By: Miaomiao Yu

People are sitting in their houses, afraid of the intense heat outside, and events are being canceled due to the extreme temperature. This year’s summer has been surprisingly hot, and there are still two more months to go.

Heat waves in Europe are increasing in temperature and frequency at a faster rate than almost any other part of the planet. France experienced record high temperatures in some cities both two months ago and last month. Other countries such as Spain and Italy also experienced the heat last month along with France. This month, Poland and other parts of Eastern Europe suffered from another wave of heat.

Temperatures across Europe are soaring high, at or near three digits, from Spain to the British Isles and spreading east. Wildfires are breaking out and the majority of the continent is in a drought. Many citizens are wondering what is causing this extreme weather.

Global warming plays a role. Average temperatures around the world are 2 degrees Fahrenheit higher than they were in the late 19th century, before carbon dioxide emissions and other heat-trapping gasses became widespread.

Other factors such as the circulation of the atmosphere and the ocean also make Europe a heat wave hot spot. For example, disturbances in the air can draw heat to Europe, and ocean stream fluctuations can also affect temperature in regions.

The current temperatures in England and Wales are caused by a region of upper level low-pressure air that has been stalled off the coast of Portugal for days. This is known as a “cutoff low” because it was cut off from westerly winds, the mid-latitude jet stream, that circles the planet at high altitudes. Low-pressure zones tend to draw air toward them, and in this case, the low pressure zone draws hot air from Africa into Europe.

Scientists linked the change in the jet stream to part of the increase in temperature in Europe. Many European heat waves occurred when the jet stream had temporarily split into two, leaving an area of weak winds and high-pressure air between the two branches. This area leads to the buildup of extreme heat.

There may be more reasons for Europe’s heat waves, although some of them are being debated among scientists. Natural climate variability can make finding specific influences difficult, Efi Rousi, a senior scientist at Potsdam Institute for Climate Research in Germany, said.

Warming in the Arctic may also play a role. As the Arctic warms at a faster rate, the temperature difference between it and the equator decreases. This leads to a decrease in summertime winds, which makes weather less variable.

There are also indications that changes in the Atlantic Meridional Overturning Circulation affect Europe’s climate. A study using computer simulations has shown that a weakening of the current would cause changes in atmospheric circulation, leading to drier summers in Europe.

An area that has already experienced a heat wave is more prone for others to occur in the same area because the extreme heat dries the soil. When there is moisture in the soil, some of the sun’s energy is used in evaporating the water, slightly cooling the temperature. However, when there is no more moisture left in the soil to evaporate, the sun bakes the surface, adding to the heat.