Cherry picking, with a confidence level greater than 99%

We get to hear that there is a consensus. That 97% of the (climate) scientists believe humans cause global warming or something of the like. But this article Is global warming just a giant natural fluctuation? took it a step further. The claim is that the natural-warming hypothesis may be ruled out with confidence levels greater than 99% and, why stop there, most likely greater than 99.9%.

The article is about the recently published paper Scaling fluctuation analysis and statistical hypothesis testing of anthropogenic warming of Shaun Lovejoy (McGill University) in Climate Dynamics.

An analysis of temperature data since 1500 all but rules out the possibility that global warming in the industrial era is just a natural fluctuation in the earth’s climate, according to a new study by McGill University physics professor Shaun Lovejoy.

Interesting. He didn’t want to rely on climate models and took a statistical approach with historical data:

The study, published online April 6 in the journal Climate Dynamics, represents a new approach to the question of whether global warming in the industrial era has been caused largely by man-made emissions from the burning of fossil fuels. Rather than using complex computer models to estimate the effects of greenhouse-gas emissions, Lovejoy examines historical data to assess the competing hypothesis: that warming over the past century is due to natural long-term variations in temperature.

This is the part where the rabbit came out of the hat:

“We’ve had a fluctuation in average temperature that’s just huge since 1880 – on the order of about 0.9 degrees Celsius,” Lovejoy says. “This study shows that the odds of that being caused by natural fluctuations are less than one in a hundred and are likely to be less than one in a thousand.

Let’s summarize what we have until now: going back until 1500 (with proxy data), he finds a huge fluctuation of the average temperature since 1880 (with temperature data from the instrumental record). Man is industrializing since that time, so man is responsible for this increase in temperature.

For those who didn’t noticed it yet, I repeat:

Going back until 1500, he finds a huge fluctuation of the average temperature since 1880.

He couldn’t cherry pick his start dates more than that! A period called “The Medieval Warm Period” came to an end at the beginning of the 1400s and a cold period called “The Little Ice Age” started. This cold period ended around 1850.

Notice anything?

The period that represents the natural influences stretches over a cold period and the recovery from this cold period is used as the period that represents human influences. No wonder they find human influence on climate with a confidence level of 99.9%.


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