The internet causes around 5% of global carbon emmissions. It's invisible, and difficult to measure, so little gets done about it. But if you're a developer who wants to help. Check out: https://sustainablewebdesign.org/ Pretty much all the solutions to making a greener web would make the web better in general. - Send less data (efficient video, images, fonts, etc) - Make fewer requests - Use a CDN (the greenest one…
Something that almost the entire population uses all day is only using 5%? Sounds incredibly efficient. Repacking fonts to be smaller sounds about as useful as plugging a hand crank generator in to the power point.
For web developers that 5% is our responsibility, and we have the means to change it in ways many people cannot.
As for fonts — yes I'm sure it would make a big impact. Font files are a decent chunk of average page weight.