Humanity achieved a fateful milestone last year. The European Union’s Copernicus Climate Change Service has officially declared 2024 the hottest year on record, and the first year in history with an average global temperature rising 1.5° Celsius (2.7° Fahrenheit) above the pre-industrial period — significantly increasing dangerous climate risks.

In fact, 2023 and 2024 may well be the hottest years in 100,000 years, with all indicators pointing to it getting hotter, bringing ever-worsening global impacts. “The temperature-related extreme events witnessed [last Norther Hemisphere] summer will only become more intense,” warned Samantha Burgess, deputy director of the Copernicus Climate Change Service.

In 2024, extreme heat enveloped whole regions of the world for weeks on end, with severe unprecedented consequences. A deadly heat wave killed at least 1,300 people during the annual Hajj pilgrimage in Saudi Arabia, while the worst drought in a century gripped Southern Africa, leaving 21 million children malnourished. Record drought also devastated South America, reducing Amazon rivers to their lowest levels ever recorded. North America wasn’t spared either. Heat domes — stalled high pressure systems that retain and intensify temperatures — blanketed vast parts of the U.S. and killed more than 100 people in Mexico.

But less noticed, and harder to track, is the way in which oppressive heat helps degrade air quality, making people sick. While air pollution sources are typically local or regional, the invisible hand of climate change is further deteriorating air quality around the planet.

Stubbornly persistent heat waves, record wildfires, and drastically changing wind and precipitation patterns all “alter the formation, duration and dispersion of air pollution,” notes a World Meteorological Organization bulletin, highlighting the synergistic health effects of global warming.

The Global South, an epicenter of poor air quality, is being especially hard hit. A toxic soup of air pollutants — automotive exhaust fumes over urban India, choking dust clouds blowing across Nigeria, and suffocating wildfire smoke blanketing Brazil — are being made even deadlier by a rapidly destabilizing climate.

Ozone over New Delhi

The summer of 2024 in India’s capital, New Delhi, was more brutal than any Kunal Kumar can remember. The city was trapped under the longest heat wave in 13 years. Things were so bad that Kumar, a gig worker who makes food deliveries, was forced some days to give up his outdoor income.

“Better to lose my wages and stay at home than die of a heatstroke,” he told Mongabay.

Delhi, a sprawling city in northern India, is nestled in the country’s Indo-Gangetic Plain where summer daytime temperatures average 32°C (90°F). But a series of persistent anticyclonic wind circulation events over the northern Indian Ocean, coupled with the fading El Niño, caused clockwise wind gusts to sink over the city, creating a persistent high-pressure heat dome that pushed 2024 temperatures to relentless highs.

For weeks, brutal daytime temperatures stayed above 40°C (104°F), with little respite by night. The city’s solar heat-absorbing built environment made conditions even more miserable and dangerous.

For Kumar, who spends 12 to 15 hours a day on the road making deliveries, the heat was life-threatening — as it was for the rest of the city’s 33.8 million people, many of whom work outside or lack air-conditioning. In Kumar’s cramped South Delhi neighborhood, heat radiated off the walls and street day and night in a textbook example of the urban heat island effect.

He was dehydrated and irritable most days. “Everywhere you look there’s a traffic jam in this city. Stuck in jams, under the hot sun with hot air blowing on your body; it was unbearable,” Kumar remembers.

Normally, air pollution is perceived as a winter problem in Delhi, when a thick blanket of low-altitude smog gets trapped by cool air hanging above the metropolis. That smog is mostly composed of toxic PM2.5 particulates — very tiny particles that lodge in the lungs and can cause cardiovascular and respiratory disease. Every winter, PM2.5 levels peak due to seasonal crop burning and the exploding of fireworks during the Diwali festival, turning Delhi into one of the world’s most polluted places.

But now, as global warming and urban development bring higher temperatures over the city in summer, the co-occurring impacts of intense heat and air pollution compound in less obvious but seriously unhealthful ways.

In hot summer months, the traffic jams Kumar and thousands of gig workers are stalled in every day become hotspots for toxins that include PM2.5 particulates and ground-level ozone. High up in the stratosphere, ozone plays a vital beneficial role, absorbing the sun’s harmful ultraviolet rays. But close to Earth’s surface, it’s a potent air pollutant whose insidious health impacts accrue in the body.

