US industry emits some 13 million metric tons each year, far more than the amount estimated by the US Environmental Protection Agency (EPA), said the findings published in the journal Science.

Researchers said the actual leak rate of 2.3 percent -- compared to EPA inventory estimates of 1.4 percent -- represents enough natural gas to fuel 10 million homes.

The dollar value of the lost gas amounts to $2 billion, said the report compiled by more than 140 researchers, in cooperation with 50 oil and gas companies that provided site access and technical advice.

"Scientists have uncovered a huge problem, but also an enormous opportunity," said co-author Steven Hamburg, chief scientist at the Environmental Defense Fund.

"Reducing methane emissions from the oil and gas sector is the fastest, most cost effective way we have to slow the rate of warming today, even as the larger transition to lower-carbon energy continues."

Methane is the main ingredient in natural gas, and packs more than 80 times the climate warming impact of carbon dioxide over a 20-year timespan, experts say.

Natural gas is a fossil fuel that emits less carbon dioxide than oil or coal, but its efficiency depends a lot on keeping methane leaks to a minimum.

Some oil giants have already begun to recognize the problem and take action.

BP sets its first methane target in April, and ExxonMobil committed in May to cut methane emissions. Shell and Qatar Petroleum have also committed to cutting methane emissions.

Researchers said the reason for the discrepancy between US government estimates and actual emissions "is likely a result of existing inventory methods not capturing methane emissions that occur during abnormal operating conditions, like malfunctions."