The climate crisis was in focus as activists and critics collided at the World Economic Forum in the snowy Alpine ski resort of Davos, Switzerland.
Overheated markets, space and trade deals were also on the agenda as the world's political and business leaders convened at this year's summit.
U.S. President Donald Trump likened Elon Musk to inventor Thomas Edison, calling the CEO of Tesla and SpaceX one of the world's "great geniuses."
He told CNBC's Joe Kernen in an interview that "we have to protect our genius."
"You know, we have to protect Thomas Edison and we have to protect all of these people that came up with originally the light bulb and the wheel and all of these things. And he's one of our very smart people and we want to cherish those people," the president said.
Trump's comments came after a recent surge in Tesla's shares, which have more than doubled since September.
Liberal billionaire George Soros took aim at Trump, warning that the U.S. economy could be headed for calamity as a result of the president's efforts to juice American business and stock prices ahead of the 2020 election.
"The stock market, already celebrating Trump's military success, is breaking out to reach new heights," he told guests at an informal dinner in Davos. "But an overheated economy can't be kept boiling for too long. If all this had happened closer to the elections, it would have assured his reelection."
"His problem is that the elections are still 10 months away, and in a revolutionary situation, that is a lifetime," Soros said.
German Chancellor Angela Merkel warned business and political leaders that the conflict in Libya could have similar ramifications to the war in Syria.
"We have to be vigilant," she said, suggesting that the continuing battles in the North African country could result in a similar swathe of refugees fleeing conflict and coming to Europe, as has been the case with Syria in the past five years.
Teenage activist Greta Thunberg reiterated her message on the climate crisis from last year's forum, telling leaders that "our house is still on fire" and that their inaction was "fueling the flames by the hour."
The 17-year-old Swede exhorted the WEF audience to "act as if you loved your children above all else."
Thunberg said companies and governments would have to comply with cutting emissions and divesting from fossil fuels or be forced to explain to their children why they were giving up on the global warming target of 1.5 degrees Celsius "without even trying."
"Unlike you, my generation will not give up without a fight," she said.
U.S. Treasury Secretary Steven Mnuchin criticized Thunberg's credentials, saying the 17-year-old should study economics at college before lecturing the U.S. on fossil fuel investments.
"Is she the chief economist or who is she? I'm confused," Mnuchin said at a press briefing, before adding this was "a joke. That was funny."
In response to Mnuchin, Thunberg said Thursday that "it doesn't take a college degree in economics" to understand ongoing fossil fuel subsidies and our remaining carbon budget "don't add up."
Former U.S. Vice President Al Gore compared the climate crisis to historic events like the 9/11 terrorist attacks.
He said the crisis was "way worse" than many realize and intensifying "way faster" than people appreciated and described it as a "challenge to our moral imagination."
"This is Thermopylae. This is Agincourt. This is Dunkirk. This is the Battle of the Bulge. This is 9/11," he added.
The U.K.'s priority is to strike a trade deal with the European Union ahead of the U.S., the country's Finance Minister Sajid Javid said.
Javid was speaking on CNBC's "Future of Financial Markets" panel alongside Mnuchin, IMF Managing Director Kristalina Georgieva and UBS Chairman Axel Weber.
The finance minister's comments came after Mnuchin said the U.S. was a "bit disappointed" not to have been able to negotiate with the U.K. first.
The U.K. is due to leave the EU next Friday, and the government has set a deadline for a trade deal with the EU for the end of 2020, a short time frame that many officials in Europe see as unfeasible.
U.S. Commerce Secretary Wilbur Ross questioned whether a lack of agreed international rules concerning space exploration could inadvertently trigger a lawless "Wild West situation."
His comments come as a new era of space discovery gathers pace, with an ever-growing list of space agencies forming around the world.
"Who owns space? Who owns whatever we find? If you are the first one to the asteroid, does that mean you have a claim on all of the minerals in that asteroid?" Ross said.
Hong Kong leader Carrie Lam suggested possible foreign influence to be at work in the protests that have roiled the city-state over the last nine months.
"Well, I have no conclusive evidence to answer your question, but it is for all to see that what has happened in Hong Kong on this occasion has attracted disproportionate commentary from Western media, from overseas governments and politicians," she told CNBC's Geoff Cutmore, adding she felt there was "perhaps something at work."
Political tensions in Hong Kong have escalated over an extradition bill, which has now been dropped, that would have allowed those arrested in the territory to be sent to mainland China for trial.
Lebanon's former Foreign Minister Gebran Bassil told CNBC's Hadley Gamble he came to Davos "on his own expenses," in defense of his trip as the country faces economic collapse.
His presence at Davos drew widespread anger among Lebanese, with petitions to ban his participation at the elite event garnering tens of thousands of signatures.
"I know rumors and lies circulate always on issues like this, but I am used to this and this is the reality," Bassil said.
The prime minister of Finland, Sanna Marin, said she hoped that the election of female leaders will not get as much attention in the future but would be considered the "new normal."
Marin, 34, who became the world's youngest prime minister when she was inaugurated as Finland's leader in December, made her comments on a panel about gender equality.
But she also said it was important to realize the world was not always working in a progressive way, that "we all have to fight each and every day for equality, for a better life, as there are things happening in the world going backwards."
Billionaire investor Paul Tudor Jones said the stock market today is reminiscent of the latter stages of the bull market in 1999 that saw a giant surge but ended with the popping of the dot-com bubble.
"We are just again in this craziest monetary and fiscal mix in history. It's so explosive. It defies imagination," Jones said on CNBC's "Squawk Box."
Asked if investors should sell now to avoid a blow-up like the one that took place in March 2000, Jones said, "Not really. The train has got a long, long way to go if you think about it."
"Right now people think central banks around the world can do whatever they want. They can't," he told CNBC's Andrew Ross Sorkin. "They're intelligent, looking at all the facts trying to figure out what to do. But [inflation] would be the big negative surprise."
Ray Dalio, founder of investment firm Bridgewater Associates, said he thinks "cash is trash" and that investors shouldn't miss out on the strength of the current market.
"Everybody is missing out, so everybody wants to get in," Dalio said on CNBC's "Squawk Box."
Dalio advised having a global and well-diversified portfolio in this market and said the thing people can't "jump into" is cash.
—CNBC's Matthew J.Belvedere, Thomas Franck, Brian Schwartz, Silvia Amaro, Sam Meredith, Holly Ellyatt, Matt Clinch, Grace Shao, Natasha Turak, Yun Li and Michael Sheetz contributed to this article.