CO2Stats

About CO2Stats

CO2Stats publishes measured, sourced numbers about carbon: atmospheric CO2 today and over 800,000 years, each country's emissions, the energy cost of digital life in the Kettle Question, and a guide to green web hosting. A website carbon checker is coming; its method is already published.

The original CO2Stats, 2007 to 2017

CO2Stats first appeared in late 2007 as a free widget, built by two graduate students, Alex Wissner-Gross and Tim Sullivan, that estimated the carbon cost of a website's visits and bought offsets to match. In 2008 their company, Enernetics, went through Y Combinator and made it a paid service: from a few dollars a month, a site displayed a "Green Certified Site" badge and a script that estimated the energy of each visit. In 2009 the company said it bought only renewable energy certificates to cover that energy, not carbon offsets; by 2016 its home page said "carbon offsets or renewable energy".

It was criticised, most loudly in January 2009, when a Sunday Times story attributed to Wissner-Gross the claim that two Google searches use as much energy as boiling a kettle; the Kettle Question tells that story. He said the figure was not his research, though he acknowledged passing the paper other people's figures. Critics, among them TechCrunch, two writers at the Guardian and the writer Nicholas Carr, pointed out that the researcher being quoted sold the remedy, and that the calculations behind his figures had not been published. In 2010 a green computing lecturer signed his own site up through Trustmarker, the company's badge site, and was given a "Green Friendly Site" certificate that, he wrote, required nothing more than self-certification.

Y Combinator records the company as acquired in December 2016. The last archived pages of the original service are from January 2017, and by December 2017 the address showed a parked page with advertising.

The relaunch

The domain lapsed, and in 2026 a new owner, who has no connection to the original team or company, relaunched it. The old badges and certificates are not coming back.

The criticism shaped the relaunch. The checker's method was published before the checker was built. Every figure links to its source, and the new badge, CO2Stats Verified, will state measured facts about one page with a date, never that a site is "green". We sell no offsets, and when a link could earn us money, the page says so before you reach it. The editorial policy sets out the rules.

Contact

Questions, corrections and anything else: hello@co2stats.com.

Sources for the history

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