A new United Nations report warns that progress toward prosperity in the world’s poorest regions will be reversed unless rich countries promptly begin curbing emissions linked to global warming while also helping poorer ones leapfrog to energy sources that pollute less than coal and oil.

The world’s poorest regions will also need much more help than has been provided to adapt to climate changes that are already unfolding, said the authors of the study, the United Nations’ annual Human Development Report.