Teenage activist Greta Thunberg said today that activists' calls on the corporate and political elite at Davos to seriously fight climate change had been "completely ignored".
But she vowed not to be subdued by stinging personal criticism from the Trump administration.
The 50th edition of the annual Swiss Alps forum wrapped up with the menace of climate change hammered into the minds of participants but doubt over whether any concrete action would be forthcoming.
UN Secretary General Antonio Guterres warned at Davos this year that climate change could leave humanity "doomed".
Thunberg, whose school strike movement had inspired a generation of young people to pressure governments over their inaction, had told the World Economic Forum she wanted to see an end to investment in fossil fuels.
"Before we came here we had a few demands for this WEF. Of course these demands have been completely ignored. We expected nothing less," Thunberg told reporters in the ski resort on the last day of the conference.
"As long as the science is being ignored - as the facts are not being taken into account - and as long as the situation is not being treated as a crisis, then world and business leaders can, of course, continue to ignore the situation," she said.
"They do not have to do anything as they are not being held accountable," she lamented before joining other young people in one of her regular "Fridays for Future" protests in Davos.
Greta Thunberg has been taking part in a climate demonstration in Davos as the World Economic Forum draws to a close. The teenage activist said her pleas for an end to the use of fossil fuels had been ignored. @willgoodbody reports | https://t.co/ICK2LrqTUs pic.twitter.com/8xE6yuVlnT— RTÉ News (@rtenews) January 24, 2020
The Swede had emerged as one of the key figures of the Davos forum, warning "our house is still on fire" and prompting US President Donald Trump to grumble on his visit to the event about the "perennial prophets of doom".
Her demand for an immediate halt to investment in fossil fuels also prompted a stingingly personal aside from US Treasury Secretary Steven Mnuchin yesterday.
"Is she the chief economist? Who is she? I'm confused," Mnuchin said, emphasising after a pause that this was a joke.
"After she goes and studies economics in college, she can come back and explain that to us," he said.
Asked about Mnuchin's comments, the Swede said: "Of course it has no effect. We are being criticised like that all the time."
"If we cared about that, we would not be able to do what we do. We put ourselves in the spotlight," she added.
Steve Mnuchin today launched a new defence of US policy, insisting the Trump administration cared for the environment, but that problems should not be reduced to just climate change.
"Climate change is one of many issues" affecting the environment, he said, adding Trump was a firm advocate of "clean air and clean water."
He said the reason the US left the Paris climate agreement - which calls for blocking global warming at well below 2C, and 1.5C if possible - "was not because we don't support the environment (but because) we thought it wasn't a fair and balanced agreement."
He added that there were other key global issues to worry about, notably that "there's way too many people in the developing world" without access to electricity and preventing the spread of epidemics in the next decades like the coronavirus.
The starkest warnings at the forum came from Britain's Prince Charles - who asked "what good is all the extra wealth in the world... if you can do nothing with it, except watch it burn?" - and Guterres.
The UN chief warned that the world was losing the war against climate change and humanity's capacity "to live in this planet" will risk being destroyed.
"We need to act in order to make sure we are not doomed," he said.
Another prominent climate change protest leader, German student Luisa Neubauer, acknowledged that some bold words had been heard at Davos, but deeds were now needed.
"We never striked for discourse change," said Neubauer, who this month turned down the offer of a board seat on a subsidiary of German industrial giant Siemens.
"From the first day onward, we striked for actual climate action," she added.