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Been there before, and survived beautifully February 13, 2010

Posted by BlueGreen in Deception, Doesnt Understand, Misrepresentation.
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Bolt’s Post 13 February, 2010

Bolt asks a question:

So if the science on the MWP [Medieval Warm Period] is not settled, why did the IPCC use the since-discredited ”hockey stick” of IPCC author Michael Mann to claim it was?

But does he really want to know the answer?

Well, if he does, SkepticalScience can provide it:

Since the hockey stick paper in 1998, there have been a number of proxy studies analysing a variety of different sources including corals, stalagmites, tree rings, boreholes and ice cores. They all confirm the original hockey stick conclusion: the 20th century is the warmest in the last 1000 years and that warming was most dramatic after 1920.

I wonder, does Bolt understand what the grey shade is above and below the temperature line? They are uncertainties. Note that the uncertainties are a measure of the possible variation expected from the “true” or “real” temperatures. What this means is that, whilst the data collected provides the plotted temperature series (black line with 40 year running average in blue), theoretically, the temperatures at each point of the series could actually lie anywhere in the grey shaded area. And this is what sceptics use to suggest that the global temperature could have been as high as it is today by virtue of the uncertainties.

However, those sceptics that say it actually was as high are being disingenuous and misleading. The time series itself and its relatively continuous nature from one point to the next, in relation to the uncertainty, suggest that a “reasonable degree of confidence” can be assumed in the legitimacy of the temperature series.

However, as SkepticalScience says:

The principal result from the hockey stick is that global temperatures over the last few decades are the warmest in the last 1000 years.

No one denies that there were errors made in the initial study produced by Mann. But to continue to assert that the whole area of long term temperature estimation using ice core data and other temperature proxies is discredited and that subsequent results from reanalysis are unusable is untrue and deceptive.

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