A three-day conference on "Holistic response to climate change' began at the SM Convention Centre here today. The conference is being organised by the World Environment Foundation. Around 300 experts will discuss the issue of climate change during the three-day conference. Dr Madhev Mehra, president of World Council For Corporate Government, UK, said climate change could reduce global consumption of various products by 20 per cent. That could mean GDP reduction of 5 per cent.