The seasons are natural climate variations, a word derived from the Latin satin, act of sowing, from satus, past participle of serere, to plant. Seasonings enhance the flavor of food, add zest to speeches, make us competent through trials and troops seasoned by battle. The variability of our environment keeps life interesting.

Eagerly awaited is the release on Thursday, June 22 of the report of the National Academy of Sciences on ‘
Surface Temperature Reconstructions for the Last 2,000 Years‘, describing and assessing the state of scientific efforts to reconstruct surface temperature records for the Earth over approximately the last 2,000 years based on tree rings, boreholes, ice cores, and other “proxy” evidence.

The earth has seasons on an annual timescale. There are seasons on a 100,000 year timescale, where glaciations are punctuated by warmer periods, such as the present. The release on Thursday, June 22 of the report of the National Academy of Sciences addresses the controversial question: “How seasonal is climate over the Millennial timescale”, a period called the late Holocene.

To recap on the controversy, the congressionally requested report was to mediate between opposing ‘teams’. One team, proponents of the ‘hockey stick graph’ index of past climate, captained by Michael Mann, and featured in the IPCC 2001, maintain that average global temperatures have been relatively stable until the last century when the emission of greenhouse gasses (GHGs) suddenly pushed up temperatures. They believe in a Holocene without seasons.

On another team are paleoclimatologists such as Esper and Moberg who suggest the index has much greater variation over the past 2000 years — the ‘broken handle’. They also think the climate 1000 years ago, a period known as the Medieval Warm Period (MWP) was almost but not quite as warm as today. So all other things being equal, GHGs have produced some warming.

A third team lead by McIntyre maintains the indices of both those teams are flawed, tending to artificially mine data for hockey stick graphs — the ‘broken blade’. He thinks it is possible, as evidenced by robust indices such as tree-lines, that climate during the MWP was warmer than today. All other things equal, suggesting little or no warming due to GHGs.

He also claims the other teams are ‘hiding the ball’ by not submitting data to public archives, failing to reveal results of model validations that would be detrimental to their case, and carry out basic due diligence. He has shown that much existing ‘evidence’ for global warming has errors and cannot at this point be exactly replicated.

While it will probably be expecting too much to expect a resolution from the report on Thursday, It will be interesting to see if they think that ‘unfair play’ has entered into the game. Clearly there is a clash of cultures and expectations of research. The congressional clients come from a background in law and economics with clear ideas of what constitutes evidence, replication, truth, and written professional codes of conduct. The scientific researchers come from a different world where mathematical models are on a par with measurements, agreement with the big picture constitutes replication, global warming is incontestable, and codes of scientific conduct are based largely in tradition.

I expect there may triumphalism all round for the cheerleaders of the teams in the ‘great hockey stick graph debate’. But in science, everyone can’t be winners. Theories must be falsified for science to progress.

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