Scientists from Harvard have released a report that temperatures in the middle ages were much warmer than present day temps.
These findings raise concerns that the data used to push global warming covers too short of a time span to be useful. The rises in temps could just be a recovery from the mini-ice age. It also calls into question what is “normal climate”.
It is not a blow in the least to global warming theory. Why would it?
There is little doubt among climatologists that human activity is contributing to global warming. CO[sub]2[/sub] is a greenhouse gas and there is no doubt that the levels have increased in the last 100 years. What is in debate is how much this increase in CO[sub]2[/sub] is affecting the global average temperature and whether or not the natural carbon cycle can deal with it.
Indeed, not to mention the increase in airborne dust generated by industrial activities is suspected to be artifically pushing temperatures downward.
The Secret Life of Dust - a fascinating book.