With the editor's recent announcement of a focus on the environment I can strongly recommend the Guardian's coverage. A lot of their articles get shared here, so here's the source:-

Web: http://www.theguardian.com/environment
RSS Feed: http://www.theguardian.com/environment/rss

Alan Rusbridger's announcement
http://www.theguardian.com/environment/2015/mar/06/climate-change-guardian-threat-to-earth-alan-rusbridger