The protest, organized by Fridays for Future Toronto, is one of many Global Day of Climate Action demonstrations taking place all over the world today, including in other Canadian cities such as Halifax and Vancouver.
The demonstration, organised by the Fridays For Future movement, was part of a series of world-wide protests that were expected to be confined to small gatherings and online activism due to the COVID-19 pandemic.
Climate strike organisers in Austria said that 6,000 people had attended a demonstration in the capital Vienna despite heavy rain and organisational hurdles posed by the Covid-19 pandemic. The group held the rally to call governments around the world to take action in environmental sustainability to avoid the impacts of climate change.
She is pictured standing on an ice floe holding a poster reading "Youth Strike for Climate" - in what the environmental campaign group said was the world's most northerly climate strike.
She said in a tweet on Thursday that the strikers will "be back next week, next month and next year. The climate crisis has never once been treated as a crisis and unless we treat it as a crisis we won't be able to, so-called, "solve" it", Thunberg told reporters.
They also pointed to the Indian and United Kingdom governments' labelling of climate-change activists as "terrorists".
Rally organiser Murphy McDonald-Smith said she had planned for only 10 people to turn up to the COVID-safe event, but more turned up after they heard about the event.
German climate activist Luisa Neubauer told the crowd, "We're here because we know that climate justice is possible as long as we keep fighting for it".
They demand that lawmakers stick to the 2015 landmark Paris climate deal that asks both rich and poor countries to take action to curb the rise in global temperatures that is melting glaciers, raising sea levels and shifting rainfall patterns.
Demonstrators clutched umbrellas and carried signs to highlight the climate crisis, while some scribbled messages on their face masks such as "Not a single degree more" and "Unite behind the science".
Greenpeace meanwhile marked the day by releasing a photo recently taken in the Arctic of 18-year-old ornithologist Mya-Rose Craig, known as "birdgirl".