17 April 2019

I tracked down someone who’d get us to the answer: greenhouse gas footprinting expert Mike Berners-Lee. Climate impact calculations are just the sort of thing he does for work at Small World Consulting at Lancaster University in the United Kingdom. And estimating the impact of a text message is exactly the thing he did for his 2010 book How Bad Are Bananas? The Carbon Footprint Of Everything. A carbon footprint, he explains, is a way of estimating the total climate change impact of something you do or buy — all along the supply chain, from manufacturing to delivery to use — with a metric called carbon dioxide equivalent, or CO2e, which translates all the different greenhouse gases into a comparable amount of CO2 by impact. Berners-Lee walks us through the impact of a text message, how it compares to emails and regular mail — and what happens if a text message itself is a heated one. The interview has been edited for length and clarity.

I’m finding myself speaking to the pages of my own book, which is a slightly strange experience. The book lists all these carbon footprints in order of magnitude, from very small to very large. The largest was burning all the world’s fossil fuels. And the smallest, the very first item in the book, is the carbon footprint of a text message. This is a little out of date, about five years ago. The technology has changed, somewhat — not massively, but somewhat — and the estimate I made at the time was 0.014 grams of CO2e. Now for perspective, the average U.K. person has a carbon footprint of about 15 tons a year, which is something like 35 kilograms a day. So 0.014 grams is a very small amount. We’re talking about a very big number against a very, very, very small number. So it’s tiny. All carbon footprints are about bang for buck. So it’s: How much does text messaging do for our lives? Against: What’s the impact? When we wrote this a few years ago, we estimated the carbon footprint of all the world’s text messages to be 32,000 tons of CO2e per year. By now, it will have grown quite a bit, but 32,000 tons is still a tiny figure for all the world’s text messaging.

Just think of what text messaging does. It’s the way that I keep in contact with my kids when they go out at night. … There are whole communities in developing countries, where people are in contact with their friends, relatives, colleagues and so on — through text, in a way which they would not otherwise be in contact at all. We took into consideration the energy used by both the sending phone and the receiving phone, and a proportion for the embodied carbon in the manufacture of the phone, which is a bit of an unknown because you have to make an estimate about how many text messages that phone is going to (handle) over its lifetime. And also the network. In that sense, if we do what the reader asked us to do and set us aside the carbon footprint of manufacture and transport of the device, so that’s an even smaller portion of that already tiny amount. It’s really tiny. The other thing about texts is that they’re so simple and basic, aren’t they, all you’re doing is transmitting a very simple message, you’re not even putting any fonts on it or anything. But the minute you start doing things like, “Oh, I’ll send a photograph while I’m at it,” that dramatically changes it. Suddenly you’re sending a lot more data — up goes the footprint.

If you read it on a computer screen, then your computer is using energy all the time that you’re staring at the screen. If it’s a spam email, it’s actually got a smaller carbon footprint because chances are, it gets put in a spam folder and no human being ever wastes any time on it. But if it’s got a long, tiresome attachment on it, then it gets a lot bigger as well, just because the size of it is bigger. The estimate we made for an email was about 4 grams (of CO2e). So we’re comparing 4 grams for an email and 0.014 grams for a text message, so we’re talking about a factor of 300 between the two.

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