A heatwave in May set monthly temperature records across Europe; a heatwave in June became the hottest ever observed in western Europe. Now, in July, yet another heatwave is developing. Just 50 years ago, the June heatwave would have been virtually impossible. But global warming is making heatwaves more frequent, longer and more intense.

Worldwide, heat is the deadliest type of weather, killing more than each year. The number will increase, since even if we reached net zero tomorrow, the carbon dioxide we have already emitted will keep raising temperatures.

“This is just the start,” says at University College London. “Things are unfolding in a very, very major way now, because this isn’t just about it [being] too hot in London, and the long-term effects are going to be savage.”

Outside the tropics, the time of the year in which temperatures above 32°°ä occur has lengthened by 12 days in the past half-century. In Europe, the fastest-warming continent, the season of strong heat stress now starts on average in June and continues until almost September. Sometimes, like this year, it starts in May.

That increases people’s exposure to hot days and heatwaves. Parts of North America, Europe, South America and Africa now experience up to 50 more days of strong heat stress compared with the 1970s.

“If you’ve got heatwaves that last longer, and then you’ve got more heatwaves, people are going to be in that raised physiological state for longer,” says Neil Maxwell at the University of Brighton, UK. “That can lead to greater inflammatory marker responses, and that ultimately puts a greater stress upon individuals.”

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Strong heat stress almost never occurred at night before 1998. But now, nighttime temperatures in western Europe and other places are increasing at of global warming as a whole.

A drop in body temperature triggers sleep. If the environment is too hot, it is harder to fall asleep, as well as to enter a state of deep sleep. And loss of sleep over several nights in a row can hinder reaction time and boost anxiety and stress.

“If you don’t get cooling periods at night, which we define in this country as less than 20°°ä at night, sustained temperatures without cooling have worse impacts,” says Montgomery.

The hottest summer ever seen led to apocalyptic scenes in Europe in 2022. Wildfires broke out in France, Portugal and Spain. Italy’s longest river, the Po, ran dry in places, and wrecks of Nazi ships full of explosives were discovered as the Danube fell to record lows. In the UK, temperatures exceeded 40°°ä (104°F) for the first time.

More than 60,000 people died because of these baking temperatures. The highest mortality rates were in Mediterranean countries, which had some of the biggest temperature anomalies, with temperatures reaching higher than 40°°ä in Italy, Greece and Spain. These countries also have some of the , whose bodies aren’t as resilient to heat and who are more likely to have chronic illnesses.

“You also get inflammatory responses from heat, so heat exposure in itself triggers all sorts of bad biology in your body, basically, that is directly harmful
 and in particular in people with diseases,” says Montgomery.

The frequency of a heat stress day followed by a tropical night of at least 20°°ä has increased 73 per cent in Europe since the 1970s. These are called “compound events” because the body isn’t able to cool down and recover at night, compounding the heat stress.

Europe has also seen prolonged periods of heat stress become more common. And Africa is now almost three times more likely to suffer hot spells lasting three-quarters of the year or more.

Leaders like US President Donald Trump have made pledges to plant millions of trees while increasing CO2 emissions. But in the case of urban heat, trees can make a big difference. They create areas of shade, and they also draw moisture from the soil, which then evaporates from their leaves, cooling the environment. Neighbourhoods with tree canopies can be as much as than similar places.

But although many cities have started planting trees to deal with heat, a recent found that many still have swathes of territory below the 30 per cent canopy cover that can reduce dangerous heat island effects. More than 90 per cent of the buildings in Paris and London fall below this threshold.

I’m finding the heatwave hitting Europe really scary. It’s bad enough in itself, with many records being broken, especially for the higher nighttime temperatures that make it so much harder to cope. But I just keep thinking, “If it’s like this now, what’s it going to be like in 10, 20 or 30 years’ time?”

The answer, of course, is hotter and hotter and hotter. In the UK, national weather service the Met Office has just warned that, by 2056, there could be , with some places hitting 45°°ä (113°F). In just 30 years! I’ve seen at least one piece asking “is this the new normal?” about the current heatwave, but we’re never going to have normal in our lifetimes again – just ever more extreme heat.

It’s possible to get through even worse heatwaves than this if all your infrastructure and systems are geared up to cope. But the UK is very much not prepared. The air conditioning in Âé¶čŽ«Ăœâ€™s office, for instance, is failing to keep up with the heat as I write – and lots of people have to endure this hot weather without any air conditioning at all. In a sign of the times, a meeting on adapting to extreme heat – part of London Climate Action Week – got .

Climate scientists are continually warning of the need to prepare for hotter heatwaves, worse droughts, more flooding and rising seas. During heatwaves like this one, they might even get a little media coverage. But then the weather cools, the news agenda moves on and nothing is ever done.

That’s not just my view – it’s the official verdict of the UK’s Climate Change Committee, which advises the UK government. “Adaptation progress is either too slow, has stalled, or is heading in the wrong direction,” it said in last year. Everyone seems to assume this green and pleasant land is going to remain green and pleasant, but it won’t. We’re heading towards catastrophe, but never looking up.

There are many aspects of this that frighten me. Firstly, emissions are still rising, so the fundamental cause of the problem is getting worse. True, it’s not getting worse as fast as it was, but we are currently , and possibly even more.

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Even these alarming numbers are a little misleading because the oceans that cover most of the planet don’t warm as fast as the land. Average land temperatures are therefore going to go up by a lot more than the above numbers imply.

And what really matters to us is extreme weather, not the average. The projections for future extremes are already dire, and there are reasons to think that we’re in for extremes even greater than those currently projected for a given level of warming. For starters, heatwaves are already more extreme than projected in some parts of the world. One reason for this is that climate models may not be capturing how the dynamics of the jet streams change in a warmer world. Another is that regional models haven’t accounted for reductions in sunlight-blocking air pollution.

The next level beyond is how bad the knock-on effects of this extreme weather will be. These kinds of things are very difficult to project because so many complex systems are involved, but here, too, there is reason to think we are underestimating the impacts.

Mysterious ‘cold blob’ in the Atlantic suggests the AMOC is weakening

A patch of ocean south-east of Greenland is the only place on Earth that is cooling, and it could be a sign that the warm water "conveyor belt" in the Atlantic is slowing down

For starters, we could see mass deaths even among young people as heatwaves get more extreme. Then there’s our ability to feed people, the basis of civilisation. There’s growing evidence that global warming is already hitting food production, pushing up prices and causing yet more deforestation as farmers try to compensate.

As ever more weather extremes hit the world at the same time, the economic impacts are going to get ever more serious, too. One 2024 study warned that the result could be the worst global financial crisis ever.

And I haven’t even mentioned the wild cards, such as the Amazon drying up or the Atlantic Meridional Overturning Circulation shutting down. One researcher I chatted with at a recent conference thinks a slowdown of this crucial current system around 12,000 years ago triggered extreme seasonality in places like Britain, with sweltering summers, but temperatures plummeting tens of degrees below freezing in winter.

The fact is, the world is changing fast and we need to change just about every aspect of our lives to adapt – our homes and offices, factories and schools, cars and trains, farms and gardens, and so on. But it’s not happening.  That’s why if you’re not scared witless by this heatwave, you should be.