US President Donald Trump dismissed the concerns of environmental activists as "pessimism" in a speech to political and business leaders at the start of the World Economic Forum (WEF) in Davos on Tuesday.

Climate change and global warming are topping the agenda at this year's annual meeting in the Swiss ski resort of Davos, with activists at odds with businesses and governments about how to tackle the issue.

What Trump said:

The US leader dubbed climate activists "prophets of doom" and rejected their warnings, saying: "Fear and doubt is not a good thought process."

Despite concerns about emissions, Trump praised the US as one of the world's largest producers of natural gas.

He announced that the US would be joining the WEF's 1 trillion trees initiative.

When asked about his stance on climate change by reporters ahead of his speech, he said: "I'm a big believer in the environment. The environment is very important to me."

Much of Trump's speech focused on praising his administration's domestic economic policies, saying that by rolling back regulations, prosperity "would come thundering back at record speed."

"A nation's highest duty is to its own citizens," he said. "Only when governments put their citizens first, will they be invested in their national futures."

Read more: Social entrepreneurs meet at World Economic Forum in Davos

Climate activists march to World Economic Forum in Davos Big flack: McDonald's a target of the activists' criticism Some of the protesters dressed as Ronald McDonald, the character that represents the world renowned fast-food chain. McDonald's has borne the brunt of severe criticism due to being viewed as the epicenter of mass produced food and is one of the largest buyers of beef in the world, an industry that has been targeted by climate activists in the past.

Climate activists march to World Economic Forum in Davos Trump accusations Donald Trump did not escape the ire of the activists as they began their march to the annual World Economic Forum in Davos. The 2020 event will convene nearly 3,000 participants from over 100 countries, including 53 heads of state, among them the US President and German Chancellor Angela Merkel. The protesters are angry that these global figures are not doing enough to combat global warming.

Climate activists march to World Economic Forum in Davos Taking the lead A man holds a placard suggesting the World Economic Forum needs to be led, and not be the leader, as he takes part in a gathering called by climate activists prior to the start of a march to Davos, where the financial meeting begins on January 22. The hike began in Landquart, in eastern Switzerland and will arrive at the ski resort three days later.

Climate activists march to World Economic Forum in Davos Eco responsibility People hold placards, many of which have warnings of the ecological repercussions of the actions of humans, as they participate in a gathering called by climate activists prior to the start of a march to Davos. A recent study reported that the world's oceans are warming at an alarming rate, which will most likely contribute to more land crises such as the bushfires currently devastating Australia.

Climate activists march to World Economic Forum in Davos 'Strike for the climate' A woman wears a hat with a badge reading "strike for the climate" as the crowds gathered at the beginning of the hike. The phrase has become synonymous with Greta Thunberg and her climate change movement that began 18 months ago. Author: John Silk



Greta: 'Basically nothing has been done'

Following Trump's speech, Swedish teen climate activist Greta Thunberg criticized world leaders and business executives for failing to meet their climate targets.

"Unlike you, my generation will not give up without a fight. The facts are clear but they are still too uncomfortable for you to address," she told a panel.

"Our house is still on fire. Your inaction is fueling the flames by the hour. And we are telling you to act as if you loved your children above all else," Thunberg said, echoing her remarks from her WEF appearance last year.

At a panel just before Trump arrived, Thunberg emphasized that moderate changes will not be enough to slow the impact 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.

Read more: Davos medical tourism sparks alarm about corporate culture

'There is a difference between being heard to actually leading to something,' Thunberg said at the start of the WEF

Who else will be there? Over 50 heads of state and government will be in attendance along with over 3,000 other participants. German Chancellor Angela Merkel is due to speak on Thursday. Following in Thunberg's footsteps, other young activists are also taking part this year, including South African climate activist Ayakha Melithafa and Irish teen scientist Fionn Ferreira.

What to look out for: It will be the first time that Trump meets with the new European Commission president, Ursula von der Leyen. The US leader has repeatedly clashed with the EU over trade and tax policies. It also remains to be seen whether businesses will back up their pledges on climate change with concrete action.

What is Davos? It's the 50th meeting of the World Economic Forum this year, which was launched by German economist Klaus Schwab. The meeting takes place at the Swiss ski resort of Davos, drawing world leaders, business executives, academics, charity heads and celebrities. The conference is used to hold bilateral meetings, make business deals or to try and impact the global agenda. The meeting this year runs from January 21 – 24.

Watch video 02:29 Share Social entrepreneurs and fair trade in Davos Send Facebook google+ Whatsapp Tumblr linkedin stumble Digg reddit Newsvine Permalink https://p.dw.com/p/3WVov Social entrepreneurs bring fair trade spirit to Davos

rs/rt (AFP, AP, Reuters)

Every evening, DW sends out a selection of the day's news and features. Sign up here.