The pact targets the use of fossil fuels, increases funding for developing countries and concludes the Paris agreement rulebook.
Critics say it is not ambitious enough cutting emissions to ensure that global warming can be kept below 1.5 degrees.
Mr Johnson hailed the summit as a historic success that had dealt the death knell to coal despite a last-minute change demanded by China and India so that the pact promises to “phase down” coal power rather than phasing it out.
“Those for whom climate change is already a matter of life and death, who can only stand by as their islands are submerged, their farm land turned to desert, their homes battered by storms, they demanded a high level of ambition from this summit. While many of us were willing to go there, that wasn’t true of everybody. Sadly that’s the nature of diplomacy. We can lobby, we can cajole, we can encourage, but we cannot force sovereign nations to do what they do not wish to do,” he said.
Cop26 president Alok Sharma, who was close to tears as he apologised for the way the last-minute change to the text was made, said the fate of the entire pact had been in the balance.
“I can tell you there was that one hour where I really felt there was a chance there we were not going to get this deal over the line,” he said.
Minister for the Environment Eamon Ryan said China and India would face a lot of pressure over what phasing down coal actually amounted to but he said it was better to accept “that really gutting last-minute compromise” rather than lose the whole agreement.
‘Not doing that would have risked losing the whole thing and that would not have served anyone. We can’t delay, we’re in a crisis. There’s so much good in this, it gives structure and depth to the Paris climate agreement. We’ll have to continue to put pressure on and ensure that we do phase out coal,” he said.
The Cop26 Coalition, a group of some of the world’s biggest environmental organisations and civil society groups, said the outcome in Glasgow was a betrayal. Its spokesman Asad Rehman said: “It is hollow words on the climate emergency from the richest countries, with an utter disregard of science and justice. The UK government greenwash and PR have spun us off course.”
US special climate envoy John Kerry, who played an energetic role during the summit, strongly defended what had been achieved.
“We are in fact closer than we have ever been before to avoiding climate chaos and securing cleaner air, safer water and a healthier planet,” he said.