Global emissions of methane could be double current estimates - posing an extra hurdle to fighting climate change, say researchers.

The study, published in peer-reviewed science journal Nature, is based on a database 100 times larger then previous ones.

It says methane produced during the production of oil, coal and natural gas is 20 to 60% higher than thought.

"Both emissions inventories and atmospheric studies have underestimated methane emissions from fossil fuel development," said Stefan Schwietzke, the lead author of the study.

Taking into account methane also produced by natural sources, emissions are said to be "60 to 100% greater than current estimates".


Efforts to cap global warming to under 2C, as set out in the landmark Paris Agreement, could be more difficult if the study is accurate.

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There may not be as much methane in the atmosphere as carbon dioxide, but it is 28 times more efficient at trapping heat over a 100-year period. It is the second largest contributor to global warming.

Methane emissions peaked in 1999, remained constant until 2007 and then began rising sharply.

Natural sources of methane - for example wild animals, termites, wildfires and wetlands - account for a significant proportion of emissions.

But most is produced by human activity, such as fossil fuel production, cattle farming and landfills.

The Paris Agreement will come into force next month after it passed a threshold for ratification on Wednesday, widening to nations representing 56.75% of greenhouse gas emissions - above the 55% needed for implementation.

President Obama heralded the deal - which vitally includes the US and China - as "historic ... in the fight to protect our planet for future generations" and a potential turning point in fighting climate change.

It requires governments to come up with action plans to reduce emissions to below 2C and to report back with progress. The targets are not legally binding.