. Author manuscript; available in PMC: 2016 Jun 6.
Published in final edited form as: Nat Geosci. 2015 Oct 5;8(11):838–842. doi: 10.1038/ngeo2545
Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:http://www.nature.com/authors/editorial_policies/license.html#terms