Microsoft’s latest sustainability report sparked claims that the company produced 34 million metric tons of carbon emissions in a single year. That figure was never reported by the company. What the report actually shows is a 25 percent year‑over‑year increase driven by AI datacenter expansion and Microsoft’s decision to stop buying unbundled renewable energy certificates.
The Microsoft Environmental Sustainability Report shows a complicated progression of rising emissions caused by AI datacenters, controversial “greenwashing” tactics, and enough wiggle room to leave space for debate.
Real emissions vs estimated emissions
When I first read the coverage surrounding the Microsoft Environmental Sustainability Report, it seemed like a clear case of AI hurting the planet and a tech giant callously damaging the environment. I was ready to write a piece calling out Microsoft for setting carbon neutral goals and then increasing carbon emissions by 25% in a single year.
But as I do with any story I cover, I went to the source material and did some digging. What surprised me is that the Microsoft Environmental Sustainability Report does not indicate unbridled burning of fuel to power AI datacenters. Instead, it shows efforts to reduce emissions and make meaningful changes.
I want to be clear, AI datacenters do create high carbon emissions. Microsoft is not faultless when it comes to energy use or pollution. I think there is a lot more the company could do to help the environment. I also think there’s some misunderstood data seeping onto social media and throughout the web.
The above chart from the Microsoft Environmental Sustainability Report shows Microsoft’s actual reported emissions over the years and the estimated emissions without select interventions. The footnote on the chart directs to a clarifying statement on the estimate. I’ll include the full footnote here but highlight the most relevant text:
“The solid line represents Microsoft’s reported greenhouse gas emissions (Scopes 1, 2, and 3) for FY20–FY25, prepared in accordance with GHG Protocol and management’s criteria, and uses a market-based emissions approach. The dotted line represents an illustrative counterfactual scenario of estimated emissions had select, discrete carbon reduction initiatives not been undertaken. These initiatives include energy efficiency improvements for XBOX consoles, renewable energy purchases, sustainable aviation fuel (SAF) and sustainable marine fuel (SMF) certificates, and supply chain decarbonization of Surface devices. The difference between the two lines is an estimate of emissions avoided through these specific initiatives relative to a scenario without those initiatives occurring. This estimate is directional in nature, does not represent the full scope of Microsoft’s decarbonization efforts, and is not part of our reported greenhouse gas inventory. It should not be interpreted as a comprehensive measure of total emissions reductions or as additive to other carbon reduction or removal claims.”
Basically, the chart shows Microsoft’s actual emissions and then a rough estimate of how much the company would have emitted had it not taken steps to reduce its carbon footprint. But Microsoft did take those steps. Microsoft did not have 34 million metric tons of carbon emissions in the last year. The actual emissions figure is 20 million metric tons.
That’s still a massive amount of emissions, and 20 million metric tons is a 25% increase year-over-year, but there’s some needed context.
What are unbundled renewable energy certificates?
Microsoft’s carbon emissions increased by 25% in a single year. The increase was driven primarily by Microsoft’s expansion of datacenter infrastructure and the fact that the company paused the purchase of unbundled renewable energy certificates.
In February 2025, Microsoft announced that it “ceased purchasing non-additional, unbundled renewable energy certificates.” That decision led to the massive jump in emissions seen in the recently published sustainability report (in conjunction with AI datacenter infrastructure expansion).
Renewable energy certificates (RECs) represent the legal ownership of the “renewable-ness” of generated electricity. Unbundled RECs are sold separately from the electricity itself.
The United States Environmental Protection Agency notes that “Unbundled Renewable Energy Certificates (RECs) refer to RECs that are sold, delivered, or purchased separately from electricity. RECs provide no physical delivery of electricity to customers and as such the customer is purchasing power from a separate entity than the one selling them the REC.”
The separation of generated electricity from the legal ownership of the “renewable-ness” is controversial (that phrase comes straight from the EPA).
Many, including myself, view unbundled RECs as a form of greenwashing. Microsoft or any other company can legally say they are powered by renewable electricity without actually using the electricity that was generated.
The defense is that buying unbundled RECs financially contributes to the development of renewable energies.
Microsoft did not refer to unbundled RECs as a form of greenwashing, but its statement is telling:
“While we continue to apply the carbon fee to investments in emissions reductions, we have ceased purchasing non-additional, unbundled renewable energy certificates. We are refocusing the use of these funds on more long-term, higher-impact investments across carbon reduction, carbon removal, and clean electricity procurement. These interventions are expected to more effectively help us achieve our goal of becoming carbon negative by 2030 and may take us out of carbon-neutral position.”
Microsoft implied that unbundled RECs are not the most effective way to have a long-term positive impact on the environment.
The rest of the report
The Microsoft Environmental Sustainability Report is 65 pages of dense information. It links to several external resources as well. If it were a paper report, there’d be a good joke here about an environmental report killing so many trees.
A large portion of the report is dedicated to discussion about Microsoft’s use of water, which is a critical component of its environmental strategy. Notably, Microsoft replenished more water than it withdrew in the year.
Because of the size of the report, I’ve focused on the carbon emissions of Microsoft, but I suggest people read the entire report to get perspective on what’s being done and where Microsoft still falls short.
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