On Saturday, more than 25,000 people crowded Trafalgar Square in London to call on world leaders to step up action against climate change, and to push the British government towards year-on-year reductions in greenhouse gas emissions.

Organized by the Stop Climate Chaos - a coalition of environment, trade and community groups - the successful day of action proceeded with no arrests or public disorder while bringing greater attention to global warming in advance of today's United Nations climate change conference in Nairobi, Kenya.