Millions unplug for Earth Hour

Now in its fourth year, Earth Hour promises to be the biggest ever, organisers said, with thousands of cities and towns in 125 countries - 37 more than last year - pledging to take part following last year's failed climate talks.

This photo shows the landmark India Gate, with lights switched on (top) and the lights turned off (below), as part of Earth Hour in New Delhi on March 27, 2010. (AFP Photo)

This picture shows a view of Malaysia's landmark Patronas Twin Towers is seen before (L) and during lights out (R) for Earth Hour in Kuala Lumpur. (AFP Photo)

This grid of three photos shows the Brandenburg gate in Berlin while its lights are gradually being turned off as part of Earth Hour. More than 120 countries participate in turning off lights for 60 minutes from 8:30 to 9:30 in the evening local time in an effort to raise global awareness on climate change. (AFP Photo)

This combination photo shows the ancient Parthenon Temple on top of the Acropolis hill before and during lights out as Greece participates in Earth Hour in Athens. (AFP Photo)

From a shopping mall in Manila to the Eiffel Tower in Paris and the Empire State Building in New York, landmarks and skylines will dim. (AFP Photo)

This split image shows the Empire State Building (L) in New York, Big Ben (C) in London and the Eiffel Tower (R) in Paris with lights turned off during Earth Hour on March 28, 2009. Icons including the Great Pyramids, Eiffel Tower and China's Forbidden City will be plunged into darkness as millions take part in the rolling grassroots movement aimed at thwarting climate change. (AFP Photo)

This image shows Sydney Harbour Bridge, with lights on (top) and lights off (below) as part of Earth Hour. (AFP Photo)