Emissions for one email, from spam to a long message with an attachment. Each entry records the claim as published: what it counts, who made it and who paid,
and any dispute. Figures with different boundaries are not comparable without reading what each counts.
An email with a long attachment, How Bad Are Bananas? (2010)
50 g CO2e per email with attachment
50g CO2e: An email with long and tiresome attachment
One email, used for unnecessary "thank you" emails in the UK
Scope
not stated
Counts
not stated
Leaves out
not stated
Model or version
not stated
Place
UK
Period measured
not stated
Method
The press release takes 1 g per email from Mike Berners-Lee and multiplies it by survey-based counts of unnecessary emails (Censuswide, 3,000 British adults) to reach 16,433 tonnes a year.
Claimed by
Company: OVO Energy (citing Mike Berners-Lee)
Paid for by
none
Dispute
BBC News (November 2020) reported that Mike Berners-Lee, whose research was used, told the Financial Times the work was based on "back-of-the-envelope" maths from 2010, and quoted Chris Preist (University of Bristol) that most of the system uses energy whether or not an email is sent, so "the carbon saved will be far far less than 1g per email." https://www.bbc.co.uk/news/technology-55002423
History
Added.
A long laptop-to-laptop email (10 minutes to write, 3 to read)
17 g CO2 per email
If the editor took 10 minutes to write the email ... and it took me three minutes to read, and if it was sent from a laptop and received on one, then we have generated 17g of carbon dioxide (CO2) emissions already, according to estimates by Mike Berners-Lee, a professor at Lancaster University’s Environment Centre