Climate strike – live: Millions across world demand urgent action to save planet in largest environmental protest in history

Some student protesters made excellent use of humour to promote their message on their placards. Here's Sabrina Barr with a roundup of the best signs from around the world:

Activists are staging small scale demonstrations in several German cities.

Police said several dozen activists blocked a road in the heart of Frankfurt, Germany's financial capital, on Friday morning. In Berlin, protesters blocked a bridge across the river Spree.

Organizers said more than 500 events are planned across Germany.

Under pressure from sustained protests over the past months, the government of Angela Merkel is planning to announce a package of measures to reduce Germany's greenhouse gas emissions later on Friday.

Despite big investments in renewable energy that made up 46 per cent of the country's electricity production in the second quarter of 2019, Germany is on course to miss its emissions reduction targets for 2020 by a wide margin.

Protesters are grouping in Victoria Tower Gardens from both directions, Phoebe Weston reports.

There is a loud speaker booming into the park with organisers encouraging people to make noise and chant. 

They said there are hundreds of thousands of people.

It was a very positive atmosphere and there were loads of children present.

In the park there are bands, choral singers and even a meditation tent.

More than 30 heads of state and government have signed an appeal for greater action to fight climate change circulated by Alexander Van der Bellen, Australia's president, ahead of next week's conference on global warming at the UN.

The Initiative for more Climate Ambition declares climate change the "key challenge of our time," adding "our generation is the first to experience the rapid increase in temperatures around the globe and probably the last with the opportunity to effectively combat an impending global climate crisis."

It said countries need to act "jointly, decisively and swiftly".

German president Frank-Walter Steinmeier's office said he was among the signatories, others of whom included Emmanuel Macron, the French president, Reuven Rivlin, his Israeli counterpart, and Mark Rutte, prime minister of the Netherlands.

A number of migrant charities and people linking climate justice with social justice are in attendance, Phoebe Weston reports.

Underlying the fight for the climate is a broader message about social equality and protecting the right to life for future generations.

It’s a very welcoming event and everyone I have spoken to is keen to talk and friendly.

There are lots of posters saying "stand up to racism" and "refugees welcome here". There is a big Extinction Rebellion presence along with groups protesting about people using plastic.

Thousands of protesters, including hundreds of children, gathered in Birmingham's Victoria Square before marching through nearby streets.

Addressing around 3,000 demonstrators in the square, Green Party councillor Julien Pritchard described those attending as an inspiration.

"To tackle the climate emergency means climate justice - we need a just transition," Mr Pritchard said. "We need to do it in a way which takes communities with us, which creates jobs, that takes people out of fuel poverty.

"But declaring a climate emergency is not enough - with national government doing so little it is vital that councils and Birmingham City Council step up to make meaningful action on climate change happen."

Meanwhile, West Mercia Police advised drivers to find alternatives routes after around 40 Extinction Rebellion members intermittently blocked traffic in Worcester.

Around 50 people in Hong Kong are protesting about climate change after a summer of pro-democracy demonstrations in the city.

Carrying banners and posters, they chanted "stop the pollution" as they marched along the harbor front.

Organiser Dhanada Mishra, a visiting scholar at the Hong Kong University of Science and Technology, said the younger generations will be seriously affected when the impacts of climate change are felt in the coming decade and beyond.

He said it was appropriate that young people should speak out and demand their future is not jeopardised by government inaction.

Protester Nayla Ventura said it was only fair to show her two children that it is OK for them to fight for their future.

Thousands of protesters, including hundreds of children, many wearing school uniform, gathered in Birmingham's Victoria Square before marching through nearby streets.

Addressing around 3,000 demonstrators in the square, Green Party councillor Julien Pritchard described those attending as an inspiration.

Mr Pritchard, who represents Birmingham's Druids Heath and Monyhull ward, said: "To tackle the climate emergency means climate justice - we need a just transition. We need to do it in a way which takes communities with us, which creates jobs, that takes people out of fuel poverty.

"But declaring a climate emergency is not enough - with national government doing so little it is vital that councils and Birmingham City Council step up to make meaningful action on climate change happen."

Here's an infographic from Statista showing how the oceans are heating up: 

Hundreds of people have marched in some African cities to highlight the dangers of climate change.

Banners in Kenya's capital, Nairobi, ranged from angry to playful, with one reading: "This planet is getting hotter than my imaginary boyfriend."

Other climate protests — part of a global strike on Friday ahead of a United Nations climate summit — are taking place in Johannesburg and the South African capital, Pretoria.

The hundreds of people gathered in Johannesburg chanted and waved signs saying "Climate justice now" and "There's only one Earth."

Experts say Africa is the most vulnerable continent to climate change and the least equipped to deal with it. Governments have pleaded for more support from the international community.