Ground-level ozone is formed when nitrogen oxides and volatile organic compounds (VOCs), emitted from vehicle exhausts and other combustion sources such as factories, react with sunlight. A recent analysis by the Centre for Science and Environment (CSE), a Delhi-based think tank, found that new hotspots for ground-level ozone emerged across the city over the summer. Between April and July 2024, Delhi recorded ground-level ozone readings in excess of safe limits on 102 days, often for more than 13 hours at a stretch, the analysis said. Annual PM2.5 background levels have also risen steadily, driven predominantly by an increase in transportation emissions — traffic that now worsens air pollution in winter and drives ground-level ozone in summer.

Epidemiologist Poornima Prabhakaran, director of the Centre for Health Analytics Research and Trends at Ashoka University, calls the increasing ground-level ozone trend worrying. India has the highest death burden of any nation from chronic obstructive pulmonary disease, attributable to ground-level ozone levels, according to the “State of Global Air” report published annually by U.S.-based Health Effects Institute in partnership with UNICEF; ozone killed 238,000 people in India in 2019.

People also continue breathing other toxic contaminants released from tailpipes and smokestacks. But “The impacts of [these] secondary pollutants have not been given as much attention compared to the impacts of smog and PM2.5, probably because of lack of awareness,” Prabhakaran said.

Prabhakaran is working with scientists internationally, developing databases to track the impacts of air pollution (including PM2.5 and ozone) on a variety of outcomes, such as respiratory and cognitive health functions. “We’re trying to analyze, with data, every health outcome that we can get our hands on,” Prabhakaran said, adding, “Intermediate risk factors like hypertension, high blood pressure, fasting glucose, high lipid levels — all of those cardiovascular outcomes — are known to worsen with even chronic, low-dose [air pollution] exposure.”

Clean air programs have largely failed to improve air quality in India because they’ve been incentivized for dust control, rather than reducing transport and industrial combustion — the biggest sources of contaminants year round. “Our programs need to become more multipollutant-focused, which means taking a whole basket of pollutants [into consideration] like PM2.5, nitrous oxides, and ozone, to track improvements in air quality. Not just the level of dust in the air,” said Anumita Roychowdhary, CSE’s executive director of research and advocacy.

Outdoor workers like Kumar remain very vulnerable to impacts due to their extensive exposure. The Indian government views the booming gig economy positively as an employment generator, at a time when unemployment rates have reached record highs. But those jobs often come at a considerable cost to workers’ long-term health.

“I try not to take days off, even when I’m sick, because it slashes my earnings,” said Kumar. But breathing Delhi’s toxic soup day in and day out could bring on disease and early death.

There’s also an economic cost. Gig workers are often primary family breadwinners, laboring without insurance or paid medical leave. A survey of 10,384 app-based workers across India conducted by the People’s Association in Grassroots Action and Movements and the University of Pennsylvania found that nearly 100% of respondents said they suffered physical and mental health issues due to gig work. Around 43% earned less than 500 rupees ($5.80) a day, and a similar proportion said they took no days off.

“Companies hiring us should be more humane with benefits, wages and time off,” said Kumar, adding, “We work through the rain, through the heat.” It’s heat that scientists say will only intensify in coming years.

Wildfire smoke above Brazil’s Xingu Indigenous Park

Last year, Ewésh Yawalapiti Waurá says he watched helplessly as drought shrank away the life-giving waters of the river near his native village in Xingu Indigenous Park. Flowing through Brazil’s Amazon Rainforest, the Xingu River and its tributaries are vital to the territory’s 16 Indigenous groups.

But drought wasn’t the only challenge faced by residents in 2024: As the river receded below, thick plumes of choking smoke hung overhead, the result of raging wildfires described as the worst the region has seen in recent years.

Xingu Indigenous Park is located where the Amazon Rainforest biome transitions to the tropical Cerrado savanna biome in the central Brazilian state of Mato Grosso. The park, a protected area, was created in 1961 to preserve Indigenous culture and natural biodiversity. Waurá is the executive director of the Xingu Indigenous Land Association (ATIX), a group formed in 1994 to defend the rights of Indigenous peoples living in the Xingu region.

But how, does one protect the people from deadly wildfire smoke? In the past, “it was easy to control the fire[s]. Today any fire gets out of control, spreads out; it’s difficult to control,” Waurá told Mongabay in a video interview. More than 200 firefighters from IBAMA, Brazil’s environmental agency, were sent to douse fires in the Xingu territory last year, with more volunteers joining them in “full force.” But the blazes remained “really out of control,” Waurá said. The local landscape has changed dramatically in recent years, Waurá added. Climate change and deforestation for agribusiness expansion have combined to dry out the region, destroying the remaining rainforest’s ability to resist fire.

