Is the “climate change” responsible for the 2018 European heatwave? [closed]

Question

The following article Why is Europe going through a heatwave? as well as other articles on the current heatwave in Europe and the British Isles tend to suggest that:

The heatwaves in the northern hemisphere are undoubtedly linked to global warming, scientists say. “There’s no question human influence on climate is playing a huge role in this heatwave,” said Prof Myles Allen, a climate scientist at the University of Oxford.

Is there really scientific support to the “global warming” assumption, or are there enough previous “exceptional heatwave” to suggest that we are still within the range of historical statistical data?

Answer 1

The trouble with this kind of claim is that "the range of historical statistical data" does not provide clear boundaries.

A number of record high temperatures have been set this year. By definition a record is outside of "the range of historical statistical data".

“The first six months of the year have made it the hottest La Niña year to date on record,” said Clare Nullis of the WMO.

Taiwan is the most recent place to report a new high with a temperature of 40.3C in Tianxiang on Monday. This followed a flurry of other anomalies.

Last week, a weather station at Ouargla in Algeria’s Sahara Desert, reported a maximum temperature of 51.3C on 5 July, the highest temperature reliably recorded in Africa.

In Europe specifically this year has not quite set a record overall, but individual records have been set:

In Europe, the WMO has warned of droughts, wildfires and harvest losses after the second hottest June on record. Over the past two weeks, records have been set in Tbilisi (40.5C), Shannon (32C), and Belfast (29.5C)

A better way of thinking about exceptional weather events and climate change is to imagine rolling a loaded dice that comes up six half the time. If you roll it once and it comes up six, is that because it was loaded, or would it have rolled a six that time even if it wasn't loaded? The most you can say for that one event is that the six was probably due to the loading. Now suppose you roll it 100 times and get 47 sixes. That might happen by chance even with an unloaded dice, but it is so fantastically improbable that you can say the result is "no question" due to the loading and ignore the tiny probability that an unloaded dice would have done the same.

In the case of 2018 weather, I would interpret Prof. Allen's statement in the same light. In his expert opinion the extreme weather events around the world at present would be so unlikely without global warming that the possibility can be discounted. If global warming is affecting weather globally, then of course it is also having an effect in Europe because Europe is part of the globe.

So yes, there is scientific support for the proposition that global warming is largely responsible for the exceptionally high temperatures seen around the northern hemisphere this summer, including in Europe.

Answer 2

It's one thing to just chalk off things to "expert opinion" and another to actually look at the study in question, for some quantifiable effect, even if just in probability. I wasn't able to locate this last (Oxford) study yet, but it's far from being the first in this line of research. I found a much older study with ~1000 citations in Google Scholar:

The summer of 2003 was probably the hottest in Europe since at latest AD 1500, and unusually large numbers of heat-related deaths were reported in France, Germany and Italy. It is an ill-posed question whether the 2003 heatwave was caused, in a simple deterministic sense, by a modification of the external influences on climate—for example, increasing concentrations of greenhouse gases in the atmosphere—because almost any such weather event might have occurred by chance in an unmodified climate. However, it is possible to estimate by how much human activities may have increased the risk of the occurrence of such a heatwave. Here we use this conceptual framework to estimate the contribution of human-induced increases in atmospheric concentrations of greenhouse gases and other pollutants to the risk of the occurrence of unusually high mean summer temperatures throughout a large region of continental Europe. Using a threshold for mean summer temperature that was exceeded in 2003, but in no other year since the start of the instrumental record in 1851, we estimate it is very likely (confidence level >90%) that human influence has at least doubled the risk of a heatwave exceeding this threshold magnitude.

And more recent research for the US:

The graph shows the fraction of heat waves for which models projected global warming would be the primary contributor. https://i.sstatic.net/g1MzP.png

(Cannot the include the image presently because of a Stack Exchange error. Click the link for now.)