Only urgent international action to cut emissions can prevent climate-related catastrophe, scientists warned on Friday.

Achim Steiner, director-general of the United Nations Environment Programme, said: “The word unequivocal [applied to the evidence that human activity was causing climate change] is the key message in this report. We’re looking for an unequivocal commitment [to emissions reduction] from policymakers, business leaders and civic society leaders.” For businesses or governments to continue to resist taking action on emissions was “irresponsible”.