Companies can, in theory, appear to cut the carbon footprint of their supply chains in half simply by changing how they calculate emissions, according to a new paper. Researchers found that differences in accepted accounting methods can change how companies crunch their climate numbers and make it difficult to distinguish real emissions cuts from differences in calculations.

“It is actually possible … in the current framework that a company can either look like a climate pioneer or a climate laggard just depending on which numbers they pick,” lead author Ramana Gudipudi, a guest lecturer at the European School of Management and Technology in Germany, told Mongabay by phone. “If I am a company, all I need to do is to hire a good mathematician and say like, ‘Hey, this is how much I want to show my progress.’”

The analysis, published as a peer-reviewed perspective in the journal Nature Sustainability, looked at 401 European companies and found that 62.5% of their year-to-year variation in supply chain emissions could not be explained by changes to the business, industry, or emission intensity. By contrast, accounting for the companies’ direct emissions only varied by a bit more than 5%.