Environmental Leader: While one study shows that climate change risks could cost nations nearly 20 percent of their GDP by 2030, another one indicates that some countries including Mexico and Argentina are leading the way to a low-carbon economy. Climate change risks could cost nations up to 19 percent of their GDP by 2030, with developing countries most vulnerable, according to a new report from the Economics of Climate Adaptation Working Group. The report also finds that cost-effective adaptation …