Before you can cut your carbon footprint, you have to measure it. This is the second in a series sharing what we learn along the way to reaching net zero at Isometric. Read the first here.
Guesstimating
The next step after setting our net zero target, penciled in for 2030, was to calculate our most recent carbon footprint, the ‘Base Year.’
So, where to start? Getting the calculation right requires piecing together requirements from a number of SBTi publications, as well as the GHG Protocol Corporate Standard. But, before diving into that, I wanted to do a back-of-envelope calculation to provide a sanity check for the detailed work. With a lot of rounding, my guesstimate was that Isometric has a carbon footprint of around 200 tonnes per year.
- Flights: 120 tonnes. This instinctively felt like the largest part of our footprint. We’re a team of around 75 now. The Growth Team fly a lot; the Science Team a fair amount; Tech and Operations, approximately half the company, rarely. That’s about 40 people. At an average of 3 transatlantic flights a year—approximately 1 tonne for the round trip, since we always fly economy—that’s 120 tonnes.
- VVBs: 20 tonnes. I wasn't totally clear on whether to include Validation and Verification Bodies (VVBs) in scope. This is one where we need to read the really detailed guidance. For this exercise I assumed VVBs fit into our Scope 3 emissions, with the biggest consideration being site visits for project validation. In the past year, 20 Isometric projects were validated. At a conservative 1 tonne of carbon emissions per site visit, that’s 20 tonnes.
- Offices: 15 tonnes. First, electricity for our offices in New York and London. Googling based on the number of desks suggested 35,000 kWh, which is about 10 tonnes assuming a mixed grid. Second, travel: Isomers commute 3 times a week, mostly by train. Some walk, cycle, or bus, but nobody drives. That’s around 10,000 journeys a year. Transport for London estimates 0.5 kg of carbon emissions for a typical 10 km ride on the Underground, bringing the total to around 5 tonnes.
- Compute: 5 tonnes. Our product is software. The half of our team that isn't flying is still processing, transferring, and storing a lot of data. Over lunch, one of our software engineers shared some numbers: 70 CPUs of compute, 3 TB of storage, and 2 billion tokens on AI last month. That's much higher than six months ago. Total compute emissions come to around 1 tonne, while the storage is negligible. Estimates of AI’s carbon intensity vary a lot, but a mid-point seems to be around 0.3 tonnes per billion tokens. At roughly 15 billion AI tokens annually, that’s 4.5 tonnes. This brings the total to around 5.5 tonnes.
- Other: 40 tonnes. A catch-all for categories I haven’t covered, like catering, events, and things we buy for the office. I estimate this at about 40 tonnes, getting us to a round 200.
Getting real
That was the fun part. Now to do it properly. Our Chief of Staff, Clare, holds the overview on all our company’s spend and excels at Excel, so she took on the real work.
The more accurate figure came in at 332 tonnes, quite a bit higher than my estimate. This was mostly due to business travel, calculated using actual flight path data—‘activity based’ in the jargon. The other part I’d underestimated was Purchased Goods & Services. As well as covering VVBs and other consultant spend, there was a bigger line item on catering than I had expected, about 38 tonnes. In retrospect this made sense given that we have a weekly Team Lunch, host regular client dinners, and run an annual summit at London Climate Action Week (feeding more than 150 people adds up).
The harder part
SBTi asks companies to cut absolute emissions by 90% before offsetting the rest. For a growing company, that's a tall order. Isometric's headcount has grown significantly over the past year, and—barring a miracle in sustainable aviation fuel—we could cut emissions per person and still see our absolute footprint rise for years. High-quality carbon removal credits are clearly going to play a role in taking responsibility for the rest.
That said, the priority areas are clear: fewer flights where possible, and lower-carbon vendors for purchased goods and services, catering included. The question is how to organize this internally. Should we introduce an internal carbon price? Do we need a Chief Sustainability Officer? All still to be decided.
We now have both a target and a base year. What remains is preparing the rest of what SBTi requires for validation. Version 2.0 of the Corporate Net Zero Standard is expected in June 2026, and we'll submit shortly after it lands. That process will be the subject of the next post.
