Global warming fears may be based on a systematic error in climate modelling. According to the article:

The Earth's temperature may have fluctuated more wildly during the past 2000 years than previously thought, according to a new study that challenges how researchers use tree rings and corals to give us a picture of the Earth's past.

If true, the study suggests that recent warming might not be as unique as was thought previously, and might partly be due to natural temperature cycles, rather than humans spewing carbon dioxide into the atmosphere.

More information here.