Updated September 4th 2013
Internet footprint today: 830 MT : Science Daily report
Internet footprint 2020: 14 GT : The Climate Group, SMART2020
The Web is 40% of internet traffic : Sandvine Global Trends
Data transmission takes 13 kWH per GB : Lawrence Berkeley National Laboratory report
It takes 1.2lb CO2e to make a kWH : EPA carbon calculator (USA average figures)
Viewing a web page may user 20-300 mg CO2 : Tech news world, Harvard Prof sets the Record straight on Internet Carbon
The average webpage is 1.4 MB: HTTP Archive Interesting facts
Web page is 15x bigger than 10 years ago: Web Optimization page size
Mobile data (3g, 4g) generates 77lb per GB: IEEE "Green communications by demand shaping and user-in-the-loop tariff-based control"
HTTP requests also cost energy: Mightybytes HTTP article
1 tweet = 0.02g CO2e. 500m tweets/day = 10 tons. 3,650 t/ year. : Treehugger Twitter
How Green is your website? Ecograder
Use Green hosting: supplier list
Join a Corporate Carbon scheme: Climate Declaration
The internet will save us 8 Billion Tons of CO2e by 2020 : SMART 2020
Web vs newspaper case study: Guardian "Digital Carbon Footprint". 1/3 of the Guardian's footprint is from digital.
Data Centers Are Becoming Big Polluters, Study Finds : NY Times
Sympact (Uni of Bristol) Exploring the environmental impact of digital transformation
Sustainable Virtual Design : Pete Markiewicz's site has a wealth of articles and facts and is regularly updated.