'Very strong' climate change signal in record June heat in the UK and Western Europe

Matt McGrath BBC News 30 Jun 17;

The June heat waves that impacted much of the UK and Western Europe were made more intense because of climate change say scientists.

Forest fires in Portugal claimed scores of lives while emergency heat plans were triggered in France, Switzerland and the Netherlands.

Britain experienced its warmest June day since the famous heat wave of 1976.

Human-related warming made record heat 10 times more likely in parts of Europe the researchers say.

During June, mean monthly temperatures about 3C above normal were recorded across western parts of the continent. France experienced its hottest June night ever on 21st when the average around the country was 26.4C.

That same day had seen the mercury hit 34.5 at Heathrow in what was the UK's warmest June day for 40 years.

It was a similar story in the Netherlands which is set to have its hottest June on record while in Switzerland it was the second warmest since 1864.

Now, researchers with World Weather Attribution have carried out a multi-method analysis to assess the role of warming connected to human activities in these record temperatures.

"We simulate what is the possible weather under the current climate and then we simulate what is the possible weather without anthropogenic climate change, and then we compare these two likelihoods which gives us the risk ratio," Dr Friederike Otto from the University of Oxford, one of the study's authors, told BBC News.

"We found a very strong signal."

That signal, according to the authors, made heat waves at least 10 times more likely in Spain and Portugal.

Fires resulted in the deaths of 64 people in Portugal, while in Spain they forced the removal of around 1,500 people from holiday accommodation and homes.

In Central England, France, Switzerland and the Netherlands the intensity and frequency of such extreme heat was four times as likely because of climate change, the study says.

"We found clear and strong links between this month's record warmth and human-caused climate change," said Geert Jan van Oldenborgh, senior researcher at the Royal Netherlands Meteorological Institute (KNMI).

"Local temperature records show a clear warming trend, even faster than in climate models that simulate the effects of burning fossil fuels but also solar variability and land use changes," van Oldenborgh added.

The researchers say their reported results on the impact made by human related warming are conservative in some ways. Their study indicated that in countries like Spain, Portugal and France, climate change could be increasing the chances of extreme heat by up to forty times.

The scientists believe that the chances of these extreme heat events becoming much more common will increase unless rapid steps are taken to reduce carbon emissions.

"Hot months are no longer rare in our current climate. Today we can expect the kind of extreme heat that we saw in June roughly every 10 to 30 years, depending on the country," said Robert Vautard, a researcher at the Laboratory of Climate and Environmental Sciences (LSCE), who was also involved in the study.

"By the middle of the century, this kind of extreme heat in June will become the norm in Western Europe unless we take immediate steps to reduce greenhouse gas emissions."

The researchers are calling on city leaders in particular to work with scientists and public health experts to develop heat action plans.

While, usually, researchers wait to publish research like this in a peer-reviewed journal, the team felt that speed was necessary to inform public debate.

"When extreme events happen, the question is always asked 'what's the role of climate change?' and often the statement is made by a politician or by someone with a political agenda and not based on scientific evidence," said Dr Otto.

"Our aim is to provide that for the role of climate change, to show what you can robustly say within the time frame when people are discussing the event."