Tens of thousands stage world's largest climate march in Copenhagen

Tens of thousands of climate activists marched in Copenhagen yesterday as part of a worldwide "Day of Action" to urge negotiators at UN talks to agree a strong treaty to fight global warming.

The rally was mostly held in a carnival atmosphere, but riot police detained about 900 activists at the rear of the march after bottles were thrown and a window at the Danish foreign ministry was smashed. The activists were forced to sit down on the street, with hands tied behind their backs.

The number of people on the march was estimated at 25,000 by police and up to 100,000 by organisers. Banners read, "There is no planet B", and "Change the politics, not the climate". Some activists dressed as polar bears and penguins with signs reading: "Save the Humans!" Some held a giant inflatable snowman under threat of melting from warming caused by burning fossil fuels.

A Copenhagen police spokeswoman later confirmed that two Britons were deported for vandalism and spitting on a police officer during the protests. Police blamed the trouble on militant activist groups, and claimed the troublemakers included groups responsible for provoking violence during a Nato summit in the French city of Strasbourg last April.

The arrests came after the march from the city to the Bella Centre, where the UN Climate Change Conference is being held.

Taking part in the world's largest ever climate-change march, which was named The Flood, and organised by Friends of the Earth, were the supermodel turned activist Helena Christensen, Bollywood actor Rahul Bose, and British actress Helen Baxendale. Christensen said: "They will be very bad politicians if they do not hear us by now."

Protesters were demanding that negotiators strike a deal to prevent catastrophic levels of global warming. In the Global Day of Action, campaigners also staged events abroad, including a four-minute "flashdance" outside the Houses of Parliament, with volunteers across London collecting messages from citizens to give to MPs.

The Flood coincided with the arrival of environment ministers in Copenhagen yesterday for informal talks before world leaders join the summit later this week.

While government officials try to find some sort of compromise, health experts will warn this week of the potentially dire consequences of failure. The lives of hundreds of millions worldwide are being put at risk by climate change, with impacts escalating into the foreseeable future, warns a new report by the World Health Organisation being presented to delegates at the climate talks on Thursday.

Progress against diseases such as cholera, malaria and dengue fever could be reversed, says the Protecting Health from Climate Change report, which predicts that the population at risk of malaria in Africa could rise by 170 million by 2030, and the global population at risk of dengue by an extra two billion by the 2080s. "Climate change threatens the very fabric of global health," said Dr Diarmid Campbell-Lendrum, lead author of the report. He added: "We have a choice between a world that is more dangerous, worse for health and more degraded and unfair, and one that is more sustainable, equitable and beneficial for health."

The warning comes as climate experts stress that countries will need to go beyond the deals already on the table just to have a reasonable chance of containing warming at below C.

Lord Stern, chair of the Grantham Research Institute on Climate Change, said: "A deal that puts us on the path to having a good chance of avoiding warming of C, is possible – but ... we need to capture the high end of those proposals and more in Copenhagen, and then ratchet up commitments."

An alternative summit in Copenhagen claims to have the answer. A proposal from Klimaforum09 – representing 70 organisations from 92 countries – calling for a "system change" to a carbon-free economy by 2040 will be presented to government delegations on Tuesday. It rejects "false solutions" such as nuclear energy and argues for the "safe, clean, renewable and sustainable use of natural resources".

One of those backing the declaration, the Indian environmentalist Dr Vandana Shiva, said: "Indigenous people and the indigenous world views will definitely need to be brought into the centre of discussion in search of solutions to climate change."

However, a poll this weekend shows dwindling support for environmental issues. A survey by YouGov for the Labour-leaning Left Foot Forward website will make difficult reading for political leaders trying to take voters with them on climate change.

Just 24 per cent believe global warming is an "urgent issue" needing "immediate and radical steps", compared with 38 per cent in a previous YouGov poll in November 2006. And 18 per cent agree that "there is not yet enough clear evidence of global warming and therefore there is no need currently to consider any major steps to change the way we live" – double the 9 per cent in the 2006 poll.

On the agenda

Today

Dr Rowan Williams, the Archbishop of Canterbury, hosts a service in Copenhagen Cathedral where he is expected to make a plea for action. Queen Margrethe II of Denmark is due to attend.

Tomorrow

Final week of negotiations begins. Environment ministers will continue arriving to push negotiators towards an agreement that world leaders will be able to sign later in the week. Douglas Alexander, the International Development secretary, will take part in talks with his counterparts.

Tuesday

The Prince of Wales addresses the summit in an attempt to get support for measures to reduce deforestation. He has no formal role in the negotiations but plans to lobby business leaders privately.

Wednesday

Government ministers arrive as pressure builds over the deadlock between rich and poor countries as to who will pay for going "low carbon", and how to share the burden of cuts on greenhouse gas emissions.

Thursday

Countries will issue a flurry of statements confirming where they stand. Yvo de Boer, head of the UN Framework Convention on Climate Change, hosts a lunch, with a gala dinner hosted by the Queen of Denmark in the evening.

Friday

With Barack Obama in attendance, the pressure is on for an agreement on the final day. If all goes according to plan, a political compromise will be announced, with details to follow. Alas, negotiators could be locked in talks into the weekend.