The earth's climate has changed over the last century and there is new and stronger evidence that most of the warming observed the last 50 years is attributable to human activities.
Moreover, evolving computer models are predicting that temperatures should continue to rise over the 21st century.
This is revealed by the Third Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) which involved many hundreds of scientists from many countries.
more information:
Oceans, Greenhouse Gases Rising Faster - Reports
http://www.planetark.com/dailynewsstory.cfm/newsid/33645/story.htm
Can "Tipping Points" Accelerate Global Warming?
http://www.planetark.com/dailynewsstory.cfm/newsid/33652/story.htm