A landmark decision by a top UN court has cleared the way for countries to sue each other over climate change, including over historic emissions of planet-warming gases.

But the judge at the International Court of Justice in the Hague, Netherlands on Wednesday said that untangling who caused which part of climate change could be difficult.

The ruling is non-binding but legal experts say it could have wide-ranging consequences.

It will be seen as a victory for countries that are very vulnerable to climate change, who came to court after feeling frustrated about lack of global progress in tackling the problem.

The unprecedented case at the International Court of Justice (ICJ) was dreamt up in 2019 by a group of young law students in low-lying Pacific islands on the frontlines of climate change.

“Tonight I’ll sleep easier. The ICJ has recognised what we have lived through – our suffering, our resilience and our right to our future,” said Flora Vano, from the Pacific Island Vanuatu, which is considered the country most vulnerable to extreme weather globally.

“This is a victory not just for us but for every frontline community fighting to be heard.”

The ICJ is considered the world’s highest court and it has global jurisdiction. Lawyers have told BBC News that the opinion could be used as early as next week.

Campaigners and climate lawyers hope the landmark decision will now pave the way for compensation from countries that have historically burned the most fossil fuels and are therefore the most responsible for global warming.

Many poorer countries had backed the case out of frustration, claiming that developed nations are failing to keep existing promises to tackle the growing problem.

But developed countries, including the UK, argued that existing climate agreements, including the landmark UN Paris deal of 2015, are sufficient and no further legal obligations should be imposed.

On Wednesday the court rejected that argument.

Judge Iwasawa Yuji also said that if countries do not develop the most ambitious possible plans to tackle climate change this would constitute a breach of their promises in the Paris Agreement.

He added that broader international law applies, which means that countries which are not signed up to the Paris Agreement are still required to protect the environment, including the climate system.

The court’s opinion is advisory, but previous ICJ decisions have been implemented by governments, including when the UK agreed to hand back the Chagos Islands to Mauritius last year.