I just posted an article on the blog of the TCS4F initiative about how to understand the carbon footprint of various kinds of activities. You can read it here: Estimating carbon footprints: what is 1 ton of CO2e?.

Writing this kind of posts is a bit hard for me, because I'm certainly not an expert on climate change, so I don't feel very legitimate and hope that what I am saying there is realistic. Still, I hope that doing my own statistics is better than being completely in the dark. Anyway, reading about all this was the occasion to discover many surprising things about my own footprint, which can help me focus my efforts on the right areas. Personally here were the surprisingly high numbers, based on figures from the post:

• The plane trips I take (most of which are for work) probably have a carbon footprint which is greater that all my other sources of emissions combined: several tons of CO₂e per year, if not dozens of tons¹. So this was the main takeaway: the number one area on which I should work is on travelling less to distant places : avoiding a transcontinental plane trip saves tons of CO₂e emissions.
• The carbon footprint of heating my flat (collective heating) is already about 1.2 tons of CO₂e per year. Probably a bit less overall than the footprint of the food I eat, but certainly not negligible, even though I don't think much about it and have little control over it...
• In a sense, the few Bitcoin transactions I have done last year may have ended up corresponding to several hundred kilos of CO₂e on their own. I would never have guessed.
• Not using a car probably allows me to save around one ton of CO₂e per year in emissions from fuel for my commute, and several additional tons in terms of not having to produce the car.

And here were the surprisingly low numbers:

• Avoiding meat only saves around 600 kg CO₂e per year. This has a huge impact if everyone does it, but at my individual level it is rather small compared to the impact of one single long plane trip. Also, the most important food to avoid is unquestionably beef, and avoiding non-local food (e.g., bananas) does not seem to be worth it (see this study). So I'm still onboard with reducing my meat consumption, but transgressing every now and then isn't probably so much of a deal.
• The carbon footprint in France is really low, thanks to the predominant use of nuclear power (not to mention other environmental costs, of course), so my total consumption of around 1800 kWh per year only represents around 18 kg CO₂e.
• Likewise, I was surprised to see that the estimated CO₂e footprint of producing a mobile phone is only around 80 kg CO₂e, and producing a T-shirt is only around 7 kg CO₂e. Again, this says nothing of other environmental costs, but it is lower than I would have expected. I'm still not a fan of buying new hardware just for the sake of it, but apparently it's not such a huge deal in terms of greenhouse gas emissions.

I encourage you to read the post, which can hopefully give you a better idea of how your activities are producing CO₂e, and what's the best way to help by reducing your emissions. And of course I'd be delighted to hear back if you have questions or comments about the results.