Back in the autumn, I found myself mulling on Net Zero and the 80:20 Rule. My conclusion was that a target of 90% or just 80% cut in carbon emissions (topped up with 10-20% offsets) may actually accelerate climate action.

Why?

Because costs above that threshold can rise dramatically, making 100% decarbonisation disproportionately more expensive than 80-90%. Here’s some hard evidence to back that assertion up, pinched/adapted from Michael Liebreich, which shows how decarbonising the US grid is relatively cheap until you get close to 90% then it shoots up. The last few tonnes of CO2 can cost 8-20 times as much as ‘easy’ tonnes to mitigate. So it makes sense to target the ‘easy’ majority before getting hung up on the really hard bits, otherwise everything could grind to a halt.

(BTW you can hear me talk to Michael on the pod here, he’s always worth a listen.)

If that sounds heretical, then don’t forget the SBTi’s rule of thumb that a 90% reduction is in line with the Paris Agreement. So even if your 10% offsetting falls flat, you’ve still done your bit to meet Paris obligations. If your offsets do work, which they should, you’ve gone above and beyond the call.

I created the slide above for our 12½ Kick Ass Sustainability Ideas for 2026 on 21 January – join us for this and 11½ other great insights to get your Sustainability/Net Zero programme up and running in 2026.