Swedish climate activist Greta Thunberg has told the annual elite Davos gathering of business and political leaders that "basically nothing has been done" to fight climate change despite her high-profile campaign.

The 50th meeting of the World Economic Forum in the Swiss Alps resort got under way seeking to meet head-on the dangers to both the environment and economy from the heating of the planet.

US President Donald Trump gave the first keynote address of Davos 2020.

But before his appearance, Greta underlined the message that has inspired millions around the world - that governments are failing to wake up to the reality of climate change.

"We are all fighting for the environment and climate. If you see it from a bigger perspective, basically nothing has been done.

"It will require much more than this. This is just the very beginning," she said.

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She acknowledged that her campaign which began with school strikes had attracted huge attention without yet achieving change.

"There is a difference between being heard to actually leading to something," she said.

"I am not the person who should complain about not being heard," she said to appreciative laughter.

"I am being heard all the time. But the science and the voice of the young people are not at the centre of the conversation," she added.

The forum's own Global Risks report published last week warned that "climate change is striking harder and more rapidly than many expected" with global temperatures on track to increase by at least 3C (5.4F) towards the end of the century.

There are no expectations that Mr Trump and Greta Thunberg, who have exchanged barbs through Twitter, will actually meet, but the crowded venue and intense schedule mean a chance encounter cannot be ruled out.

When Mr Trump and his entourage walked through UN headquarters last year at the annual General Assembly, a photo of the teenager staring in apparent fury at the president from the sidelines went viral.

Sustainability is the buzzword at the forum, which began in 1971, with heel crampons handed out to participants to encourage them to walk on the icy streets rather than use cars, and the signage paint made out of seaweed.

Business leaders attending the forum will be keen to tout their awareness on climate change but are likely also to be concerned by the state of the global economy whose prospects, according to the IMF, have improved but remain brittle.

The IMF cut its global growth estimate for 2020 to 3.3%, saying that a recent truce in the trade war between China and the US had brought some stability but that risks remained.

"We are already seeing some tentative signs of stabilisation but we have not reached a turning point yet," said IMF chief Kristalina Georgieva.

Activists, meanwhile, will be pressing for much more concrete action to fight inequality, after Oxfam issued a report outlining how the number of billionaires has doubled in the past decade and the world's 22 richest men now have more wealth than all the women in Africa.

Greenpeace, meanwhile, complained that some of the world's biggest banks, insurers and pension funds have collectively invested $1.4 trillion in fossil fuel companies since the Paris climate deal.

Other key priorities will be exploring how to battle biodiversity loss, narrow the digital divide between the internet haves and have nots and step up the fight against pandemics in the face of vaccine hesitancy and drug resistance.

"I am angry about the state of the world but I am also determined to engage and provide solutions and deliver," WWF director general Marco Lambertini told AFP. "There needs to be healthy balance between these two sentiments."

Ireland was due to be represented by Taoiseach Leo Varadkar, Tánaiste and Minister for Foreign Affairs Simon Coveney and Minister for Finance Paschal Donohoe. 

However, none of the three have travelled because of the General Election.