U.N. Secretary - General says time is running out for world leaders to lead . ` Leaders must act . Report is ` ` another canary in the gold mine , '' U.S. Secretary of State John Kerry says . U.N. calls for the reduction of greenhouse gas emissions by 2020 . IPCC says it is more certain than ever that humans are causing temperature increases .
U.N. Secretary - General says time is running out for world leaders to lead . Report is ` ` another canary in the gold mine , '' U.S. Secretary of State John Kerry says . U.N. calls for the reduction of greenhouse gas emissions by 2020 . IPCC says it is more certain than ever that humans are causing temperature increases .