What Caused the Heatwaves?

Collaboration from de General Coordination of Planning and Institutional Information

Last June, a significant part of the country experienced temperatures above normal, and in some states, temperatures exceeded 40°C (104°F), with Chihuahua being the state that almost reached 50°C (122°F).

At the time, the Ministry of Health reported that exposure to high temperatures resulted in issues such as dehydration, heatstroke, and skin burns. As of July 17th, over 150 deaths were attributed to the heatwave.

This phenomenon occurs every year between the months of March and May. In 2022, according to the National Meteorological Service, the maximum recorded temperature did not exceed 35°C (95°F). Therefore, this heatwave was considered an extraordinary event, not only due to the high temperature but also because it occurred in June, a rainy month in Mexico.

When seeking an explanation, the cause was attributed to global warming caused by ongoing human activity that increases day by day. This, combined with the drought affecting the country, results in a more intense heat island effect with a longer duration.

However, Dr. Ángel Refugio Terán Cuevas and Dr. María Eugenia Gutiérrez Castillo, researchers from the Centro Interdisciplinario de Investigaciones y Estudios sobre Medio Ambiente y Desarrollo (CIIEMAD) at the Instituto Politécnico Nacional, questioned what other factors, besides anthropogenic activity, were causing such an atypical phenomenon.

A Moment of Coincidences

"I believe that Don Goyo has something to do with this," Terán Cuevas emphasized when he began to investigate this phenomenon. On May 28th, the Popocatépetl volcano began to show increased activity, coinciding with the heatwave in the central part of the country.

Gutiérrez Castillo noted that during the days of Popocatépetl's activity, no environmental contingency was declared in Mexico City. This led them to question where the tons of emitted materials were going if they were not affecting air quality, meaning they were not detected in the troposphere—the lower layer of the atmosphere where weather phenomena occur, the water cycle takes place, and winds disperse most pollutants.

"The Popo is emitting a significant amount of materials that are reaching higher altitudes," the doctor stated, raising the question of what's important at higher altitudes for life on Earth.

The ozone layer, located in the stratosphere above the troposphere, largely filters out ultraviolet (UV) radiation from the sun and is a primary source of energy for ecosystems. However, prolonged exposure to high levels of UV radiation causes severe harm to living organisms.

Upon reviewing dispersion and transportation maps of sulfur dioxide (SO2) and observing the combination of high-pressure systems at different altitudes, Terán Cuevas noticed that SO2 is one of the main components of Popocatépetl's emissions. Furthermore, this SO2 had concentrated from the center to the Pacific and returned over the northeastern part of the country at higher altitudes.

This led to the absorption of sunlight, inhibiting surface warming both in the Pacific over Mexico's western coast and in the central and northwestern regions. Additionally, the dispersion of carbon dioxide (CO2) hindered moisture concentration in the upper atmosphere, where SO2 gathers, causing a reduction in the normal rainfall pattern.

It was also observed that the dispersion area of SO2 coincided with UV penetration. By correlating these variables (SO2 dispersion area and UV penetration), more could be inferred. Dr. Gutiérrez Castillo mentioned that, according to articles on the chemical composition of Popocatépetl's emissions, it emitted hydrogen sulfide, hydrogen fluoride, hydrogen chloride, hydrogen bromide, and silicon oxides. These chemical compounds react with the limited water in the stratosphere to form salts, known as "aerosols," which deteriorate the atmosphere.

As a result, the lingering of these gases in the upper atmosphere leads to a thinning of the ozone layer and a greater penetration of ultraviolet rays. There are hypotheses suggesting that these compounds can persist in the stratosphere, above 15 km, for years—a duration unlike in the troposphere where they move quickly due to wind or are deposited by rain. This is how some authors explain the impact of volcanic emissions on heatwaves and the inhibition of rainfall, Terán explained.

The CIIEMAD researcher emphasized that, in addition to attributing the June heatwave in Mexico to Popocatépetl's emissions, another element comes into play. "Analyzing satellite images, I noticed that a lot of air was coming from the eastern part of Africa, warm and dry winds that entered the Gulf of Mexico and reached the central region of the country. This influenced the limited precipitation, as it disrupted the water cycle by not allowing the formation of necessary moist air for rain generation."

"These winds, which are part of a natural cycle and always occur, along with Popocatépetl's activity, coincided at the right time to result in what we experienced," Gutiérrez Castillo explained.

The Earth Is Alive

Naturally, in response to such events, questions arise about the damage to human health due to the heatwave and the potential disasters that could stem from the eruption of the Popocatépetl volcano or Sahara dust, the impact of which would depend to some extent on the inequality and poverty conditions in at-risk areas.

Regarding the high levels of ultraviolet radiation due to ozone layer thinning, an increase in short- to medium-term cases of skin cancer is likely. Therefore, protective measures for the population during heatwaves should be implemented.

The Sahara winds bring tropical cyclones with them, and these follow their natural cycles depending on the moisture concentration in the country. However, the layer of gases and chemicals left in the stratosphere prevents this moisture from feeding the cyclones, leading to probably fewer rains during this year's wet season.

The fact that Popocatépetl has increased its activity and emitted materials to higher altitudes does not necessarily indicate an imminent eruption; rather, it's part of the natural processes of an active volcano. The ozone layer can regenerate, but the time it takes to do so precisely is not known. Global warming, resulting from the interplay of anthropogenic activities and the Earth's natural activity, such as volcanic eruptions, undoubtedly serves as the major trigger of the environmental crisis the world is facing. This is also increasing the likelihood of disasters, making it urgent to take measures to mitigate their effects.

Nevertheless, Dr. Gutiérrez insisted on not creating unnecessary alarms. But in a climate scenario like the one we're experiencing, how can we not? Dr. Gutiérrez and Dr. Terán also provided an answer: by understanding the Earth, realizing that it has its own life, and it will manifest itself when necessary.

It's about two sides of the same coin. On one hand, raising awareness of the effects of an anthropocentric civilization model based on excessive consumption. On the other hand, acknowledging and understanding that the Earth moves, breathes, and follows its own cycles, and humans must recognize themselves as part of this.

Selección Gaceta Politécnica #164. (July 31st, 2023). IPN Imagen Institucional: Read the full magazine in Spanish here