Wildfires set by land grabbers and farmers to clear new pasture and croplands, have crawled ever closer to the Xingu territory over the last two decades. Between 2020 and 2021, around 13,000 square kilometers (5,000 square miles) of the Amazon Rainforest were razed, a rate driven higher by former Brazilian president Jair Bolsonaro’s policies encouraging rainforest agriculture and mining.

Changing weather patterns have also made the forest far more vulnerable, experts say. “These fires occur during periods of prolonged drought, especially in El Niño years, and their effects have become more present and aggressive after deforestation around the territory has become more widespread,” said Katia Ono, an adviser on natural resource management in the Xingu region with the Instituto Socioambiental (ISA), a civil society organization working on environmental and Indigenous rights.

Satellite images revealed more than 53,620 fire outbreaks in the Amazon in 2024. The state of Mato Grosso bore one of the highest shares of these blazes, which burned for months into late September because of a delayed rainy season (a known climate change impact). The wildfires not only devastate rainforest biodiversity, but also cause health problems among Indigenous residents and other traditional peoples.

“You can’t breathe properly anymore, you can’t sleep properly, you can’t see properly — that’s what I felt when we had the forest fires,” said Takumã Kuikuro, a filmmaker and president of the Alto Xingu Family Institute, another Indigenous association. Kuikuro has made a documentary film about the Xingu Indigenous Park firefighters who joined government efforts to extinguish the uncontrolled blazes. “My mother’s sister has a respiratory problem with her lungs, and it’s getting worse and worse [because of the smoke],” he said.

Children in particular are affected by this smoke and “they end up getting the flu and having respiratory problems,” said Waurá, noting that the situation is even worse for young people with chronic respiratory problems.

An analysis of hospitalizations attributable to deforestation-related fires in the Amazon confirms that young children and people older than 60 are most frequently hospitalized. High exposures to PM2.5 particles, the most dangerous pollutant in wildfire smoke, causes inflammation and can decrease lung capacity, leading to other health problems.

Drier conditions, elevated temperatures and reduced rainfall were found to “exacerbate fire incidents [between 2009 and 2019], impacting hospital admissions for respiratory diseases at a rate as high as 22 hospital admissions per 1000 forest fire events” in the Brazilian Amazon, according to a modeling study.

Smoke exposure can occur even at great distances from fires, explained Ana Alencar, director of science at the Amazon Environmental Research Institute (IPAM). The Amazon’s “flying rivers,” a natural circulation pattern that regulates and distributes water vapor from the Atlantic Ocean across the Amazon Basin, also carries wildfire smoke.

“The circulation enters Brazil from the north, then goes towards the Andes in the west and settles in the southwest. Lots of uncontacted tribes live in these regions, which are badly affected by ashes from the smoke. The Xingu are also affected because they are surrounded by fires,” Alencar said. IPAM has set up air quality sensors in the Xingu region and discovered air pollution in some villages soared more than 50 times higher than the World Health Organisation’s recommended limits.

Record wildfires occurred in 2024 despite a sizable drop in active deforestation, pointing to the clear impacts of climate change, Alencar noted. “It means the rainforest, and not just the savanna region, is becoming more flammable,” as warming worsens.

Kuikuro equates the health of the rainforest with the health of its people. “Health is in the environment, health is in the river, health is in the land. We have to keep our forest standing, we can’t set fire to the bush, because that’s our health,” he said.

Through crowdfunding, Kuikuro said the Alto Xingu Family Institute (IFAX) has distributed internet hotspot access to Indigenous villages to track fire occurrences in the territory and to help fight wildfires near Indigenous communities. This internet connection has also been used for health and education purposes, he added.

According to Waurá, even though primary health care facilities in the Xingu park are provided by the government’s Special Secretariat for Indigenous Health (SESAI), residents still must travel to distant urban areas for more complex treatments. “The structure is never enough,” he said. “There is [also] a shortage of medication, which ends up affecting treatments that could be carried out within the community itself.”

Dust over Nigeria’s Kano

In the commercial city of Kano, Nigeria, dust is a daily part of life. “Kano is very hot. Even when there is power and the fan is running, we find it very difficult to sleep in the room [at night] due to the heat, especially during the dry season,” Zahara Usaini, a small-scale trader and 32-year-old mother of three, told Mongabay.

Located in the arid, northern part of Nigeria, Kano’s surrounding landscape is dominated by savanna grasslands. In the past, temperatures there typically rose only as high as 33°C (91°F). But last year, they reached new records — hitting 39°C (102°F), and even 41°C (106°F) in places. A prolonged heat wave, made 10 times more likely due to the effects of climate change, swept the region in 2024.

