It may be easy to describe the new U.S. president as unpredictable, and certainly as unco-operative in some global affairs, but during his lengthy time in the public eye, he has demonstrated two consistent qualities: Donald Trump does things his own way and doesn't like to lose.

While that combination may have helped him become leader of the free world, it easily set him apart at Trump's first G20 summit, in Hamburg, Germany.

Given his opposition to addressing environmental concerns, critics quickly cast him as the Grinch who stole the Paris Agreement on climate change.

German Chancellor Angela Merkel confirmed talks around climate change were difficult, as had been expected.

But at a time when Trump's decision to withdraw from the agreement could have become an excuse for world leaders to ease off on their own commitments, all other G20 countries made a distinct choice not to waver.

Canada's Prime Minister tried to put a positive spin on fighting climate change, without Trump on board.

"I believe that the fact that we stayed strong in terms of 19 countries that are solidly committed, realizing that the United States made a different choice for the time being, but at the same time, pointing out that in terms of U.S. states and municipalities and the big corporations in the United States, we still see that there is that strong desire to join the fight against climate change," Trudeau said at a news conference Saturday afternoon.

Merkel made similar comments in her closing statement, adding that in no way are leaders trying to hide, or paper over the deep divide on the issue.

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If that wasn't enough tension, Trump's daughter raised eyebrows with critics when she sat in her father's chair — unaware of protocol or ignoring it — at a table where G20 leaders held a working session on African migration and health.

The U.S. president had left the closed-door session for a bilateral meeting midday Saturday, when Ivanka Trump took his seat between British Prime Minister Teresa May and Chinese President Xi Jinping.

It was not the usual setup for a first daughter, as typically senior bureaucrats or cabinet ministers would substitute for a leader taking time out.

Word spread quickly on social media about the move after a Russian diplomat tweeted a picture of the table. Hours later, the tweet was deleted after criticism emerged online and at the meeting centre.

Being odd man out may have affronted the U.S. president. At the last minute, he cancelled his closing news conference, leaving an awkward scene of international media capturing only the dismantling of the setup for his remarks.

Academics who study these summits closely suggest Trump may learn something from this summit experience that he can take forward.

"We always have a chance next year," said John Kirton, director of the G7 Research Group at the University of Toronto.

At least then, he says, Trump will "have more time on the job, will have more time to learn if you control climate change you're saving a lot of lives in the United States."

But Trump has shown, even amid disapproval, little indication he will be changing things up dramatically, so perhaps G20 leaders will end up continuing down their own path on which they've started.

Trump Whisperer or not

Even if G20 leaders were not able to get Donald Trump on side with some key priorities, Trudeau is walking away from the summit with one small comfort.

The U.S. president seems to actually like him. A lot. At least for now.

"We have a great neighbour in Canada and Justin is doing a spectacular job," Trump said during an announcement on funding to empower women in developing countries.

"Everybody loves him and they love him for a reason, so congratulations."

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Canada's Prime Minister Justin Trudeau, left, talks to U.S. President Donald Trump at the G20 summit in Hamburg on Saturday. (Michael Sohn/Associated Press)

Pundits had mused that Trudeau could be an intermediary between Trump and European leaders who have not experienced the same warm start to their professional relationship.

Canada's foreign minister, Chrystia Freeland, said Trudeau took on a leadership role, but downplayed the so-called "Trump Whisperer" concept — a label offered in jest by the New York Times White House chief correspondent in a recent interview with Trudeau.

"Our European partners are incredibly effective international diplomats," Freeland told reporters.

"I think it would be a mistake for Trudeau to say I'm the interlocutor here," said Thomas Bernes, a CIGI fellow and former executive at the IMF.

"That risks creating expectations that can't be fulfilled," he added.

Lack of access

The G20 was the last stop for Trudeau on a six-day tour of the U.K. and Europe.

While the prime minister held daily photo opportunities, there were only two news conferences which happened to bookend his trip.

On Tuesday, Trudeau's first full day in Ireland, he held a joint media availability with the new Irish Prime Minister Leo Varadkar. At that event, Canadian journalists and Irish reporters were each granted three questions.

Trudeau did not hold another availability until Saturday, at the closing of the G20 summit.

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Prime Minister Justin Trudeau speaks to the media during his closing news conference at the G20 summit Saturday in Hamburg. (Ryan Remiorz/Canadian Press)

Reporters were also told Canadian officials working on the G20 negotiating team did not have time in their schedule to discuss Canada's goals at the summit.

Typically ahead of a big international meeting like this, reporters are given an in-depth briefing by "sherpas," the top level officials doing the heavy lifting behind the scenes. This is done in addition to on the record interviews with Canadian politicians attending the summit.

Instead, Freeland took some reporter questions on Friday of the summit, while Finance Minister Bill Morneau answered questions on Saturday.

International celebrity

This overseas visit reaffirms something that frustrates the official opposition and critics: Justin Trudeau is an international celebrity.

It is not an opinion, it is a simple fact.

In Ireland, Scotland, and Germany adoring strangers asked the prime minister for selfies. But the effusive praise also came from other world leaders.

"For the Canadians, you are all so lucky to have this man as prime minister. He has brought an incredible breath of fresh air, directness, commitment to the issues," gushed World Bank President Jim Yong Kim during their meeting at the Global Citizen concert in Hamburg.

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Prime Minister Justin Trudeau was a hit with the crowd at the Global Citizen concert in Hamburg. (Ryan Remiorz/Canadian Press)

When Trudeau was introduced to the 12,000 mostly young adults at that social activism music festival, he received applause that almost matched cheers for headliners Coldplay.

Whether the excited crowd was interested in his message of empowering women, or took interest in Trudeau for other reasons, his appearance was well-received. The mayor of Hamburg had a far more difficult appearance at the show, as he was booed by the crowd.

Trudeau's staff are also getting international recognition. This picture of Trudeau's executive assistant, Tommy Desfosses, carrying gifts for the prime minister was a hit in the Irish press. Desfosses was then featured in light hearted news articles around the world, musing whether he is "cuter" than the prime minister.

Trudeau's young son, who accompanied his parents overseas, also became a darling of the international press.

Three-year-old Hadrien's joyful jumping down the stairs of the plane to the tarmac was repeated on newscasts around the world.

But it is a photo taken by the Prime Minister's official photographer that received the most attention. Adam Scotti was trying to get a shot of Trudeau meeting with the German welcome delegation in Hamburg. Instead, Hadrien posed for a photobomb that lit up the internet.