Is there any data about the CO2 emissions per individual Google search?
Or are there none because Google is moving towards 100% renewable energy supply?
- Just the search query, no lifetime emissions
- Excluding my PC, home or city consumption
As LShaver and Gerrit also mentioned in their comments, an exact answer would depend on the scope and method of calculation. You've already mentioned you are only interested in the search itself so I guess this means you don't want to include (part of) the footprint of Google's servers, the web-indexing process, or information storage about your query. But what about the energy for transferring the data via various internet servers? And do you agree that Google's carbon offsetting program or the renewable energy they generate, both count as a negative component in the calculation?
One of the numbers that has been circulating on the Internet for years, is that a single Google search has a carbon footprint of 7 grams of CO2. This number allegedly was based on calculations done by Alex Wissner-Gross and was published in the Sunday Times in 2009, but after publication Wissner-Gross claimed he never mentioned such a number. In any case Google's response to the article was that the calculation is incorrect and that 0.2 grams of CO2 per search is more accurate. This number includes energy for some pre-query processes, such as building Google's search index.
It wasn't until 2011 that Google made its company energy usage public for the first time. At the time they repeated the 0.2 g CO2 per search. At the moment of writing this, the latest data from Google is from their 2017 environmental report. Google says that the entire company is responsible for about 2.9 million metric tonnes of CO2e (data 2016), all of which is off-setted by 'purchasing high-quality carbon offsets'. Google claims that by buying carbon offsets they have been carbon-neutral since 2007 and that in 2017 they will generate enough renewable energy to compensate the energy consumption of all Google operations.
I haven't been able to find recent data on a single Google search, but Google does say in their 2014 online environmental report that:
If you take an active Google user—someone who does 25 searches and watches 60 minutes of YouTube a day, has a Gmail account and uses our other services—Google emits about 8 grams of CO2 per day to serve that user. In other words, serving a Google user for a month is like driving a car one mile (source)
Note that this number was derived by Google itself. It doesn't seem possible to check it and find out what exactly is or is not included in that footprint. Interestingly the same 8 grams was already reported in 2013 based on 2012 data. With all the measures Google has taken in recent years, I expect it is a lower number now.