Speaking at the COP26 climate summit in Glasgow, he said the doomsday clock "is still ticking", but "we've got a bomb disposal team on site".

World leaders are leaving the summit, with negotiators for each nation taking over to agree on climate pledges.

More than 100 countries agreed on Tuesday to cut emissions of methane.

The US-EU global partnership aims to limit the emissions by 30%, compared with 2020 levels.

As the second full day of the pivotal summit concluded:

*  Mr Johnson warned "we must take care against false hope" as negotiators thrash out further deals

*  He urged richer countries to meet their promise to send $100bn (£74bn) a year to less developed countries faster

*  US President Joe Biden hailed progress made at the summit so far - but criticised China and Russia's leaders for not showing up

*  More than 100 nations - including Brazil - pledged to end and reverse deforestation by 2030

Despite some notable absences, senior figures championed the breakthroughs made as world leaders began to depart Glasgow, leaving behind teams of country negotiators for the next 10 days.

Mr Johnson said a pledge by Indian prime minister Narendra Modi to switch half the country's power grid to renewable sources by 2030 was a "massive commitment".

"I've seen more energy and more commitment and more urgency than I've ever seen and I've been doing this since 1988," US climate envoy John Kerry said.

But there is some way to go if leaders are to get an agreement that would keep alive the prospect set out in the Paris Agreement of restricting global temperature rises to 1.5C, according to the prime minister.

China is said to be one of those pushing back against a focus on limiting warming to 1.5C.

Mr Johnson told a news conference "one thing that gives me optimism - for the countries who find it most difficult to transition from fossil fuels, we're starting to form those coalitions to help them".

But he added that "if we don't fix our climate, it will be an economic catastrophe as well as a environmental catastrophe".

COP26 climate summit - The basics

*  Climate change is one of the world's most pressing problems. Governments must promise more ambitious cuts in warming gases if we are to prevent greater global temperature rises.

*  The summit in Glasgow is where change could happen. You need to watch for the promises made by the world's biggest polluters, like the US and China, and whether poorer countries are getting the support they need.

*  All our lives will change. Decisions made here could impact our jobs, how we heat our homes, what we eat and how we travel.

He said the public "may not listen to me, but they certainly listen to Sir David Attenborough (who spoke at the summit on Monday) and they look at what's actually happening around the world", referring to natural disasters in recent years.

Ahead of the summit, hosted by the UK, he had compared the fight against further climate change to a football match - suggesting humanity was 5-1 down at half-time.

With the world already experiencing dangerous heating, it's vital for this conference to produce more than what the activist Greta Thunberg calls "blah blah blah".

Today world leaders have announced initiatives of some significance.

In one declaration, more than 100 countries promised to reverse deforestation by 2030. The pledge includes almost £14bn ($19.2bn) of public and private funds.

Another major announcement is a pact to cut emissions of methane by 30% by 2030.

The third eye-catching action was an agreement between 40 nations, including the UK, China, India and the US, to work together to create standards and incentives for new technologies.

And in a fourth announcement, the governments of France, Germany, the UK, the US, and the EU, have outlined a partnership to get South Africa off coal, with an initial funding of £6bn ($8.5bn).

These actions together won't solve the climate problem. But they do demonstrate some valuable new thinking.

The prime minister said: "We've pulled back a goal, or perhaps even two, and I think we are going to be able to take this thing to extra-time, because there's no doubt that some progress has been made."

Shadow business secretary Ed Miliband responded by saying: "The score that really matters is whether we cut carbon emissions by half this decade."

Mr Johnson also said that while the "doomsday clock was still ticking" - having previously said it is at a minute to midnight - there was now a bomb disposal team on site and "they're starting to snip the wires - I hope some of the right wires".

As he prepared to return to London, Mr Johnson told the teams remaining in Glasgow: "The eyes of the world are on you - the eyes of the British government and all the other governments that care about this - and we have got your numbers."

The COP26 global climate summit in Glasgow is seen as crucial if climate change is to be brought under control. Almost 200 countries are being asked for their plans to cut emissions, and it could lead to major changes to our everyday lives.