IPA claims global warming is natural

This is an advocacy story but it highlights why I prefer modern metrics, not proxy reconstructions.

Source: Why the IPA's claim global warming is natural is 'junk science' | Graham Readfearn | Environment | The Guardian

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So when two staffers at Australia’s Institute of Public Affairs managed to get some “science” into a journal earlier this month, there was much delight in conservative media outlets, together with a distinct lack of any genuine scepticism.
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First, the pair used what’s known as proxy temperature records. These are estimates of past temperatures going back as far as 50AD that have been estimated from analysis of things such as tree rings and lake sediments.

There are hundreds of these temperature records but the authors chose only six, and they don’t say why they chose the ones they did.

They then fed these temperature records into several pieces of software and finally into another piece of software that performs a “machine learning” process. Out the other end comes a series of temperature reconstructions, from which Abbot and Marohasy make two claims.

First, they claim that their resulting data shows the world would have warmed by almost as much as it already has, even if the industrial revolution had not happened and we had not added any extra greenhouse gases to the atmosphere.

Second, they claim that if you were to double the amount of CO2 in the atmosphere then you would eventually see planet-wide warming of just 0.6C. Their estimate of this “equilibrium climate sensitivity” (ECS) is much lower than other studies (the UN’s Intergovernmental Panel on Climate Change says, for example, that studies show the likely range will be between 1.5C and 4C).
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Since the 1850s, modern instruments have built up a traceable record of temperatures with precise times and dates which proxy records are at best, coarse approximations. Berkley Earth has done an excellent job of culling the credible records from these sources to up current dates and times.

Understand I like ice cores but they are limited in geography and some variability in time and date.

Bob Wilson