Greta Thunberg has celebrated returning to Sweden after an epic four-month odyssey without using planes by posing with her pet dogs, Moses and Roxy.

The 16-year-old climate activist, who was joined by the golden retriever and black Labrador at Stockholm's harbour on Tuesday morning, captioned the photo: 'Home!'

Thunberg, who was recently named TIME magazine's 'Person of the Year', has been on a continent-spanning climate campaign since sailing to the UN conference in New York in August.

But after making it back for the COP25 climate summit in Madrid last week, Thunberg had a rocky journey home when she lashed out at Europe's largest rail operator.

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Greta Thunberg with Moses the golden retriever and Roxy the black Labrador at Stockholm's harbour on Tuesday morning, captioning the picture: 'Home!'

Thunberg's odyssey began when she set sail from Plymouth, England, on August 14 and arrived in New York at the end of that month. She then made her way across to Los Angeles preparing to journey to Chile for the COP25. But her plans changed when the conference was moved to Madrid and she sailed from Hampton, Virginia on November 13 and arrived in Lisbon, Portugal on December 3

The teen was locked in a Twitter spat over the weekend when she shared a photo of herself sitting on the floor of a train carriage heading through Germany.

Thunberg's transatlantic odyssey August 14: Sets sail from Plymouth, England. August 28: Arrives in New York, USA. She takes in Washington, D.C. Montreal, Quebec, Iowa City, Iowa, Standing Rock Indian Reservation, South Dakota, Denver, Colorado, Vancouver, British Columbia, and finally Los Angeles, California. She had planned to travel south to Chile for the COP25 climate summit but because of political unrest it was relocated to Madrid. 'It turns out I’ve traveled half around the world, the wrong way,' she tweeted in November. November 13: Sets sail from Hampton, Virginia. December 3: Arrives in Lisbon, Portugal. December 9: Takes part in a massive rally in Madrid for COP25. December 13: Fridays for Future protest in Turin, Italy. December 14: Train from Basel, Switzerland, north through Germany. December 17: Posts photo with her dogs in Stockholm ('Home!') Advertisement

Deutsche Bahn reacted sarcastically to her apparent complaint about 'overcrowding,' and reliably informed the world that Thunberg had been upgraded to First Class.

Thunberg had written on Saturday: 'Traveling on overcrowded trains through Germany. And I’m finally on my way home!'

In a stinging reply, DB said: 'Dear #Greta, thank you for supporting us railroad workers in the fight against climate change! We were pleased that you were on the ICE (Inter City Express) 74 with us on Saturday. And with 100 percent green electricity.

'It would have been even nicer if you had also reported how friendly and competent you were looked after by our team at your seat in first class.'

Thunberg swiftly replied: 'Our train from Basel was taken out of traffic. So we sat on the floor on 2 different trains. After Göttingen I got a seat. This is no problem of course and I never said it was.

'Overcrowded trains is a great sign because it means the demand for train travel is high!'

DB followed up their tweets with a press release, in which they added that Greta's travel companions 'were sitting in first class from Frankfurt onwards'.

Her online run-in with DB came just a day after she had spoken before a furious climate protest in Turin, Italy, and said that she would 'put world leaders against the wall' if they continued running away from their climate obligations.

Thunberg, who most recently attended the COP25 climate summit Madrid, had a rocky journey home after she lashed out at Europe's largest rail operator on Saturday, tweeting that she had been an 'overcrowded' train through Germany

Deutsche Bahn replied to Thunberg's tweets and revealed that she had been upgraded to First Class

She later apologised for the remark, made after the summit in Madrid, claiming that a Swedish phrase had been lost in translation.

Thunberg created a storm in Turin on Friday when she said she would 'put world leaders against the wall' if they shirked their responsibilities on climate change

'Yesterday I said we must hold our leaders accountable and unfortunately said "put them against the wall". That's Swenglish: 'att ställa någon mot väggen' (to put someone against the wall) means to hold someone accountable. That's what happens when you improvise speeches in a second language.' Ms Thunberg wrote.

'But of course I apologise if anyone misunderstood this. I can not enough express the fact that I - as well as the entire school strike movement - are against any possible form of violence. It goes without saying but I say it anyway.'

And that followed on the heels of another high-profile Twitter storm after Thunberg was named TIME's 'Person of the Year.'

President Donald Trump - who was given the accolade in 2016 - tweeted that she had 'anger management problems' and told her to 'chill'.

Thunberg responded by changing her Twitter bio to include the words 'currently chilling'.

Thunberg docked at the North Cove Marina near the World Trade Center in Manhattan on arrival in August

Greta Thunberg told cheering protesters Friday 'we will make sure we put world leaders against the wall' if they fail to take urgent action on climate change

Thunberg's journey through Germany was the last leg of a continent-spanning trip which began when she travelled to New York on a low-emissions yacht in August.

Th 16-year-old activist started a worldwide movement last year when she began to strike from school every Friday to protest government inaction on climate change.

Refusing to fly, she has twice crossed the Atlantic by boat in recent months in order to speak at a UN climate summit in New York and the hastily rearranged COP25 summit in Madrid.