Europe Mobilizes as ‘On-the-Fly’ Attribution Study Tags Climate Change for Record Heat Wave

With the south of France feeling like Death Valley this past weekend, and much of Italy on “red alert,” attribution science experts have declared that climate change made the current heat wave “at least five times more likely, and 4.0ºC hotter” than would have been the case without global warming.

“Across Europe in June, from the Czech Republic to Switzerland to Spain, new heat records tested the Continent’s defences,” reports the New York Times, as soldiers fought wildfires, schools became shelters, and social workers “raced to the homes of older people to prevent mass deaths,” especially in places where night-time temperatures remained dangerously high.

This past Friday, the mercury rose higher than had ever been recorded in France, with the southern town of Gallargues-le-Montueux reporting a roasting 45.9ºC.

“It is part of an unmistakable trend,” observes the Times, noting that “the hottest summers in Europe in the last 500 years have all come in the last 17 years.”

While declaring it “premature” to attribute the current scorcher to climate change, a statement by the World Meteorological Organization acknowledged it as “consistent with climate scenarios which predict more frequent, drawn out, and intense heat events as greenhouse gas concentrations lead to a rise in global temperatures.”

Such is certainly the case in France, writes the Times, with national weather service Météo-France reporting a doubling in the number of heat waves since 1985 and forecasting another doubling by 2050, accompanied by an increase in intensity.

Describing  the heat wave as “a war, a battle on two fronts, on the front of causes and effects,” Environment Minister François de Rugy urged those watching his televised address to “understand that these exceptional situations risk becoming more frequent.”

Just how much more frequent is the question that attribution science seeks to explain, writes the Times, noting that “extreme weather events have always happened, and heat waves would occur even without global warming.” What the computer modelling of attribution science increasingly shows, however, is just “how much global warming has stacked the deck in favour of any given weather event.”

According to the scientists at World Weather Attribution, for example, the aptly-named Lucifer heat wave which scorched the Mediterranean in 2017 “was made at least 10 times more likely by climate change,” while the devastating heat of 2010 which left Siberia in flames was made 80% more likely.

While multiple factors determine such retrospective probabilities, including the location and season of a particular extreme weather event, attribution scientists are growing ever more interested in the role of a “meandering” polar jet stream which is weakening as the Arctic warms, undermining the temperature differential on which a strong jet stream depends. Without a steady jet stream to push them along, weather systems tend to stick around.

Veteran climate hawk and Penn State University atmospheric scientist Michael Mann told CBS that what he calls “planetary wave resonance” has indeed produced a kind of storm system “traffic jam” off the west coast of Portugal which is, in turn, forcing a persistent flow of hot air from North Africa into Europe.

Mann also confirmed the link between a scorching Europe and a frighteningly warm Arctic: “Extreme warmth in the Arctic and the loss of Arctic sea ice due to human-caused climate change favours this jet stream pattern,” he said, “and indeed we are right now witnessing record Arctic warmth and record-low sea ice for so early in the season.”

Back in France, and “in the heart of the heat wave,” writes the Times, a World Weather Attribution team has just completed an “on-the-fly” attribution study which declared the current heat wave to have been made five times more likely by climate change.

Royal Netherlands Meteorological Institute climate expert Geert Jan van Oldenborgh told the BBC that “heat waves are becoming more common in Europe for sure. We’d better get used to it, because they will get worse in the future.”

Meantime, says the Times, “2019 is on track to be among the hottest years on record, and Europe is on the front line.” So far, the line is holding: unlike some other parts of the world, “its wealth and social safety net have kept it from being ravaged. Hospitals work. Paramedics respond. Farmers have crop insurance.”