Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.
PERSPECTIVE Correction for “Tipping elements in the Earth System,” by Hans Joachim Schellnhuber, which appeared in issue 49, December 8, 2009, of Proc Natl Acad Sci USA (106:20561–20563; first published December 7, 2009; 10.1073/pnas.0911106106).
Because of a printer error, an incorrect version of this article was published in the print issue; the online version appears correctly.
