COP27: We cannot go wobbly on climate change, says Boris Johnson
Watch: Boris Johnson says he is at COP 27 in 'purely supportive role'
Boris Johnson has said nations cannot "go weak and wobbly" on climate change targets, as he attended COP27 in Egypt.
Speaking in Sharm el-Sheikh, the ex-prime minister said the aim of reducing greenhouse gas emissions had suffered as a result of the Ukraine war. 
His comments were echoed by UK Prime Minister Rishi Sunak and French President Emmanuel Macron on Monday.
Mr Johnson also said he was glad Mr Sunak was attending COP27 - adding he was on "absolutely the right lines".
In return, Mr Sunak said the presence of both the current and former prime ministers showed the UK's commitment to tackling climate change.
"It is great that the former prime minister is here," Mr Sunak said. "It just demonstrates our leadership on this issue globally."
World leaders have gathered at the Red Sea resort for two weeks of talks on climate action.
On Monday evening, Mr Sunak addressed the summit, insisting that investing in green infrastructure is morally the right thing to do. 
He also told those gathered that the war in Ukraine is a reason to act faster to tackle climate change.
"Climate and energy security go hand-in-hand," he said in his first international appearance since taking office.
"Putin's abhorrent war in Ukraine and rising energy prices across the world are not a reason to go slow on climate change. They are a reason to act faster," Mr Sunak said.
Earlier in the day, speaking at a New York Times event, Mr Johnson warned it was not the moment "to give in to Putin's energy blackmail".
"The reason I'm here is because I am worried that the discussion about Ukraine, about what's happening there, is having all sorts of bad effects," he said. 
"It's making people anxious about net zero, it's making people anxious about whether we can really do it."
He continued: "I think that the risk is that some people will go weak and wobbly on net zero, we can't have that."
In simple terms, reaching net zero means getting to a point where you are not adding to the amount of greenhouse gases in the atmosphere.
It can be achieved by reducing greenhouse gas emissions as much as possible and balancing out any that remain by removing an equivalent amount - either through natural means, like trees, which absorb carbon dioxide, or using technology. Many countries, like the UK, have set targets of reaching net zero by 2050.
Mr Johnson warned "corrosive cynicism" had developed over net zero following the spike in oil and gas prices. 
"People have drawn the conclusion that the whole project of net zero needs to be delayed, mothballed and put on ice - for instance we need to reopen coal-fired power stations and frack the hell out of the British countryside," he said, in an apparent dig at his successor Liz Truss. 
"So I believe here at Sharm is a moment where we really have to tackle this nonsense head on."
Some Conservative MPs have called for a rethink of how the UK gets to net zero, with candidates in the summer's Tory leadership contest voicing concerns about the economic cost.
Ms Truss's government ended the ban on shale gas fracking before her resignation as prime minister. Her successor Mr Sunak has since reinstated the ban, a 2019 Conservative manifesto pledge.
Mr Johnson explained he was at COP27 in a "purely supportive role". 
Mr Sunak initially said he would not attend COP27. He changed his decision following criticism from climate campaigners, opposition parties and COP26 President Alok Sharma.
When asked if Mr Sunak was wrong to push for more oil and gas from the North Sea, Mr Johnson said it was right in the short term to recognise that there would be a transition period.
Mr Johnson added: "[Rishi Sunak] made an outstanding speech the other day. He's on absolutely the right lines."
was a very Johnsonian example of self-promotion.
"I am the spirit of Glasgow's COP26," he told the New York Times audience.
man who once criticised wind power as not capable of "pulling the skin off a rice pudding", is now ridiculing a Daily Telegraph journalist who questioned wind power's capabilities.
He boasted about the great achievements he claimed for the COP conference he oversaw as British prime minister.
re certainly were some ambitious pledges on finance, forests, cars, coal, methane and more made there.
But this conference is about delivering on those promises and that is a much tougher agenda. Tougher, because it means getting countries to actually cough up cash.
Johnson urged his audience to call forth the "can-do Promethean spirit that will get us out of this mess".
Put the electric throttle to the floor was his message.
But was this really directed at the audience in the hall or at the UK's current prime minister, Rishi Sunak, attending the leaders' reception here in Egypt, a few miles away?