What causes heat waves?

Year after year since 1960, a global average temperature pattern above 1°C has been observed.
image of incandescent sun
Heat waves can cause dehydration, as well as greater stress on people that can lead to heart problems. (Photo: Getty Images)

You experience a sudden change in your behavior; you have the feeling you’re playing the role of someone else. Fatigue, irritability, and sweating, although not necessarily in that order or all at once; the environment is stressful, almost hostile; and your habits change as you strive to keep cool. You’re in the midst of a heat wave.

This phenomenon is more deadly than tornadoes, hurricanes, and floods. Mexico’s third heat wave in 2023 created an inferno in 20 of its 32 states, where temperatures exceeded 40°C. This heat wave was not only atypical because of its intensity but also due to its duration.

“We overestimate our ability to react to these phenomena and underestimate the impacts climate change is causing,” says Luis Fernández Carril, a researcher on the international politics of climate change and Coordinator of Ruta Azul, Tecnológico de Monterrey’s sustainability plan.

Mexico’s third heat wave

Fernández Carril explains that what we experienced a few days ago was due to a heat dome. This is formed when high atmospheric pressure pushes warm air down and compresses it over a particular area. The mass of air accumulates in these static and arid conditions, trapping heat inside the dome.

This phenomenon can occur due to natural climate variability and is caused by multiple factors. For instance, the main cause of Mexico’s third heat wave was the Madden–Julian oscillation, an atmospheric fluctuation that inhibited the formation of clouds. This also coincided with the arrival of El Niño, which is associated with a warming of the ocean and causes heat waves, droughts, and extreme temperatures.

Although each of these events contributes to the feeling of ferocious heat, climate change is something that exacerbates the general situation.

Fernández Carril says it’s hard to state that one event in particular is due to climate change because climate emerges from statistical patterns. “It’s not about what we can see through the window, which is the weather. To see it as climate, the World Meteorological Organization (WMO) says we need at least 30 years of information.” A record over several years shows temperature patterns and the scale of weather events.

Part of everything getting complicated

Year after year since 1960, a global average temperature pattern above 1°C has been observed, which is a sign of climate change. “If you correlate the temperature with natural disasters, they increase in frequency and scale. By observing that, you can say with certainty, ‘That’s not natural; it’s anthropogenic climate change.’”

However, that’s not all; heat waves are harder to bear under certain conditions: droughts, few trees, heat islands, and zero mitigation measures.

Fernández says that part of the problem stems from constructions that are not prepared to offer the necessary thermal control for operating in academic or working environments.

Meanwhile, the researcher adds that the materials used to build houses in low-income areas are criminal. For those working outside, in construction, gardening, street cleaning, transport, and agriculture, the difficulties are greater.

The WMO report for 2022 warns that heat waves exert extra pressure on infrastructure in the electricity, water, and transport sectors.

“Climate change isn’t an environmental problem; it’s a civilizational problem, which affects every level of society. It exacerbates the problems we already have,” explains Fernández, adding that these phenomena threaten the resilience of ecosystems and organisms.

The same thing happens to human systems. Heat waves can cause dehydration and heat stroke, as well as greater stress on people that can lead to heart problems. The heat also creates ideal environments for the reproduction of flies and the diseases they pass on, spreading chikungunya and malaria to new regions.

Early warning systems and measures to mitigate effects

Although stopping climate change in its tracks is urgent, mitigating its effects is vital to the survival of society. Lancet Countdown South America says that most deaths due to heat waves could be prevented with measures for adaptation.

Fernández Carril is a lead author for the Intergovernmental Panel on Climate Change (IPCC) in the group that reviews vulnerability, impacts, and adaptation to climate change. He says that early warning systems will become increasingly important and should include an action plan for the population, decision-making agencies, health services, and workplaces.

The measures mentioned by the researcher include eliminating large expanses of concrete, filling spaces with trees, and uncovering rivers.

They also include designing constructions with materials that are suitable for tackling the environmental conditions to come. As a public policy measure at local or individual level, he mentions that it is also helpful to paint roofs white to reflect sunlight and create green roofs. The ventilation of homes is also important, which includes opening doors and windows very early and at night, not when the sun is overhead because that’s when hot air comes in.

However, these measures have their limits. Fernández says that what the IPCC states regarding heat waves is, “if the temperature reaches 1.5 degrees, that means 3.96 billion people around the world will be exposed to deadly heat waves; if it reaches 2 degrees, which will probably occur before 2050, 5.986 billion will be exposed.”

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