The world has only six months in which to change the course of the climate crisis and prevent a post-lockdown rebound in greenhouse gas emissions that would overwhelm efforts to stave off climate catastrophe, one of the world’s foremost energy experts has warned.

“This year is the last time we have, if we are not to see a carbon rebound,” said Fatih Birol, executive director of the International Energy Agency.

Governments are planning to spend $9tn (£7.2tn) globally in the next few months on rescuing their economies from the coronavirus crisis, the IEA has calculated. The stimulus packages created this year will determine the shape of the global economy for the next three years, according…