Boers, N.
Bookhagen, B.
Barbosa, H. M. J.
Marwan, N.
Kurths, J.
Marengo, J. A.
Article History
Received: 20 June 2014
Accepted: 9 September 2014
First Online: 14 October 2014
Competing interests
: The authors declare no competing financial interests.