Evidence for global warming mounts

polar ice contracted to its smallest size in at least a century, according to measurements by space agency NASA and the US National Snow and Ice Data Centre.

Around Harstad, less bone-chilling winters have helped some pests to thrive, like beetles and worms that destroy Arctic forests. In northern Russia, frogs have been spotted more often on the tundra and some birds are not even bothering to migrate.

The idea that humans are to blame is growing: a survey this year by scientists at the US Scripps Institution of Oceanography showing a warming of the Pacific, Atlantic and Indian Oceans over recent decades has been among the strongest evidence that human activities are responsible.