Around the world environmentalists are taking governments and companies to court to fight climate change. Joshua Rozenberg explores how the law is evolving into a powerful activists' tool.

In the first case of its kind, in a ruling that was upheld by the Dutch Supreme Court, the Netherlands were found to have a duty to reduce greenhouse gas emissions by 25% compared to 1990, and this by December of last year. What happened?

Apart from governments, companies are being sued by individuals or shareholders. For example, a Peruvian farmer has filed a case in a German court against a German electricity company for what he claims is its role in warming up the climate enough for him to be threatened by flooding as a nearby Andean glacier melts.

In Poland activist shareholders sued the board of their utility company to stop the development of a new coal mine, claiming an "indefensible" financial risk, due to rising carbon costs and falling renewables prices.

And senior lawyers are developing the concept of "ecocide", with the aim to make it an indictable offence at the International Criminal Court, analogous to genocide or crimes against humanity.

So how is the law evolving to tackle climate change, asks Joshua Rozenberg.

Producer: Arlene Gregorius