Europe’s heat wave

Why is it so effing hot? Europe’s heat wave explained

Temperatures are soaring above 40C across Europe.

BY VICTOR JACK AND KARL MATHIESEN

Europe is in the grips of a fierce heat wave, with temperatures this week set to break new records — possibly leading to thousands of excess deaths.

The heat expected to hit Western Europe on Monday and Tuesday follows days of intense weather on the Iberian Peninsula, where hundreds have already died as a result of blistering heat that experts say was made worse by climate change.

The U.K. Met Office issued its first-ever Red Warning for extreme heat in England — indicating a “danger to life” — with temperatures possibly rising to 43C on Tuesday.

Meanwhile, in France, temperatures are also pushing beyond 40C and in the southwest of the country, thousands of people have been evacuated after wildfires burned through more than 10,000 hectares.

Parts of Germany may also reach 40C by the middle of the week, while Eastern European countries will suffer the most on Thursday.

If there's one thing politicians want to avoid, it's a repeat of 2003, when a heatwave in Europe killed more than 70,000. So far, more than 1,000 people have died from heat-related effects in Spain and Portugal.

Here's what you need to know about Europe's latest heat wave.

How can extreme heat be deadly?

The most immediate risks are heatstroke and heat exhaustion, which in some cases can be fatal — particularly among older adults and people exercising or working in high temperatures.

As the temperature rises, sweating increases to cool the body down by evaporation. Also blood vessels near the skin dilate allowing blood to move out from the body's core to its extremities. Without rehydration this can put extra strain on the heart and mean blood pressure falls dangerously low — leading to organ failure in extreme cases.

Also, when the ambient temperature exceeds the body's 37.5C, sweating itself becomes less effective. "Sweat is evaporated by heat from the air, not by the body. Therefore sweating is not as efficient at cooling you down," said Dr Simon Cork, a senior lecturer in physiology at Anglia Ruskin University,

Heatstroke occurs when the body can no longer maintain its temperature and can lead to brain and organ damage without rapid emergency treatment.

But a heat wave's real death toll tends to be much higher than reported. Because heat places the body's cells and organs under stress, it tends to exacerbate existing conditions and vulnerabilities. Particularly among the sick, older people and the very young, the strain of dealing with high temperatures can take a serious toll several days, or even weeks, later.

"Heat waves do really kill a surprising number of people,” said Hannah Cloke, natural hazards researcher at the University of Reading.

Temperatures as low as 25 degrees can worsen cardiovascular problems, the leading cause of heat-related death among over-65s, said Mike Tipton, professor of human and applied physiology at the University of Portsmouth.

High temperatures also reduce air circulation and lead to an uptick in air pollution, worsening respiratory issues like asthma with potentially fatal consequences.

40C is normal elsewhere in the world — why are we worried?

In many European countries, buildings are not designed to withstand temperatures even 5 degrees above 20C, according to Mariam Zachariah, climate scientist at Imperial College London.

That's a serious issue in northern Europe, where most houses are built to trap heat in order to help residents better withstand the cold, causing indoor temperatures to soar during a heat wave. Only a tiny fraction of these homes have air conditioning.

Cities that weren't built to withstand high temperatures also in many cases don't have the right infrastructure to keep people cool — think lots of shade and access to green spaces and water — or emergency response measures to help the most vulnerable.

Is this climate change?

Yes. The build up of CO2 from burning fossil fuels has made heat waves more intense and more frequent across the globe, including in Europe.

"The chances of seeing 40C days in the U.K. could be as much as 10 times more likely in the current climate than under a natural climate unaffected by human influence," said Nikos Christidis, a climate attribution scientist at the U.K. Met Office.

Climate change drives heat waves in two ways, Zachariah said. One is simply by trapping more heat in the global system. “A warmer atmosphere means more heat extremes,” she said.

The second impact is “dynamic” — meaning changing weather patterns, which can bring heat and rain to regions that don’t normally experience them. In Europe's case, this year a slow-moving high-pressure area has brought scorching air up from North Africa.

These kinds of heat waves will become more frequent in the decades ahead, even if governments follow through on their pledges to cut emissions — which is far from a given.

"Even with current pledges on emissions reductions, such extremes could be taking place every 15 years in the climate of 2100,” said Christidis.

How should policymakers respond?

In France, city councils have made museums and other air conditioned places free of charge, and extended pool opening hours. Municipal authorities also have registers for the vulnerable and check in with those who live alone and may be at risk.

London this week set up free water points and announced emergency provisions for rough sleepers.

But beyond the immediate measures, countries need long-term heat action plans, said Sjoukje Philip from the Royal Netherlands Meteorological Institute. That means planting more trees in cities, building heat resistant homes, retrofitting buildings and establishing robust early warning systems.

The EU is urging city and government officials to take these measures. "Climate change adaptation is fundamental and needs to become faster, smarter and more systemic," a spokesperson for the European Commission told POLITICO.

Is Europe a special case?

Although heat waves affect most parts of the world, there are regional differences, according to Philip.

“Heat waves in Western Europe heat up faster than in some other regions,” he said. “Various factors can influence this: drying out of the soil, changes in the jet stream, [or] high-pressure areas that often remain in one place for a long time.”

Research by the Intergovernmental Panel on Climate Change shows that temperatures are set rise across Europe at a rate exceeding average global temperature changes in the years to come, while the frequency and intensity of hot extremes will increase too.