Encyclopedia of the earth (http://www.eoearth.org/):
http://www.eoearth.org/article/Climate_Change_(collection)

"The last two decades of the 20th century produced mounting evidence that
climate change posed significant risks to society. At the beginning of the
21st century, climate change has become a defining issue of our time. The
importance of this issue is underscored by its magnitude and complexity: it
is a global problem with wide geographic and economic disparity between the
largest sources of the problem and those who will experience the greatest
impacts. Many solutions often run counter to powerful entrenched interests
and long-held patterns of individual behavior. All of this is happening
amidst a global community that is increasingly connected by flows of
information, people, commerce and environmental change. This collection
brings together some of the world's leading scientists and organizations and
presents the essential knowledge underlying the issue of climate change." -
Cutler J. Cleveland, Editor-in-Chief.