The UK government vastly underestimated the climate impact of artificial intelligence, it has emerged, after officials raised their estimate of carbon emissions from AI by a factor of more than 100.

According to new data quietly published this week, energy use by AI datacentres in the UK could cause the emission of up to 123m tonnes of carbon dioxide (CO₂) – about as much as generated by 2.7 million people – over the next 10 years.

That latest figure replaces a previous estimate – since deleted – that claimed emissions would reach a maximum of 0.142m tonnes of CO₂ in a single year.

There is increasing alarm at the carbon impact of AI and with calls to reduce global emissions to mitigate the climate emergency becoming increasingly urgent.

Patrick Galey, the head of investigations for the Global Witness climate campaign, said: “We have a handful of years until our carbon budget is exhausted.

“To waste what little bandwidth we have left – when 750 million people worldwide lack access to electricity – assisting some of the richest men ever to hone their plagiarism bots would be a historic idiocy that future generations are unlikely to forgive today’s leaders for.”

The latest estimates were revealed in a revision to the UK “compute roadmap”, which sets out the government’s plan “to build a world-class compute ecosystem” for delivering artificial intelligence in the UK – a goal on which the government has staked its hopes for economic growth.

However, AI datacentres require huge amounts of electricity to operate – much more than the datacentres used to store online data – and most of that continues to be generated by fossil fuels.

According to the Department for Science, Innovation and Technology’s (DSIT) latest estimates, the carbon impact of the planned AI buildout could range from 34m to 123m tonnes of CO₂ – about 0.9% to 3.4% of the UK’s projected total emissions between 2025 and 2035. The lower range of the estimate would depend on greater efficiency in AI models and hardware, and faster decarbonisation of the UK’s energy grid.

Officials from the DSIT appear to have made the revision, first reported by Politico, after an investigation by Foxglove, an independent watchdog, and the Carbon Brief news site said they appeared to be a significant underestimate.

Foxglove’s 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 declined to comment on the record.