Christiana Figueres, executive secretary of the UN Framework Convention on Climate Change, warned that fossil-fuel assets may become “stranded” as climate regulations prevent them from being profitably developed.

“The time for experimentation, for marginal changes and for conditional response is now over,” she told the International Petroleum Industry Environmental Conservation Association in London.

Figueres has become more outspoken in her attacks on the fossil-fuels industry in recent months, as part of efforts to promote renewable sources.

She