The UK minister tasked with leading UN climate talks says world leaders are failing to show the necessary level of ambition.
Alok Sharma was speaking at the conclusion of a virtual climate summit organised by the UK, UN and France.
He said "real progress" had been made and 45 countries had put forward new climate plans for 2030.
But these were not enough to prevent dangerous warming this century, Mr Sharma explained.
Taking place on the fifth anniversary of the Paris climate agreement, the summit heard the UN Secretary General warn that every country needed to declare a climate emergency.
Around 70 heads of state and government took part in the meeting, which was organised by the UK, UN and France. They outlined new pledges and commitments to curb carbon.
China's contribution was eagerly awaited, not just because it is the world's biggest emitter, but because it has recently promised to reach net zero emissions by 2060.
Achieving net zero means that emissions have been cut as much as possible and any remaining releases are balanced by removing an equivalent amount from the atmosphere,
But while President Xi Jinping outlined a range of new targets for 2030, many analysts felt these did not go far enough.
India brought little in the way of new commitments but Prime Minister Narendra Modi said his country was on track to achieve its goals under the Paris agreement and promised a major uptick in wind and solar energy.
According to the UK, some 24 countries had outlined net zero commitments and 20 had now set out plans to adapt and become more resilient to rising temperatures and their impacts.
But despite these commitments, Mr Sharma said not enough had been achieved.
"Have we made any real progress at this summit? And the answer to that is: yes," he said.
"But they will also ask, have we done enough to put the world on track to limit warming to 1.5C, and protect people and nature from the effects of climate change? To make the Paris Agreement a reality.
"Friends, we must be honest with ourselves, the answer to that, is currently: no. As encouraging as all this ambition is. It is not enough."
Mr Sharma re-stated a commitment made last year to double the UK's international climate finance spend. This will bring it to at least £11.6bn over the next five years.
Earlier on Saturday, UK Prime Minister Mr Johnson said advances in renewable energy technologies would "save our planet and create millions of high-skilled jobs".
He added: "Together we can use scientific advances to protect our entire planet - our biosphere - against a challenge far worse, far more destructive even than the coronavirus. And by the promethean power of our invention, we can begin to defend the Earth against the disaster of global warming."
Meanwhile, UN Secretary General António Guterres criticised rich countries for spending 50% more of their pandemic recovery cash on fossil fuels compared to low-carbon energy.
Mr Guterres said that 38 countries had already declared a climate emergency and he called on leaders worldwide to now do the same.
On Covid recovery spending, he said that this is money being borrowed from future generations.
"We cannot use these resources to lock in policies that burden future generations with a mountain of debt on a broken planet," he said.
The meeting is taking place after the pandemic caused the postponement of the annual Conference of the Parties (COP) meeting, which had been due to take place in Glasgow this year.
The UK has announced an end to support for overseas fossil fuel projects, and has today deposited a new climate plan with the UN.
It's the first time that Britain has had to do this, as it was previously covered by the European Union's climate commitments.
The UK pointed to its new commitment on overseas fossil fuel projects as well as a new carbon cutting target of 68% by 2030, announced last week by the prime minister.
The EU presented a new 2030 target of a 55% cut in emissions, agreed after all-night negotiations this week. Ursula von der Leyen, President of the European Commission, said: "It is the go-ahead for scaling up climate action across our economy and society."
China's President Xi Jinping announced that the country would reduce its carbon emissions per unit of gross domestic product (GDP) by over 65% compared with 2005 levels. China will also increase the share of non-fossil fuels in primary energy consumption by about 25%. And President Xi pledged to increase forest cover and boost wind and solar capacity.
But Manish Bapna, managing director of the World Resources Institute (WRI) said: "The strengthened renewable energy, carbon intensity, and forest targets are steps in the right direction, but recent WRI analysis shows that China would benefit more economically and socially if it aims higher, including by peaking emissions as early as possible."
Although President Donald Trump pulled the US out of the Paris pact, the summit saw statements from the Republican governor of Massachusetts, Charlie Baker, and the Democrat governor of Michigan, Gretchen Whitmer, who said the US was "all-in" on tackling climate change.
Pope Francis said the Vatican had committed to reaching net zero emissions, similar to carbon neutrality, before 2050. "The time has come to change course. Let us not rob future generations of the hope for a better future," he said.
A number of big emitters, including Australia, Saudi Arabia, Russia and Mexico, did not take part, as their climate actions were not deemed ambitious enough.
Some observers believe this hard line on some countries is justified.
"From a kind of symbolic procedural point of view, it's good to have everybody on board," said Prof Heike Schroeder from the University of East Anglia.
"But from a proactive, creating some kind of sense of urgency approach, it also makes sense to say we only get to hear from you if you have something new to say."
The five years since the Paris agreement was adopted have been the warmest on record, according to the World Meteorological Organization (WMO), and emissions have continued to accrue in the atmosphere.
But many countries and businesses have started the process of decarbonisation in that time.
The progress they've made now needs to be acknowledged and encouraged, says former UN climate chief Christiana Figueres.
"That progress that's been seen in the real economy has to be reflected and incentivised further by those additional commitments," she said.
One area that yielded little progress at this meeting was the question of finance. Rich countries had promised to mobilise $100bn a year from 2020 under the Paris agreement - but the commitments on cash are not forthcoming.
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