Thursday, July 2, 2009

Copenhagen Synthesis Report Climate Change

I started reading this report because the Real Climate (RC) blog responded to another scientist's (Roger Pielke Sr.) criticism of RC's commentary on the report. I have always liked what Pielke wrote, so I went over to Climate Audit (CA) to see what they were saying. They were trying to replicate the results in the first figure presented in the report. This attempt was thwarted by the original authors by not specifying algorithms and parameters that would allow a replication. And...CA's closest approximation to the figure was using parameters which they found suspect.

The situation is worsened by the fact that the figure in the report supports the warnings in the report. CA's creation of a similar plot (i.e. using the same data and filtering techniques) arrived at a different result which showed less dire consequences. What does this mean? Is it sloppiness? Was an embarrassing bug found in the algorithm? Was it data manipulation? How does one choose a particular technique based on desired outcome? How robust are these techniques if they can give such different results when operating on the same data?

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