A leading British climate scientist has told the BBC he believes the target of limiting global warming to 1.5°C will not be met. Professor Sir Bob Watson, the former head of the UN climate agency, told the BBC's Today programme that he was "pessimistic". His warning comes in the middle of a summer of extreme heat for Europe, China and the US. The UN says exceeding the limit will expose millions more people to potentially devastating climate events. ((Esme Stallard & Justin Rowlatt, BBC News)