Methane emissions caused by coal-mining activities in Indonesia, the world's largest thermal coal exporter, are severely under-reported due to outdated and inaccurate measurement methods, according to a report published Tuesday.

Ember, a London-based climate and energy think tank estimated that based on its studies, Indonesia's coal mine methane (CMM) pollution is up to eight times higher than official figures.

Methane is the second-largest contributor to global warming after CO2, according to the United Nations Environment Programme (UNEP).

The discrepancy in figures means "Indonesia could jeopardise its international standing as it is committed to slashing methane globally", Ember's senior Indonesia climate and energy analyst, Dody Setiawan, said in a statement.

Indonesia's energy and mineral resource ministry did not respond to a request for comment from AFP.

The archipelagic country is the third-largest coal producer in the world after China and India, and is the world's largest thermal coal exporter.

In 2023, Indonesia produced a record-high 775 million tonnes of coal, according to the energy ministry, with more than 500 million tonnes exported.

Indonesia is one of the signatories of the Global Methane Pledge (GMP) and the government has said that it is committed to "take comprehensive domestic actions to achieve the global reduction of methane emissions by 2030".

In its last biennial report submitted to the United Nations, Indonesia reported it had released 128 kilotonnes of methane emissions from surface coal-mining activities.

Ember, however, predicted Indonesia could potentially release more than 1,000 kilotonnes of methane emissions from coal-mining activities in 2024.

The group said Indonesia was using outdated methods to estimate its emissions, and was also failing to report CCM from underground coal-mining activities, which can be far higher than from surface mining.

Activists urged the government to improve its CCM management, identify which regions produced the most CCM, and address the under-reporting of methane pollution.

"Indonesia must plan to monitor its emissions, and improve the accessibility of its coal mining and methane data, to help fully achieve the goals of the Global Methane Pledge," said Dorothy Mei of Global Energy Monitor (GEM) in a statement.

Hendra Sinadia, executive director of the Indonesian Coal Mining Association (APBI), told AFP the data gap might be caused by a lack of standards in the measurement method, especially from fugitive emissions that are not reported by the companies.

"The measurement is not standardised... especially for the fugitive emissions which has a large contribution," he said.