What can we expect in the coming weeks of this scorching summer? What are these Omega-shaped heat domes? Is the super El Niño on its way? To what extent is the climate crisis really to blame for this exceptional heatwave, which saw the night of Monday 22 to Tuesday 23 June become the hottest ever recorded in France? In Italy, are temperatures expected to peak at over 40°C in the worst-affected areas, even before the start of summer? What impact will this have on health, human lives, work and the economy?
Renewable Matter sought to shed some light on the matter by interviewing Serena Giacomin, a meteorologist at MeteoExpert, at a time when many people are saying, “Well, yes, it’s always been hot in summer”, whilst emergency departments are filling up with people suffering from heatstroke and heat exhaustion.
What does the outlook hold for Europe?
Italy is being fully swept up by the advance of this ridge of the African subtropical high-pressure system, which is carrying an exceptionally hot air mass. This is the same weather pattern that is currently hitting the area between France and the United Kingdom even harder. Over the coming days, the core of the most extreme temperature anomaly will gradually shift from the Spain–France–United Kingdom axis towards Central Europe, Scandinavia and Eastern Europe. Amid this broader European weather pattern, Italy will remain under almost continuous influence at least until the beginning of July. We can therefore expect several more gruelling days. And even when this acute phase comes to an end, no cool air or lasting relief is expected: temperatures will simply return to values closer to the seasonal average. The resulting problems are those we have, unfortunately, come to know all too well, but which are now more pronounced: heatwaves and tropical nights. We will see maximum temperatures widely approaching the 40°C mark. The real danger, however, will also be at night: temperatures will struggle to drop below 24–25°C, preventing the body from cooling down and placing a heavy strain on the healthcare sector, both day and night. The freezing level will remain steadily well above 4,000 metres, dealing a severe blow to the glaciers and the entire mountain ecosystem, which is already vulnerable. The most critical factor is the duration. Our entire socio-economic system is not structurally prepared to cope with temperatures of this magnitude for two consecutive weeks, especially this early in the summer season.
The European scientific community is increasingly using the term ‘new normal’. From a climatological point of view, have we truly entered a phase where two heatwaves in June, with temperature anomalies of this magnitude, are a possible long-term norm?
From a strictly climatological perspective, the term ‘new normal’ is almost a contradiction in terms: it evokes the idea of reaching a new plateau, a changed but stabilised state. The scientific reality, unfortunately, is quite different. We are not facing a new state of stability, but a constantly rising trend. What we are witnessing is a transition towards a completely altered climate regime, in which the old ‘norm’ of the last century has now been displaced. And if we project this trend not in the long term, but already in the medium term, the answer is yes: events like this are becoming the norm for our summers. We are seeing a gradual erosion of spring, the effects of which are already evident in May, while it is June that has experienced the most pronounced rise in temperatures in recent decades. This ‘double whammy’ of heatwaves is the fingerprint of a climate system that has become much warmer, in which the temperature baseline has risen to such an extent that a single high-pressure system is enough to send thermometers soaring towards 40°C. The future holds summers that are not only hotter but structurally different, characterised by a marked persistence of these phenomena. This means that not only will we reach higher peaks, but heatwaves will tend to last much longer, just as has been happening over the past two weeks. We need to make a profound effort to change our perception, because from a climatic perspective, we have a very short memory. We must understand that 40°C in June remains an extreme event. Moreover, this month has an astronomical feature that exacerbates the heatwave: the days are the longest of the year. This means that sunshine lasts for up to 15–16 hours, allowing continuous heat to build up at ground level and leaving very few hours at night for it to dissipate. We are not facing a strange or exceptional summer, but the tangible manifestation of a climate that has shifted gears: what today appears to us as an extreme, record-breaking event may, in thirty years, be remembered as an almost… “cool” June.
Italian and French meteorologists are currently describing the formation of an Omega-shaped pattern: a robust anticyclonic ridge trapped between two areas of low pressure (one to the west of the Iberian Peninsula and one over the eastern Mediterranean) which tends to persist for several days, preventing the arrival of atmospheric disturbance. Has this atmospheric blocking pattern become more frequent or persistent as a result of climate change?
To understand the danger posed by the Omega block, we must imagine it as a gigantic barrier. It takes its name from the Greek letter precisely because of the shape assumed by the upper-air currents: a colossal central anticyclonic ridge rising northwards, flanked on either side by two areas of low pressure. While the scientific debate regarding the overall frequency of such blocking events remains open due to the complex natural variability of atmospheric circulation, there is a stronger consensus on their persistence and intensity. It is not just a question of how often it forms, but of the fact that, when it does form, it tends not to let go, transforming a period of intense heat into a crisis situation.
And is there scientific evidence that Arctic warming, by reducing the meridional temperature gradient, is weakening the jet stream and increasing the frequency of these persistent Omega-shaped patterns over Europe?
