I don't agree with the reasoning presented.
It takes the estimate for the amount of energy that it takes to run the internet infrastructure and clients (141GW * 8765h in a year = 1235865 GWh), divides it by the amount of data transferred yearly (241 billion GB) and gets to 5.12kWh/GB.
You might argue that if people download more data, more equipment needs to run to enable it, but really all this energy consumption is happening regardless of my PC being idle or saturating its fiber pipes with torrents. If your website weights 14kb, all this same equipment needs to be on for my PC to load it.
The website usage on the client side is more to do with resource usage. Unnecessary usage of Javascript is often what makes websites laggy.
You computer will normally down-clock (you can turn this off in the bios) when under lighter loads.The difference between a JS-free webpage and a bloated web page that uses multiple JavaScript with extra Javascript for ads and tracking could be around 10W/H to 40W/H on Desktops.
Maybe, or maybe the new equipment is much more efficient than the one it's replacing. It sounds true, but you can't really tell if it is or not, and really my annoyance is in saying it costs any estimated amount of energy, or carbon, to transfer 1GB of data. It does not, the transfer itself is basically cost-less. What costs money is running the infrastructure that makes it possible, and that's much harder to measure.
What matters is the marginal consumption. It should be really small. Averages don't mean much. I can download one GB of Data for almost free, I doubt I would burn 3 kg of CO2 doing that
