Many favour the focus on KwH per GB as the CO2eqv will vary based on location for instance:
"In France, where I live, producing 1 kilowatt.hour of electricity emits on average 55g of CO2 equivalent (it's much less than most other countries, e.g. Germany's electricity emits 440g eqCO2/kWh, and the US 450gCO2/kwh, but in return, we have nuclear waste buried underground for milleniums to come)." https://marmelab.com/blog/2020/09/21/web-developer-climate-change.html
A great tool for finding real-world equivalencies to emissions quantities is https://www.epa.gov/energy/greenhouse-gas-equivalencies-calculator.
The first four all follow the 'enter your URL', get a readout method:
France seems quite developed in this space; as well as GreenFrame, there's https://greenspector.com/en/home/, http://www.ecoindex.fr/, http://ecometer.org/, https://theshiftproject.org, GreenFrame.io & Marmelab. A great explanation of the difference in the French approach is described by Gauthier Roussilhe here.
DEFRA - ICT emission reduction analysis https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/997523/ict-annual-report-2019-20.pdf
One of the more developed models, by the French developers MarmeLab, it distinguishes between three CO2 origins: CPU, Network and Screen. So a [[Static Site Generators]] might have a lot less carbon in its delivery onliny, but the CPU build might be offset the gain if the build happens frequently (MarmeLab do a good comparison of the two here). More info.
An advantage of GreenFrame is it can help you design systems that minimise footprint in the areas outside of control (screen, network to an extent) and focus on what can be controlled – CPU/server end. In the analysis above they found the screen was responsible for 72% of the energy in some processes, concluding "the importance of screen consumption (in a desktop client) validates efforts to improve the performance of web apps: the longer it takes for a user to achieve a task, the more energy they consume".
by Anders Andrae and Tomas Edler https://www.mdpi.com/2078-1547/6/1/117#abstract
As reported in Nature, and used by Website Carbon Calculator - to give 1.8kwh/gb.
Analysis for visuali.st: