The UN's top court on Wednesday ruled climate change an "existential problem of planetary proportions" and said countries had a legal duty to act or face consequences.

One of the world’s most vulnerable countries to the fallout from climate change has won a landmark legal battle, giving countries new ammunition to pursue some of the planet’s biggest emitters.

In a landmark decision, the International Court of Justice found that polluting countries are now legally obligated to address global warming. In a unanimous ruling by a panel of 15 judges, the court said high-emitting countries do have legal obligations under international law to address the “urgent and existential threat” of climate change.