News.com.au: NICHOLAS Stern, one of the world’s leading environmental economists, said today that the global economy will face a more severe downturn than the current crisis if it fails to halt climate change. Lord Stern, the author of a key climate change report and a former World Bank chief economist, said moves towards a low carbon economy should not be stifled by the fallout from the current economic downturn. “One thing we should have learned from this experience of the financial …