On the seventh day of demonstrations that have occupied key spots in the British capital, Swedish teenage climate activist Greta Thunberg addressed the demonstrators, telling them: "Humanity is standing at a crossroads."
Organizers said they were willing to switch tactics from disruption to dialogue next week - if the government enters talks.
"We are prepared to pause, should the government come to the negotiating table," Extinction Rebellion spokesman James Fox told AFP. "What the pause looks like is us stopping an escalation. We can discuss leaving if they are willing to discuss our demands. At the moment, we haven't received a response from the government... so we're waiting on that."
Extinction Rebellion was established last year in Britain by academics and has become one of the world's fastest-growing environmental movements.
Campaigners want governments to declare a climate and ecological emergency, reduce greenhouse gas emissions to zero by 2025, halt biodiversity loss and be led by new "citizens' assemblies on climate and ecological justice.
"We're giving them an opportunity now to come and speak to us," Fox told AFP. "If they refuse to come and negotiate with us, then this is going to continue and this is going to escalate in different, diverse and very creative ways."
Thunberg, the 16-year-old activist who has inspired pupils worldwide to boycott classes to join climate protests, addressed the cheering crowds at the Marble Arch landmark, the only authorized demonstration site.
"For way too long the politicians and people in power have got away with not doing anything at all to fight the climate crisis and ecological crisis," she said. "But we will make sure that they will not get away with it any longer."
She continued: "How do we want the future living conditions for all living species to be like? Humanity is now standing at a crossroads. We must now decide which path we want to take. We are waiting for the others to follow our example."
Police said they had managed to clear the protesters from Parliament Square and the Oxford Circus and Piccadilly Circus junctions.
Those charged range in age from 19 to 77. They hail from around England and Wales, with one person from France charged.
The charges are for various offenses including breaching public order laws, obstructing a highway and obstructing police.
Calling for an end to the protests, London Mayor Sadiq Khan said more than 9,000 police officers had been responding to the demonstrations, which had left the force as a whole overstretched.
"This is now taking a real toll on our city... this is counter-productive to the cause," he said. "You must now let London return to business as usual."
In the blazing sunshine on Waterloo Bridge, police lifted protesters and carried them off to waiting police vans.
"I'm genuinely terrified. I think about it all the time. I'm so scared for the world. I feel like there is going to be calamity in my lifetime," student Amber Gray told AFP. "I don't even feel comfortable bringing children into this world knowing that that is coming. And I don't want people in the future to say to me, 'why didn't you do anything?'."