on YouTube the option to not view the videos would reduce emissions caused by the streaming platform by 5%, equal to 11 million tonnes of emissions every year. Likewise, Facebook could significantly reduce its energy consumption by preventing promotional videos from starting automatically. Similarly, Netflix could encourage its users to not always watch films or TV series in high definition, significantly reducing data traffic and therefore the energy needed to power the platform. Even more important, however, is to increase the lifecycle of our technological devices.

Changing smartphones every three years instead of every two has a huge positive impact on the planet, because it saves the precious minerals used in its production and all the energy necessary to produce and distribute it around the world. The same obviously also applies to personal computers – replacing computers every six years, compared to an average of only four today, would save 190 kilograms of CO₂ emissions per person. Each of these individual behaviours may seem irrelevant, but if we all adopt them together it can make a difference. Similarly, it may seem like a trivial matter to use our car less or to separate our own waste. Therefore, to protect the environment it would help to adopt certain prudent practices: use links instead of attachments, send fewer pointless WhatsApp pictures, do not always use high definition on Netflix, disable videos on YouTube and change smartphones less frequently. The more time that passes, the more urgent it becomes to adopt these behaviours. Over time, the relationship between technology and pollution has only become worse. By 2025, digital emissions will double, reaching 7%. It is estimated that around 2040 they will reach 14% of global emissions, slightly less than the energy consumed by all of the US. If we want to prevent our use of the Internet from further contributing to the climate crisis, the way forward must be digital sobriety.