(Bloomberg) -- The quality of corporate emissions data available from third party services is too poor to make sound investment judgements, according to a new study by asset manager Research Affiliates.

Investors are trying to pick companies that will perform well in a carbon-constrained world, which requires knowing a company’s emissions, its future projections, and comparing that to its peers. But that information is often either unavailable or unreliable, says Vitali Kalesnik, the quant firm’s head of research.

Kalesnik and researchers from the University of Augsburg in Germany studied four corporate-emissions databases. Only about half the companies in these databases voluntarily disclosed their emissions, while some made estimates based on reasonable assumptions. The researchers wouldn’t name the databases to avoid labeling them as bad, though Kalesnik said the conclusion is true across all databases he could access.

“Our results debunk the belief that third-party estimated emissions are a satisfactory substitute for company-reported emissions,” said Kalesnik. That is why we “call for mandatory and audited carbon-emissions disclosure,” he said.

Kalesnik and his colleagues analyzed various third-party emissions databases thousands of times using different techniques. They compared, for instance, the estimates a database made in 2015 for companies that didn’t voluntarily disclose their emissions at that time against the same companies’ disclosures the year after. Another method was to compare the projections a database made in 2012 of a company’s 2016 emissions with the actual figures reported by the company that year. They concluded that the quality of predictability based on available information was poorer than investors would need to make good decisions.

“There’s really no excuse for not doing a good job,” said Jonas Rooze, head of sustainability research at BloombergNEF. Emissions reporting “guidance is nearly 20 years old now,” he said. “Still, reporting is very patchy and regulatory enforcement and auditing do seem inevitable.”

Kalesnik said that Research Affiliates has built a climate transition index inspired by the research. It penalizes companies that have their emissions estimated by third parties rather than voluntarily disclosing them.

“Companies that don't disclose emissions should be treated with great concern by investors,” said Rooze.

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