How I Measured 1 Tonne of CO2 from My AI Coding Sessions

I work as a carbon consultant for large companies. I also code every day with Claude Code. At some point, these two parts of my life started to feel contradictory, and I needed a number. So I built claude-carbon - a bash + SQLite tool that hooks into Claude Code's session lifecycle and estimates CO2 emissions per session, live in the status line. Here's what 4 months of data looks like. The numbers 367 sessions analyzed 215 kg CO2e measured over 4 months Projection: 0.9 to 1.5 tonnes/year (roughly a one-way Paris-New York flight) For context: the average French person emits around 9 tonnes/year total These numbers cover inference only - the energy consumed when the model processes my prompts and generates responses. Training, hardware manufacturing, cooling, and datacenter construction are not included. The real lifecycle footprint is higher. Inference alone adds about 10% to my individual carbon budget. Just from coding sessions. How it works The tool hooks into Claude Code's Stop eve