Posted by Curt on 1 October, 2016 at 5:00 pm. 1 comment.


Dr. Sebastian Lüning and Prof. Fritz Vahrenholt:

It was some three years ago when Potsdam climate scientist Srtefan Rahmstorf railed against the German DWD National Weather Service at his Klimalounge site. The DWD indeed had dared to contradict Rahmstorf. The issue was about the relationship between Arctic sea ice extent and cold winter weather in Europe. Rahmstorf’s simple model: less Arctic sea ice [from global warming] causes cold European winters.

To back this up, he listed studies and claimed:

In my view, the above studies provide strong evidence for a link between Arctic ice loss due to global warming, more frequent winter high pressure, especially over the Atlantic-European part of the Arctic, and an associated influx of cold air to Europe. As we have often seen in recent winters – for example in a spectacular way in the first half of February 2012.”

Here Rahmstorf made wild assertions and dished out loads of harsh criticism, calling the DWD “embarrassing”, and incompetent with questions concerning climate change, and claiming that it couldn’t even read scientific publications, and that it had made a trivial argument”. That’s an unusually aggressive manner of discussion one seldom sees in science. Rahmstorf tone:

However, the taz quoted [German paper] yesterday the spokesman of the German Weather Service [DWD in German] as saying that if there was a direct relationship with the sea ice cover,  the entire winter would have to be very cold in Germany. I think this trivial argument with which he would like to wipe from the table the climate research results shown above is pretty embarrassing for the DWD.  Of course open water in the Arctic  does not prevent stochastic weather variability.  There will always be warm and cold periods. In all these studies it comes down to changing probabilities in the prevailing weather patterns: Petoukhov and Semenov estimate that the probability of cold winter extremes could triple, that is even in the Abstract. One wonders whether the DWD representative has read the relevant studies at all – and if not, why he feels the urge to comment on them in the media. Unfortunately, it has a certain tradition that meteorologists dealing with weather, are not familiar with climate science.”

It’s now been three years since Rahmstorf’s outburst. In the meantime research has since looked at the subject professionally and is now able to present the first robust results. On 11 August 2016 a group of scientists led by Hans Chen of Pennsylvania State University presented a paper in the Journal of Climate that will cause some sleepless nights for Stefan Rahmstorf.

Rahmstorf was not even close

The bitter findings: Rahmstorf was not even in the ballpark. He unjustifiably mistreated the DWD. The truth is, according to Chen et al. 2016, there is no robust relationship between Arctic sea ice and the weather at the middle latitudes.

Here are some excerpts of the study:

These results show that the linear relationship between Arctic  sea-ice loss and mid-latitude weather patterns is weak, suggesting that the remote atmospheric  response is small compared with the internal variability, or highly nonlinear with respect to the  sea-ice area anomalies.”


Thus, our results do not show evidence of an unusually elongated jet stream associated with  Arctic sea-ice loss on a monthly time scale.”


We have shown using several different metrics that the remote atmospheric response can be non-robust due to internal dynamics alone,  and leave diagnosis of mechanisms behind this non-robustness for future studies.”

In anutshell: Cold weathers are weather.

Rahmstorf’s attempt to “anthropogenize” winter weather failed big-time.

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