To answer this, we can start with a fundamental mechanism: Arctic amplification, which has now been extensively studied and verified. The Arctic is warming at a rate far exceeding the global average, up to three or four times faster. This is primarily due to the loss of sea ice: instead of a white, reflective surface, we now have the dark ocean, which absorbs heat rather than reflecting it. This phenomenon has a direct and inevitable impact on overall atmospheric dynamics; first and foremost, it reduces the temperature gradient along the meridians. Put simply, the temperature difference between the Pole and the Equator narrows. Since this difference is the real driving force behind the jet stream, which flows from west to east at our latitudes, reducing the gradient causes the jet stream to lose momentum. This is where the so-called meander effect kicks in: the jet stream loses its taut, linear trajectory and begins to oscillate markedly. This slowdown generates gigantic north-south undulations that tend to become stationary. From a thermodynamic perspective, the process is clear. Where the scientific community still exercises caution lies in the rigorous statistical evidence. The change currently underway is so rapid that it takes time to establish solid and irrefutable statistics, especially in a complex system rife with “background noise” such as the climate system, where many factors are at play. However, many simulations and advanced modelling studies show that this mechanism is already increasing the persistence of atmospheric blocks over Europe and, in particular, is contributing to a rise in direct incursions by the North African anticyclonic ridge into the heart of the continent. It will take further time to accumulate data before a clear trend can be established, but one thing is already certain: on a warmer planet, such a wavy jet stream results in infinitely more severe heatwaves.
El Niño: amplifier, cause, or scapegoat? The debate within the scientific community is heated. NOAA estimates a 62% probability that El Niño will emerge between June and August 2026 and persist until the end of the year, whilst the WMO puts the probability at 80%. But Italian climatologists remain cautious: is there a hard-and-fast rule that the presence of El Niño will necessarily lead to a very hot summer in Europe?
The scientific community is working on a forecast that will be gradually refined. The latest data from NOAA show that we have already moved out of a neutral phase: the El Niño signal has officially begun, although it is still very weak. Projections indicate that its peak “super” intensity will be reached between November 2026 and January 2027. This means that there is no correlation whatsoever between the onset of the phenomenon and the weather pattern observed this June in Europe. Moreover, it is worth noting that El Niño develops in the equatorial Pacific, and its link to individual European seasons is historically weak and influenced by many other local variables. However, climate statistics do show one robust signal: El Niño events are often associated with the fact that the year following their peak (in this case, 2027) can see record-breaking global mean temperatures. This happens because the phenomenon releases a colossal amount of heat from the ocean into the atmosphere. Put simply: on a global scale, there will be more energy circulating within the system. And more energy in the atmosphere potentially means a much more extreme climate. However, we must be careful with our wording: “more extreme” does not automatically and universally translate to “hotter”. It means an intensification of all weather phenomena: more intense heatwaves where high-pressure systems establish themselves, but also floods and torrential rain, alternating with one another.
Spain is recording peaks of up to 44–45°C in the inland areas of Andalusia, with tropical night-time highs above 25°C. At the same time, the WHO has declared the heatwave a “public health emergency”, noting that in the last four years alone, the heat has caused over 200,000 deaths in the European region. In France, the Golfech nuclear power station has been shut down because the water in the Garonne has exceeded 28°C (the threshold above which thermal discharges pose a risk to wildlife), with production cuts also expected at other plants. What are the most dangerous weather phenomena that this specific heatwave – which is stagnant and humid in Northern Europe and dry in the South – could trigger over the next two weeks, up until the end of the first week of July?
There are several dangerous phenomena to watch out for. This mass of extremely hot, stagnant air behaves like a giant sponge that stores energy. At the first influx of cool air or the first breakdown of the Omega-shaped high-pressure system, all this energy will be released suddenly. We will not see normal summer showers, but violent thunderstorms, hail and destructive gusts of wind. Temperatures approaching 40°C completely deplete the vegetation’s moisture content. Under these conditions, wildfires spread extremely rapidly, and the intensity of the flames may exceed the containment capacity of standard firefighting methods. The case of the Golfech nuclear power station shows that the severity of this heatwave directly impacts the economy. With river temperatures above 28°C and soils suffering from sudden drought, there is not only damage to ecosystems (fish deaths and algal blooms), but also a lack of water to cool power stations and industrial plants, just as electricity consumption for air conditioning is skyrocketing. In short, the greatest danger of this heatwave is not just the current heat, but also the persistence and severity of the phenomena it will trigger as soon as the atmosphere attempts to shift gears.
Attribution science: to what extent is this heatwave “due” to climate change? The anomaly of +8.1°C above seasonal averages recorded in France exceeds the peak of July 2019. Climatologists from the World Weather Attribution network are likely to publish an analysis in the coming weeks. Based on established attribution methodologies (such as those used for the heatwaves of 2003, 2019 and 2022), what is their estimate of the extent to which anthropogenic warming has increased the statistical probability of an event such as this?
From a methodological point of view, it is currently far too early – and scientifically incorrect – to venture precise figures or percentages. The science of attribution requires rigour: the heatwave is not yet over, and the full collection of atmospheric data is still ongoing. Before determining to what extent anthropogenic warming has increased the statistical probability of this event and its intensity, climatologists at World Weather Attribution will need to run complex climate models, comparing the real world with a model of a planet without human emissions. We will therefore have to wait for the final figures in the coming weeks. However, we can begin to paint a clear picture of what makes this heatwave scientifically unusual. Unlike other historical events that peaked over just a few days, this heatwave is defined by its marked persistence. The atmospheric block is freezing the weather pattern in place for two consecutive weeks, a factor that vastly amplifies the health and environmental impacts. Then there is the early onset. Observed temperature anomalies exceeding +8°C, with peak values above 40–44°C in early summer, are in themselves exceptional. But the truly unusual element is the temporal proximity to the first heatwave at the end of May. The fact that two major events have occurred in less than a month demonstrates that we are no longer dealing with isolated spikes but with a prolonged shift in seasonal patterns. In short, while we must rightly await the scientific analysis for the exact statistical “signature”, the physical dynamics already tell us that this heatwave exhibits characteristics of intensity and duration that, until a few years ago, would have been unthinkable for the month of June.
Cover: Serena Giacomin