DSIT gets sums badly wrong on AI datacentre carbon footprint

Government figures for projected carbon footprint for datacentres have been miscalculated. New figures for the likely carbon output resulting from electricity use by datacentres published last week have been revised upwards by around 100x for the minimum and maximum projected. 

Last July, the Department for Science, Innovation & Technology (DSIT) published its Compute evidence annex, which set out the future for AI, compute demand and implications for carbon footprint. The DSIT has since unpublished the original report, but it can still be found here. 

The document said: “We estimate that by 2035, the UK’s greenhouse gas emissions from AI compute could range from 0.025 to 0.142 MtCO₂ [millions of tonnes of CO₂] – this is below 0.05% of the UK’s projected total emissions.”

But in a correction to that document, the DSIT said last week: “The UK’s cumulative 10-year greenhouse gas emissions from AI compute could range from 34 to 123 MtCO₂ – this is around 0.9-3.4% of the UK’s projected total emissions over the 10-year period.”

The figures were miscalculated to a staggering degree. The earlier numbers appear to have been annual and the recent revision a 10-year figure, which makes an increase in the estimate of around 100x.

Meanwhile, analysis by climate change science and policy research group Carbon Brief suggests even those figures might be optimistic. Core to that belief is that the government aim is for 50gCO2/kWh by 2030. That figure is what can be achieved by “clean” sources of energy, such as wind, nuclear, hydro and solar. 

But figures from last month – researched by Carbon Brief and published with environmental campaigners Foxglove – suggest that is a wildly optimistic estimate if any of that power generation needs to be powered by gas, as gas-powered electricity generation comes with a carbon intensity of around 10x that of clean sources. 

Carbon Brief has calculated that emissions could in fact be somewhere between 3.4 MtCO₂ using 5% gas, and 68.1 MtCO₂ if electricity was 95% gas-generated. The higher figure – not far off the annual carbon emissions of Sweden – comes from an estimate based on a recent Ofgem projection of 20GW of future datacentre electricity demand. The same document illustrated the scale of demand by reference to actual peak demand in February 2026 of 45GW.

Ofgem’s 20GW is a projection based on National Energy System Operator research that asked customers about future grid connection requirements. 

Foxglove head of strategy Tim Squirrell said: “The government has a legally binding commitment to reach net zero by 2050. This already sat awkwardly alongside its hell-for-leather embrace of a hyperscale AI datacentre buildout, which unchecked could double the electricity consumption of the entire country.

“The situation has now been revealed to be much, much worse, given the fact the government doesn’t seem to have done even the most basic arithmetic needed to measure the potential new carbon emissions of these datacentres. The government urgently needs to confront the reality that it can’t rubber stamp hundreds of new datacentres, whilst keeping its manifesto promise to the country – and legal obligation – to combat the climate crisis.”

Computer Weekly has calculated that there is currently around 1.6GW of datacentre capacity in the UK, with just over 8GW currently in planning or under construction.