Sunday, February 14, 2010

Medieval Warm Period

Dr. Phil Jones, former director of CRU (Climatic Research Unit) at UAE (University of East Anglia), granted an interview of sorts to the BBC. They sent him questions, and he answered them, including links to graphs. You will find the complete exchange here. Dr. Jones is at the center of the Climategate affair. His answers to the BBC seem sincere and thorough to me. The last few months must have been hard on Dr. Jones. I'm glad to see him talking to the press. The BBC's questions were pointed. There is no sign of the global warming zealotry that I had come to expect from the BBC. I'm sure Climategate has been hard on the global warming zealots as well. But the BBC appears to be responding by putting their journalistic principles first.

Of particular importance to the debate over the Hockey Stick graph and its associated Mann-Made Warming, is the existence or non-existence of the Medieval Warm Period (MWP). The BBC asked Dr. Jones if the MWP was warmer than today, and here's his answer.

"There is much debate over whether the Medieval Warm Period was global in extent or not. The MWP is most clearly expressed in parts of North America, the North Atlantic and Europe and parts of Asia. For it to be global in extent the MWP would need to be seen clearly in more records from the tropical regions and the Southern Hemisphere. There are very few palaeoclimatic records for these latter two regions."

Indeed: there is plenty of evidence in the Northern Hemisphere that the MWP was 2°C warmer than today. Even the IPPC said as much back in 1995, before the Hockey Stick graph was published. Whether or not we need evidence from the Southern Hemisphere to believe in the MWP is a matter of opinion. If it were possible for the Northern Hemisphere to warm 2°C while leaving the Southern Hemisphere unchanged, this would suggest that a 2°C warming can be both natural and local. If the MWP were global, we see that a 2°C warming can be natural. Either way, the Northern Hemisphere's MWP is evidence that 2°C warming from current temperatures can occur naturally.

Dr. Jones's full answer shows that he understands the implications of the MWP. In another answer, he says there has been no statistically significant warming since 1995, but he adds that, "This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level." Reports of Dr. Jones performing a U-Turn appear to be over-blown. But at least he is talking.

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