(Bloomberg) -- In April, Diversified Energy Co. told investors it had achieved a “marked improvement” in its environmental record: It had cut direct greenhouse gas emissions by 28% in a single year.

But the natural gas producer told a different story to U.S. regulators, who require companies with large facilities to report emissions each year. Those estimates, made public by the Environmental Protection Agency earlier this month, show Diversified’s emissions went up 19% over the same period of time.The diverging numbers highlight how difficult it is for investors to judge a company’s environmental performance. Amid a surge in shareholder interest, companies are now publishing detailed reports covering everything from automobile usage to recycling. Diversified’s April sustainability report, its latest, stretches to 66 pages, complete with photographs of smiling workers in hard hats. But there are no uniform accounting standards for these disclosures, and few consequences for misstatements. 

With 69,000 wells, most of them in the Appalachian region, Diversified is the largest well owner in the U.S. The company, headquartered in Birmingham, Alabama, and listed on the London Stock Exchange, was the subject of a story in Bloomberg Green last week focusing on its emissions of methane, a powerful greenhouse gas that is the main component of natural gas.

Rather than measuring emissions directly, oil and gas companies typically base their estimates on formulas, many developed by the EPA, that assign a uniform leak rate to each piece of oilfield equipment and activity. These estimates don’t take into account the carbon dioxide released when customers burn oil and gas—they just tally the amount of emissions that resulted from producing the fuel. For natural gas producers such as Diversified, the biggest contributor to emissions is methane that spills from wellheads, tanks, pipes and compressors, or is intentionally vented into the air.

Read More: Vast Empire of Dying Wells Is Spewing Methane—and Money

In the April sustainability report, Diversified explained that it “eliminated from service a number of devices with reportable emissions.” It was that work, the company said, that was “primarily responsible for the marked improvement” in its emissions from 2019 to 2020.

But Diversified acknowledged in response to questions from Bloomberg that the 2019 numbers in the sustainability report were wrong. In an emailed statement, the company said it had overstated how much equipment it had, leading to an inflated emissions estimate for the earlier year. Originally, Diversified reported similarly inflated 2019 figures to the EPA, but over the course of more than a year it amended them repeatedly, ultimately cutting the total greenhouse-gas emissions for that year by more than half, agency records show. That explains why the sustainability report showed emissions dropping, while the numbers reported to regulators went up.In the statement, Diversified acknowledged that some of the revisions to the EPA numbers took place prior to publishing the sustainability report with the outdated figure in early April. But it said a final amended report on 2019 emissions wasn’t sent to the agency until late April. Diversified didn’t mention the ongoing 2019 revisions in its sustainability report, nor did it update the report with more accurate numbers after the revisions were completed.

The market continues to rely on the inaccurate figures. On Monday, analysts at brokerage Peel Hunt reiterated their recommendation to buy Diversified shares, saying in part that environmental concerns are overblown. In a research note, Matt Cooper and Werner Riding pointed to what they called an “impressive” drop in annual emissions described in the sustainability report.

Asked about the report's claim of a “marked improvement” brought about by removing old equipment, Diversified pointed to the preceding sentence in the report stating that the company “significantly improved the accuracy” of its equipment counts. It doesn’t indicate whether any particular figures in the report are inaccurate.

“Diversified reports emissions accurately according to the rules and timing of regulators and the frameworks that structure our sustainability reporting,” the company said in the statement. “We are committed to further reducing emissions and by the very nature of what we do—investing in critical energy infrastructure—we have made substantial improvements that are reflected publicly in our disclosures.”The company’s most recent disclosures to the EPA show emissions rising 19% from 2019 to 2020, which Diversified attributed to acquisitions the company made. The count of most types of equipment rose between the two years as the company’s well count increased by 13%. Diversified said its efforts to remove equipment with high emissions rates helped limit the increase in emissions.

It’s unclear whether either set of estimates—those provided to investors, or the ones sent to the EPA—has much basis in reality. These formulas have come under scrutiny in recent years amid scientific research showing that they often systematically underestimate methane leaks.

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