The 10th anniversary of Earth Hour takes place on Saturday 25 March between 8.30pm and 9.30pm, and over half a million people in Wales will take part in the annual event that sees millions worldwide switch off their lights to shine a light on climate change. Iconic landmarks taking part include Caernarfon Castle, National Library of Wales in Aberystwyth, National Waterfront Museum in Swansea, and the Senedd and Principality Stadium in Cardiff. To mark the occasion, WWF Cymru is to…