Read just a little bit harder. The paper cites those sources:
Quote:
...prompts some popular commentators
(2, 3) to doubt the existing understanding of the relationship
among radiative forcing, internal variability, and global surface
temperature.
|
Footnote 2 is the
Center for Research on Globalization and 3 is the Australian newspaper.
They weren't scientific cites, otherwise the paper would not appear in the Publication of the National Academy of Sciences. The authors go on to disagree with these commentators.