Top global academics, lawyers and doctors are calling on the Dutch government to drop an appeal against a landmark court ruling which orders it to slash greenhouse gases by a quarter by 2020.

In a letter to Liberal Prime Minister Mark Rutte, they urge him and his cabinet to "reconsider your plan to appeal the Urgenda judgement," according to a copy obtained by AFP Tuesday.

The June judgement by a local judge has been hailed as a "milestone" by climate experts after 900 Dutch citizens, led by environmental rights group Urgenda, went to court in a bid to force a national reduction of emissions blamed for global warming.

But the government has said it will appeal the judgement, fearing the court's decision could have wider implications for how its policies are implemented. It has until Thursday to lodge an appeal.

"Climate change poses grave and imminent threats which have already begun to harm human communities, persons and the environment," said the letter sporting 20 signatures including by environmental and medical professors from Harvard, Yale, Columbia and London's University College.

The order to the Dutch government to cut greenhouse emissions by 25 percent by 2010 "is therefore of huge importance," added the letter, also inked by global aid group Oxfam.

Urgenda, which brought the case in April, said it wanted The Hague to reduce greenhouse gas emissions by 40 percent over 1990 levels by 2020.

Current Dutch policy is to reduce emissions by 17 percent by 2020, against the 25-40 percent international norm for industrialised nations, the court said.

The court found in favour of the rights group exhorting the government to do more.

"To solve the climate crisis, governments must accept that both the science and the law require them to act," said the letter.

"The Netherlands now has the opportunity to lead the way in spreading this simple but powerful idea!" it added.

The Dutch decision comes as some 195 nations are due to gather in Paris in three months to thrash out a new accord to drastically cut greenhouse gases.

But nations differ on how to divvy out responsibility for carbon cuts between rich nations -- which have polluted for much longer -- and developing countries, which need to power fast-growing populations and economies.