"COPENHAGEN -- Tens of thousands of climate activists marched in Copenhagen on Saturday as part of a worldwide 'Day of Action' to urge negotiators at U.N. talks to agree a strong treaty to fight global warming. 'There is no planet B' and 'Change the politics, not the climate', read banners waved by demonstrators in the Danish capital. ... The rally was mostly held in a carnival atmosphere but riot police detained about 400 black-clad activists at the rear after some bottles were thrown and windows smashed. They were forced to sit on a street, hands tied behind their backs." Sunanda Creagh and John Acher report for Reuters Dec. 12, 2009.