this is bbc news. i'm annita mcveigh, live in glasgow, where world leaders are gathering for the cop26 climate summit. as it begins, borisjohnson warns humanity has run down the clock on climate change and says urgent action is needed. this is very, very urgent. notjust for our country, for the whole world. and if i had to give a comparison, i would say it was a one minute to midnight moment. and the clock is ticking. un scientists warn that extreme weather events are the new normal — and the past seven years are on course to be the hottest on record. but the leader of china — the world's biggest polluter — will not attend the summit in glasgow — president xi