The recent heatwave in May set alarming monthly temperature records across Europe, with June marking the hottest month ever recorded in Western Europe. As we enter July, another heatwave unfolds, highlighting a concerning trend—just 50 years ago, such extreme heat in June would have been virtually unheard of. However, the impact of global warming is making heat waves more frequent, prolonged, and intense.

Tragically, heat is recognized as the deadliest climate hazard, claiming the lives of around 500,000 individuals annually. Even if we achieve net-zero emissions tomorrow, this number is likely to rise due to the already elevated levels of carbon dioxide driving up global temperatures.

As Hugh Montgomery, a leading researcher at University College London, states, “This is just the beginning.” He emphasizes the ongoing severity of this situation, indicating that prolonged heat will have significant long-term consequences.

Interestingly, outside the tropics, the annual occurrence of temperatures exceeding 32°C has increased by an average of 12 days over the last fifty years. Europe, which is warming most rapidly, typically experiences intense heat stress beginning in June and extending into September—sometimes even starting as early as May.

This trend results in a growing number of individuals facing extreme heat days and heatwaves. North America, Europe, South America, and parts of Africa are now enduring up to 50 additional days of severe heat stress compared to the 1970s.

Neil Maxwell from the University of Brighton notes, “The longer a heatwave persists and the more frequent they become, the longer individuals remain in a heightened physiological state.” Such conditions can lead to increased inflammatory responses, ultimately contributing to elevated stress levels in affected individuals.

Before the year 1998, severe nighttime heat stress was rare; however, temperatures at night are now rising in regions like Western Europe, with rates increasing twice as fast as overall global warming.

The lack of cool nighttime temperatures—defined as below 20 degrees Celsius—impairs sleep quality. Persistent hot environments make it difficult for individuals to fall asleep and attain deep sleep stages. Additionally, sleep deprivation over successive nights can diminish reaction times, escalates anxiety, and increase stress levels.

In 2022, Europe faced its hottest summer on record, triggering destructive events such as wildfires across France, Portugal, and Spain. Notably, Italy’s longest river, the Po, experienced severe drought conditions, revealing remnants of wartime ships as water levels plummeted in the Danube. The UK recorded temperatures surpassing 40°C (104°F) for the first time ever.

Dreadfully, over 60,000 deaths were attributed to these extreme temperatures, with Mediterranean countries like Italy, Greece, and Spain experiencing the highest mortality rates. These nations, home to some of the oldest populations, are at a heightened risk, given that aging bodies are more sensitive to heat and vulnerable to chronic illnesses.

Montgomery warns, “Heat triggers an inflammatory response, instigating various detrimental biological reactions in the body. This exposure can be directly harmful, particularly for those already unwell.”

Since the 1970s, Europe has witnessed a 73% increase in the frequency of heat stress days followed by tropical nights, defined as exceeding 20°C. This phenomenon, referred to as “complex events,” prevents bodies from cooling down overnight, exacerbating heat stress.

Moreover, the prevalence of prolonged heat stress is rising in Europe, while Africa is now nearly three times more likely to endure extreme heat for extended periods throughout the year.

While leaders, including former US President Donald Trump, have pledged to plant millions of trees while simultaneously increasing CO2 emissions, urban forests can significantly mitigate heat. Trees not only provide shade but also release moisture into the air through evaporation, cooling their surroundings. Neighborhoods with abundant tree cover are 10°C cooler than those without.

Despite various cities initiating tree-planting initiatives to combat heat, research indicates that many areas still fall below a 30% canopy cover, insufficient to effectively counteract the urban heat island effect. More than 90% of buildings in major cities like Paris and London remain beneath this threshold.