The world has just gotten its first real taste of a planet that is 1.5 degrees Celsius — or 2.7 degrees Fahrenheit — hotter than preindustrial times.
Following the hottest June on record and a series of extreme weather events—including heatwaves in Europe, North America, and Asia, plus wildfires in Canada and Greece—data from the Copernicus Climate Change Service (C3S) show that the July temperatures were a whopping 5 standard deviations above the 1971-2000 average. That is not random variability.
According to data from the C3S, July of this year was the most scorching July on record, clocking in at somewhere between 1.5 and 1.6 Celsius hotter than the average before the widespread use of fossil fuels.
C3S is implemented on behalf of the European Union by the European Centre for Medium-Range Weather Forecasts (ECMWF), an independent intergovernmental organization supported by 35 states.
Europe experienced a weather pattern with some of the hottest temperatures as a ‘heat dome’ over the southern half of the continent allowed a warm air mass to build up under a high-pressure system, creating stable and dry conditions.
The Northern Hemisphere was deeply affected by widespread record-breaking fires in Canada since the beginning of May, as large fires also raged across eastern Russia fueled in part by extreme heat waves and record droughts that scientists are blaming on global warming.
“The current extreme heat is due mainly to a slow-moving anticyclone, a high-pressure system, that is dominating the upper atmosphere over southern Europe,” explained Florian Pappenberger, Director of Forecasts at ECMWF. “Anticyclones cause subsidence or downward motion of air. As the air mass moves down it is compressed and thus warmed.”
Such high-pressure systems are also associated with reduced cloud cover, allowing more solar radiation to reach the ground. This in turn allows for substantial heating of Earth’s surface by the sun, heat which then moves upwards into the atmosphere. The long days and short nights of summer mean that this heating effect is maximized.
Advection, that is broadscale winds blowing in this case hot air from one place to another, for example from northern Africa into Europe, can also contribute to heatwaves. For the current heatwave that seems to be less important, but in other cases it can be the main factor.
Another possible influence on Europe’s current weather is the Atlantic Ocean heatwave that was reported on in early July. During June, and into the start of July, the Atlantic Ocean has been warmer than average across most of its basins, especially near North America and Europe.
While atmospheric circulation can affect the ocean, the opposite is also true. For example, ocean heat waves can affect atmospheric circulation patterns and can also warm up the air masses above them.
Sea surface temperature anomalies in the eastern North Atlantic have reduced since the exceptional peak in June, but marine heatwaves continue in parts of the region.
Heat stress is the impact the environment has on the human body, accounting for temperature, humidity, wind speed, and other factors.
Data for summer 2023 up until 15 July show that large parts of southern Europe have already seen up to 10 days of ‘very strong heat stress’, and parts of southern Spain have experienced up to 30 days of ‘very strong heat stress’.
Last year, southern Spain saw 50-60 days of very strong heat stress, and in some small areas, up to 70 days, over the whole summer.
Gigantic wildfires also burned across Siberia on a record scale that is larger than all the fires raging this summer around the world combined.
This region has already seen some days with ‘extreme heat stress’ so far this summer, and it is likely that the data will show that parts of southern Europe experienced ‘extreme heat stress’ during the most recent heatwave.
“In the longer term, as the climate warms, Europe is seeing an increasing number of summer days with ‘very strong heat stress’, and in southern Europe, an increasing number of days with ‘extreme heat stress’. A recent study in Nature Medicine indicated that more than 60,000 people in Europe lost their lives due to the extreme heatwaves last summer,” explained Carlo Buontempo, director of the C3S.