Earth Hour:St. Stephens tower

A combination picture shows the landmark St. Stephens tower of the Houses of Parliament in central London during 'Earth Hour', left, with its lights switched off, and right, following the action, Saturday March 28, 2009. A London Underground sign is seen in both pictures. Time zone by time zone, nearly4,000 cities and towns in 88 countries joined the event sponsored by the World Wildlife Fund to dim nonessential lights from 8:30p.m. to 9:30 p.m. The campaign began in Australia in 2007 and last year grew to 400 cities worldwid.

(AP Photo/Lefteris Pitarakis)