United States climate envoy John Kerry said on Monday that the COP 26 climate summit in Glasgow had opened a new phase of "accountability" in the world's battle against climate change.

Nearly 200 nations on Saturday signed a deal to try to halt runaway global warming after two weeks of painful negotiations, but fell short of what scientists say is needed to contain dangerous rises.

Speaking at an environmental conference in Paris, Kerry said he was "a little bit shocked" at negative media reports about the Glasgow meeting's outcome, calling them "cataclysmic" and showing a lack of understanding of the COP process.

"Nobody expected that in Glasgow the issue was going to be gone. Nobody thought Glasgow was going to wipe it away," he said.

But the conference had opened a "new era of accountability" that would now be carried over into the next COP meeting in Egypt next year, he said.

Participants had created "a clear pathway with rules, with transparency requirements", he said.

COP host British Prime Minister Boris Johnson on Sunday hailed the conference's accord as "truly historic", adding that his joy was "tinged with disappointment" because not all countries agreed to phase out hydrocarbons.

Stepping up

But Kerry said that "the ambition is higher than anybody thought it could be". 

He said "a whole bunch of countries that were not willing to do anything are now stepping up to do real things".

He said the alternative to the deal that was reached "was to leave Glasgow with nothing".

Kerry said huge financial investments were now needed to rein in climate change, including into new technology which he said was a "critical component" in the battle to limit global warming.

But since "no country in the world has enough money to make this happen", Kerry said, "the only way to achieve sufficient financing is by bringing the private sector to the table in a massive way and that clearly began to happen in Glasgow".

Kerry said plans by major financial institutions and large industrial companies for climate-friendly investment had already reached unprecedented levels.

"For the first time ever, we really do have trillions of dollars dedicated to climate investment," Kerry said.

"We can harness this and my hope that businesses around the world will see the opportunity."

Future benefits also included "a safer, healthier, and cleaner world in which our kids and grandkids can inherit something that lives up to our moral obligation", Kerry said.

Scientists have already warned that the deals struck under the "Glasgow Pact" will not result in limiting global warming to 1.5 degrees Celsius above pre-industrial levels, the most ambitious objective of the 2015 Paris Agreement.

But it was first time after 25 previous conferences that the words "fossil fuels" and "coal" -- the main culprits of global warming -- have made it into the final text.

India and China managed at the last moment to soften the wording to "phase down" instead of "phase out".