According to researcher Gautheir Roussilhe there are three main schools of thought for modelling digital ICT climate emissions:
Malmodin & Andrae are both Swedish; Malmodin is consider an optimist; Andrae & Lofti are considered pessimistic. Roussilhe sets this out on page 31 of this French language analysis that each view the ratio of impacts between Data Centre, Networks and Devices differently:
|Total footprint size||623 MtCO2e||1207 MtCO2e||690 MtCO2e|
The [[Shift Project]], Paris, March 2019 - 3.7% of total emissions in 2019, growing from 2.5% in 2013 (source). Widely quoted (the BBC, Climate Care & the New Scientist). Scope include production. Shift blames the growth on video.
Shift's estimates for video streaming have been challenged by the IEA: https://www.iea.org/commentaries/the-carbon-footprint-of-streaming-video-fact-checking-the-headlines - which Shift responded to, acknowledging the error but not adjusting their basic figure.