Untangling companies’ environmental claims these days can be a head-spinning endeavor, and reading Meta’s latest sustainability report is no exception. Depending on how you look at it, the company’s greenhouse gas emissions either grew or fell last year.

Confused? The discrepancy has to do with whether you’re assessing total or net emissions and, crucially, whether you’re considering the local impact Meta has in places where it operates.

It helps to take a look at the graph below from the sustainability report. The light gray bars show Meta’s total “location-based” greenhouse gas emissions. Those bars have risen steadily since 2019, climbing to a total of 14,067,104 metric tons of carbon dioxide equivalent in 2023. It’s a slight increase in planet-heating pollution over the past year.

The darker bars on the same graph, on the other hand, show “market-based” emissions falling over the past year. Looking at these numbers, Meta’s carbon footprint appears nearly half as small, reaching just 7,443,182 metric tons in 2023.

So, which number should we believe? Meta, unsurprisingly, highlights the smaller figure near the top of its report, a couple pages ahead of the graph. But it’s important to keep both figures in mind — especially given how difficult it is to suss out how effective market-based mechanisms can really be in eliminating the fossil fuel pollution causing climate change.

“They’ve almost halved their emissions on paper, but it’s really difficult to say how much they’ve reduced it in reality,” says Rachel Kitchin, senior corporate climate campaigner at the environmental organization Stand.earth.

When it comes to the larger, location-based emissions, she says, “You could argue that it’s what their emissions actually are.” Those taller gray bars on the graph reflect local pollution stemming from the electricity the company uses wherever it sets up shop. Data centers typically connect into the local power grid, so they run on the same mix of fossil fuels as everyone else. A majority of Meta’s data centers are located in the US, where 60 percent of electricity still comes from fossil fuels.

Companies like Meta can ostensibly cancel out or offset carbon emissions from their electricity use by purchasing those RECs. Unfortunately, the math doesn’t always add up in the real world. Companies often overestimate the amount of greenhouse gas emissions they think they’re reducing through RECs, a 2022 study of 115 companies found. The problem is that RECs have gotten so cheap that selling them isn’t necessarily enough to fund new clean energy projects.

There are ways to avoid those pitfalls, however. That’s why it’s still worth looking into Meta’s market-based emissions, which take RECs and other commitments to support renewable energy growth into account.

Buying locally makes a big difference. Companies like Meta can agree to purchase bundled RECs specifically tied to new renewable energy projects in the same region where they operate. That way, they can help get more clean energy onto the local power grid and into local homes, businesses, and its own data centers. Commitments to match electricity use with renewable energy on a 24/7 basis rather than on an annual accounting sheet can also have more impact. It incentivizes the construction of additional clean power sources that can balance each other out when the sun doesn’t shine or winds die down.

To its credit, Meta says supporting new wind and solar projects near its data centers is a priority. An economic impact study it conducted last year found that its support for 86 new wind and solar projects across 24 states in the US should add up to 9,800MW of renewable energy to local grids by 2025. For comparison, Texas had more than 15,000MW of utility-scale solar capacity as of last year.

“I would say, from reading their report, it seems as though Meta has broadly pursued a high-impact approach to renewable energy,” Kitchin says. This week, for example, Meta announced a new initiative to develop geothermal energy for new data centers.

Finding new sources of clean energy has become an even bigger challenge because of how energy-intensive it is to train new AI tools. “As we want to build more data centers, it’s going to be really important that the electricity grids around us continue to decarbonize,” Urvi Parekh, head of renewable energy at Meta, said in a call with The Verge this week. “Our data centers are online 24 hours a day so that users can access the products like Instagram and WhatsApp and others. And so what’s great about geothermal energy is that it can also supply electricity around the clock.”

There’s still a lot of progress to be made. Meta sourced 8.5 percent of its renewable energy purchases from less effective, unbundled RECs, according to an assessment of tech companies’ renewable energy spending that Stand.earth published earlier this year. In an email, Meta didn’t confirm whether that figure is still accurate — just that unbundled RECs make up a “small percentage” of its portfolio. Meta says it mostly enters into long-term agreements to purchase renewable energy from new projects.

But whether you look at the location or market-based emissions in its latest sustainability report, Meta’s carbon footprint is still significantly larger than it was in 2020. That’s the year it pledged to reach net-zero emissions by 2030 across its operations, supply chain, and consumer use of its products. Now, it’s even further from that goal than when it started.