A failure to slash global emissions is setting the world on a "catastrophic" path to 2.7 degrees Celsius heating, UN chief Antonio Guterres warned Friday just weeks before crunch climate talks. 

A report by the United Nations on 191 countries' emissions promises found that they would not meet the ambition of the Paris climate agreement to limit global warming to 1.5C above pre-industrial temperatures. 

Instead, it showed "the world is on a catastrophic pathway to 2.7-degrees of heating," Guterres said in a statement.