Heatwaves pose significant risks as one of the most perilous natural hazards. Their impact on human lives and the environment is often underestimated, necessitating greater attention and recognition. Climate change, caused by greenhouse gases from burning fossil fuels, is poised to make heatwaves longer, more intense, and more frequent.
—
A heatwave is a prolonged period of extremely hot weather, both during the day and at night. While extreme heat may not appear as visually striking as hurricanes or floods, its impacts are huge. This dangerous natural event can have widespread social, environmental, and economic repercussions as well as severely compromise human health and well-being, particularly among the most vulnerable groups of society, such as kids and the elderly, women, and those living in informal settlements.
Stress on human bodies caused by heat prevents normal daily activities and our ability to cool down properly. Areas that generally have more humidity can also put lives at risk. Sweat helps our bodies cool off, but humidity changes the way sweat evaporates from the body. Not being able to cool down puts people’s health at risk, and can lead to increased cardiovascular and respiratory complications, dehydration, heatstroke, higher blood pressure, and sleep deprivation.
Excessively hot and humid conditions can be deadly, as they affect humans’ thermoregulation, the process that maintains a steady internal body temperature – ideally between 36.5 to 37.5C – despite changes in external conditions. In other words, when the threshold – a theoretical upper limit of the human body’s adaptability to extreme heat, which scientists set at 35C – is breached, sweating will not be enough to cool off the body.
A study published in 2021 showed that approximately 489,000 heat-related deaths occurred globally each year between 2000 and 2019.
In the US, heatwaves have been by far the most lethal weather event over the past three decades. Elsewhere in the world, extreme heat has resulted in countless deaths, too. A recent study showed that in Europe alone, over 60,000 people died from heat-related stress during the 2022 summer. In the continent – which is the fastest-warming in the world – heat-related mortality has increased by around 30% in the past two decades, while heat-related deaths are estimated to have increased in 94% of the European regions monitored.
More recently, heat killed dozens of people in Southeast Asian countries including Thailand and parts of the US, while in Mecca, Saudi Arabia, more than 1,300 pilgrims lost their lives to extreme heat during the annual Hajj.
Pilgrims gathering in Mecca for the annual Hajj.
In addition to human health and well-being, heatwaves also have a significant impact on public safety, infrastructure, and the natural environment. Hot extremes have grown more intense in urban areas, exacerbating air pollution. Indeed, elevated temperatures lead to increased usage of air conditioning systems in buildings and cars, which in turn results in higher emissions and air pollution. Additionally, heatwaves can negatively impact the performance of essential infrastructures by affecting the materials used in their construction. For example, when combined with increased rainfall, extreme temperatures can accelerate the corrosion of metals and the deterioration of brick and stone materials, which, in turn, can weaken the steel structure embedded within a building’s concrete exterior.
What Causes Heatwaves?
Heatwaves typically originate from the presence of a high-pressure system, also known as an anticyclone. This atmospheric condition causes the air above a region to accumulate and compress, resulting in increased temperature and reduced moisture content. The sinking air acts as a heat dome, trapping the absorbed heat within the landscape. Simultaneously, the high-pressure system displaces cooler air and disperses clouds, allowing uninterrupted sunlight to reach the ground. As a result, the air near the ground continues to be heated persistently until it surpasses the average temperature.
Heatwaves are particularly common in dry regions like the desert Southwest and at higher altitudes, where the formation of high-pressure systems is more prone to occur.
The presence of moisture in the ground can mitigate the impact of heat, much like how sweating cools the body through evaporation. However, when ground, waterways, and vegetation retain limited water, their capacity to absorb the heat is significantly reduced, leaving the air as the primary medium for heat retention.
How Does Climate Change Intensify Heatwaves?
The world has just breached the 1.5C global warming threshold for 12 consecutive months, with June becoming the hottest June in documented history – the 13th month in a row seeing record-breaking temperatures. This increase in extreme heat is a direct result of human-made climate change. As greenhouse gas emissions trap more heat in the atmosphere, heatwaves – the deadliest type of extreme weather event – get longer and hotter.
Globally averaged monthly mean CO2 abundance since 1980. Data are still preliminary, pending recalibrations of reference gases and other quality control checks. Graph: NOAA GML.
An attribution study by World Weather Attribution (WWA) found that the heatwave affecting India and Pakistan in March 2022 was highly influenced by human-induced climate change, which made it at least 30 times more likely to occur. WWA also found that the likelihood of a 2020 heatwave affecting Siberia was 600 times higher due to climate change compared to it occurring naturally.
As Vikki Thompson, climate scientist at the University of Bristol’s Cabot Institute, explains: “Climate change is making heatwaves hotter and last longer around the world. Scientists have shown that many specific heatwaves are more intense because of human-induced climate change. The climate change signal is even detectable in the number of deaths attributed to heatwaves.”
Outdoor workers resting in the shade on a hot summer day in Hong Kong (16 August 2023). Photo: Kyle Lam/hongkongfp.com
This explanation aligns with the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), which suggests that human-caused climate change has increased the frequency and intensity of heatwaves since the 1950s and will continue to do so as the planet keeps warming.
Additional reporting: Martina Igini.
This story is funded by readers like you
Our non-profit newsroom provides climate coverage free of charge and advertising. Your one-off or monthly donations play a crucial role in supporting our operations, expanding our reach, and maintaining our editorial independence.
About EO | Mission Statement | Impact & Reach | Write for us
Featured image: Stuart Rankin/Flickr.
Images are for reference only.Images and contents gathered automatic from google or 3rd party sources.All rights on the images and contents are with their original owners.
Comments are closed.