Microsoft, Amazon and Google’s collective carbon emissions have increased by nearly a fifth in the past year, driven largely by datacentre construction.

In the financial year ending March 2026, the three tech companies emitted 119m mTCO₂e (metric tonnes of carbon dioxide equivalent), or about a third of those of France.

The previous year, they emitted roughly 101m mTCO₂e, roughly equivalent to the 2024 emissions of Czechia.

The US companies’ climate ambitions have been hit in recent years by a boom in demand for cloud services, such as storing data or running servers over the internet, related to training and operating chatbots and other AI products.

Cecilia Rikap, an economics professor at University College London, said: “Claims by Microsoft, Amazon and Google about their clouds being ecologically friendly and sustainable are a marketing strategy. Governments should remember these expanding carbon footprints when the very same companies offer addressing the ecological crisis with AI solutions.

“And, as migration to their clouds expands, and companies store data and train and use AI models and all sorts of digital technologies, these other companies are outsourcing their own digital/AI carbon footprint to cloud giants. Basically, shifting to the cloud helps other corporations obscure their environmental footprint.”

Microsoft, Google and Amazon were contacted for comment.

These increases were documented in the companies’ annual sustainability reports, which they have released over the past weeks. In its report released on Thursday, Microsoft said its carbon emissions had increased by 25% over the past year to 20m mTCO₂e, “driven primarily by the expansion of our datacentre infrastructure”.

Google said its emissions had increased 18% over the past year, “driven by increases in supply chain activities that supported the rapid expansion of our business”. The search company says its AI systems have come up with solutions that have already helped to reduce emissions elsewhere by 41m tonnes of CO₂ last year.

Amazon reported a 16% increase in emissions overall, and a 20% increase in supply chain emissions, which included datacentre building and construction. In its report, it still framed this as “making progress” towards its goal of net zero emissions in 2040.

The bulk of these emissions come from a big, global push to build the infrastructure for artificial intelligence. The world’s biggest tech companies are on track to spend $765bn (£570bn) this year, mostly on building AI datacentres – in locations from Norway to North Tyneside.

It is a drastic reversal in a years-long push by big technology companies to cut their carbon emissions. Prior to this year, Microsoft’s emissions appeared to have flatlined, at 16m mTCO₂e, in 2023 and 2024. All three companies still say they aim to achieve net zero emissions: Google and Microsoft by 2030, Amazon by 2040.

“The increases in total carbon emissions are strongly correlated with [the companies’] AI investment,” said Shaolei Ren, a professor of electrical engineering at University of California, Riverside.

He noted that Microsoft’s sustainability report also suggested that there were fewer carbon credits available on global markets to offset its emissions. “While companies are actively investing in or purchasing carbon credits, the figure suggests a possible lack of credit supply in the carbon market to meet the technology companies’ needs … Everyone is talking about the lack of physical goods and infrastructure like power, but there may also be a lack of virtual goods – carbon credits.”

Proposals for building datacentres across the global tech sector are becoming more numerous and ambitious as demand for AI tools, and investment by AI companies in the models that underpin them, increases. JLL, a US property consultancy, expects about 1,200 datacentres to be built globally between now and 2030, with demand overwhelmingly driven by AI.

The datacentre boom is accompanied by vast projected power demands. The Uptime Institute, which rates and inspects datacentres, estimates that big datacentre projects announced last year would consume 1.3% of the world’s electricity usage, or a near-doubling of current datacentre demand. The majority of that new power demand will come from US projects, it said.