Pope Francis could help reduce global carbon emissions by urging Catholics to return to not eating meat on Fridays, UK researchers said on 1 November.

A team at Cambridge University looked at the impact of a call by bishops in England and Wales in 2011 to reinstate the practice.

They found that despite only about a quarter of Catholics changing their dietary habits, more than 55,000 tonnes of carbon were saved each year.

In terms of carbon dioxide emissions, that equated to 82,000 fewer people taking a return flight from London to New York over a 12-month period.

The researchers said that if meatless Fridays were reintroduced across the world, it could mitigate millions of tonnes of greenhouse gases annually.

Lead author Shaun Larcom, from Cambridge's Department of Land Economy, said the Catholic Church was "very well placed" to help.

The Pope, who leads some one billion followers around the world, has said that climate change is an "unprecedented threat" needing urgent action.

"Meat agriculture is one of the major drivers of greenhouse gas emissions," said Larcom.

"If the Pope was to reinstate the obligation for meatless Fridays to all Catholics globally, it could be a major source of low-cost emissions reductions."

Even if only a fraction of Catholics went meat-free on Fridays, the reductions could be significant, he added.

The practice of not eating meat on Fridays is one of the oldest Christian traditions, with fish allowed as a protein substitute.

It has not been an obligation on Catholics since Vatican reforms in the 1960s, except during the Lenten period before Easter, which commemorates Jesus's death and resurrection.

The researchers pointed out the practice was observed so strictly by US Catholics that it led to the invention of the Filet-o-Fish meal by the burger chain McDonald's.

The study, published on the Social Science Research Network, was based on analysis of public health studies of dietary habits in England and Wales.