שינויים

* העלמות יערות הצפון{{הערה|Timothy M. Lenton, Hermann Held, Elmar Kriegler, Jim W. Hall  , Wolfgang Lucht  Stefan Rahmstorf, and Hans Joachim Schellnhuber [http://www.pnas.org/content/105/6/1786.fullTipping elements in the Earth's climate system] 21.11.2007 Proceedings of the National Academy of Sciences of the United States of America}}{{הערה|סוכנות החלל האמריקאית [https://climate.nasa.gov/nasa_science/science/ The study of Earth as an integrated system]}}

* העלמות יערות הצפון{{הערה|Timothy M. Lenton, Hermann Held, Elmar Kriegler, Jim W. Hall  , Wolfgang Lucht  Stefan Rahmstorf, and Hans Joachim Schellnhuber [http://www.pnas.org/content/105/6/1786.fullTipping elements in the Earth's climate system] 21.11.2007 Proceedings of the National Academy of Sciences of the United States of America}}{{הערה|סוכנות החלל האמריקאית [https://climate.nasa.gov/nasa_science/science/ The study of Earth as an integrated system]}}