The top United Nations court has taken up the largest case in its history, hearing the plight of small island nations facing rising sea levels.

The International Court of Justice, the United Nations’ highest judicial body, is beginning landmark hearings on global warming. Here’s a guide.

Environmental campaigners from 98 countries and 12 organisations began giving evidence on Monday to the International Court of Justice in a landmark case aimed at laying down rules for how rich nations should support poorer ones on the frontlines of climate change.