“The hotness of every dry season is increasing each year. I think it’s from God,” Usaini said.

She felt anxious as she waited at Khalifa Sheikh Isyaku Rabiu Pediatric Hospital, where her youngest child, Hauwa, had been admitted. Hauwa, just 3 years old, had developed a fever that the family initially mistook as a malaria symptom. But when she didn’t respond to treatment by a local hospital, and started to convulse and lose consciousness, Hauwa was transferred to Khalifa and given the correct diagnosis: meningitis.

Meningitis, an infectious disease caused by various viruses, bacteria and fungi, inflames the spinal cord and brain and can be fatal if left untreated. The northern part of Nigeria, where both Kano state and Kano city are located, lies in a region of sub-Saharan African dubbed the meningitis belt, stretching from Ethiopia in the east to Senegal in the west.

Here, meningitis cases tend to occur from December to May, when the Harmattan, a trade wind, carries cool, dry, dust-laden winds from the western Sahara. Northern Nigeria’s proximity to the Bodele depression, a sunken desert in northern Chad, also exposes Kano to frequent dust storms that engulf the city in a fine haze of particulates.

As temperatures rose last year, Kano health commissioner Abubakar Labaran warned that dry, hot conditions “could cause scratch in the nose, and one could contract meningitis.”

Cheikh Dione, a researcher with the École Polytechnique in Paris and a former scientist with the African Centre of Meteorological Application for Development (ACMAD), has done research aimed at forecasting meningitis outbreaks using meteorological indicators. “We found that there is a link between climate variability and meningitis occurrence over the African meningitis belt,” Dione told Mongabay.

That research determined that meningitis outbreaks tend to happen when relative humidity is low, dust loads high, and temperatures rise above 30°C (86°F). “During an outbreak of dust, we have low temperatures. One of the main conditions driving a meningitis outbreak is when temperatures increase following a dust event,” Dione explained.

There’s now mounting evidence the meningitis belt is expanding due to global warming. Deforestation and mining, both activities that accelerate desertification, could also contribute to meningitis occurrence in countries like Uganda and Angola, said Dione. According to a modeling study, cases of meningitis in northern Nigeria could increase by 47% by 2060 compared to 1990-2005 levels, even if global mean surface temperatures stay below 2°C (3.6°F) of warming.

Climate change is just one causal factor in meningitis outbreaks. Local drivers include overcrowding, poor ventilation, lack of awareness about treatments, and vaccine skepticism. Kano is Nigeria’s second most populous state, with most people living in rural areas where traditional healing methods are widely practiced and infant mortality is high.

Yusuf Abubakar, a nurse at Khalifa hospital, has noticed that meningitis occurs in the hot months, but says poverty plays a role in exposure. “People with high economic status tend to have big houses, with well-ventilated areas, maybe even 24-hour electricity,” said Abubakar, adding, “In most cases, children who present for meningitis cases [at the hospital] are more from areas where people of low socioeconomic status live.”

Meningitis necessitates hospital admission because of complexities in its treatment. When admission is delayed and the disease allowed to progress, children can be left disabled, said Zainab Garbayaro, a doctor at the Khalifa hospital. “It could be a hearing disorder or blindness or other … disorder. This means they have to be placed under rehabilitation for a while after treatment. Some of the patients never return back to normal.”

Dione says a meningitis forecasting system, like the one developed by ACMAD, will help thwart large outbreaks of the disease in the future. A forecasting system could also help health care workers plan for timely vaccinations. “There is a lot of effort in international and national institutions to defeat meningitis. If medical experts are able to anticipate outbreaks and act accordingly, they can greatly reduce infections,” he said.

The complex influences global warming is having on urban air pollution in India, wildfire smoke in the Brazilian Amazon, and meningitis outbreaks in Nigeria provide just three examples of how climate change is worsening public health worldwide.

As climate change worsens, it will continue altering our planet in unforeseen ways, opening new opportunities for disease spread, and forcing public health experts to scramble to understand and treat these maladies.

Banner image: A firefighter in the Xingu Indigenous Territory. Image courtesy of the Alto Xingu Family Institute (IFAX). 

This story was researched and written by Simrin Sirur, with inputs from Orji Sunday in Nigeria and Karla Mendes in Brazil.

As 25 Earth vital signs worsen, scientists warn of ‘irreversible climate disaster’

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