- In the period between winter and spring each year, Kathmandu faces severe air pollution that affects thousands of residents with health problems like burning eyes, respiratory discomfort, and even death.
- Local sources like vehicle emissions and construction dust, compounded by Kathmandu’s geography, are the main drivers of the pollution, and rising global temperatures threaten to worsen the situation.
- Changes in weather patterns, including reduced rainfall and prolonged dry periods are among the changes that could make air pollution an even more severe problem than it already is.
- Wildfires, both natural and human-induced, contribute significantly to air pollution in Kathmandu, especially during the transition period between weather systems, which could become longer due to rising temperatures.
KATHMANDU — Whenever 60-year old Saraswati Adhikari goes for a morning walk in Nepal’s capital, Kathmandu, she says she feels a certain unease in her chest. “I get a burning sensation in my eyes and nostrils and I have mucus streaming out for a long time,” says Adhikari, a diabetic whose doctor has advised her to go on walks to keep her blood sugar level in check.
Thousands of Kathmandu residents like Adhikari experience elevated levels of air pollution following the end of the winter season. At this time of the year, every year, the city ranks as one of the most polluted in the world in terms of air quality. On some of the days, it has even topped the list. Air pollution is already a major killer in Kathmandu, accounting for around 5,000 deaths a year in a city of around 1.4 million people.
The main drivers of this pollution are emissions from vehicles and factories and dust from construction work, exacerbated by the city’s location in a bowl-like valley that leads to thermal inversion, which traps airborne pollutants close to the ground. Researchers warn that rising global temperatures could potentially amplify the problem.
“In the short term, the level of pollution in Kathmandu is determined by the amount of rainfall it receives,” says climatologist Sudeep Thakuri. In general, the more rainfall, the better the air quality, as the precipitation flushes the pollutants out of the air. “However, the amount and frequency of rainfall in Nepal has been changing due to rising temperatures,” Thakuri tells Mongabay.
According to the 2023 Air Quality Report by monitoring platform IQAir lists Kathmandu as the 11th most polluted city in the world last year in terms of weighted average concentration of PM2.5, a form of particulate matter that’s so small it can be inhaled. Similarly, Nepal ranks eighth on the list of most polluted countries in the world for the same metric.
“Our research has shown that rising temperatures may lead to weaker precipitation and warmer winter and spring seasons,” Thakuri says.
Such a scenario doesn’t bode well for Kathmandu in particular and Nepal in general, which relies on two weather systems for rain during winter and summer.
During winter, rain clouds moving east from the Mediterranean bring rains to the western and central parts of the country, including at times Kathmandu. During the summer, the monsoon rain clouds moving west from the Bay of Bengal bring rainfall to eastern and central Nepal, and at times western Nepal. However, both systems have become less predictable due to climate change.
Researchers in neighboring India say they believe the frequency of western disturbances in South Asia is declining and not carrying much moisture to induce rain in lower altitudes and snow at higher elevations in recent years. Another study says that rising temperatures could lead to an increase in frequency and duration of western disturbances in the long run, but that hasn’t been observed in the last few years, and there seems to be a general agreement that climate change is making westerly disturbances hard to forecast.
Anecdotal evidence from Kathmandu residents suggests the spring drought period, when the western clouds have left South Asia and the eastern monsoon is yet to develop, is getting longer. Pre-monsoon rains, induced by locally developed systems, have also been elusive this year.
Similarly, the prevalence of El Niño conditions in the Pacific has also been observed to bring below average rainfall in South Asia, including Nepal. According to researchers, rising global temperatures could induce extreme weather events linked to El Niño.
Back in Nepal, as the air dries up and temperatures soar, the threat of wildfires around the country, known for its successful community-based forest conservation efforts, increases dramatically, especially in April. While some of the fires have been attributed to human activities — farmers burning hay and wheat husks to increase the fertility of their soil — others start naturally. India also faces a similar situation.
The Intergovernmental Panel on Climate Change (IPCC) has also long been saying that incidents of forest fires are likely to increase in a warming world.
In Nepal, as in India, when the wildfires rage, the concentration of pollutants in the air goes up significantly. “The pollutant we need to worry about is black carbon,” says air quality specialist Bhupendra Das. Black carbon, or soot, is believed to increase air temperature in the short term.
Another recently published study suggests that wildfire smoke could be leading to increases in PM2.5 levels in Kathmandu during the gap period between westerly activity and the onset of the monsoon. The study, which used satellite data and air trajectory models to study the association between PM2.5 levels in Kathmandu between 2018-2022, found that significantly high levels of the pollutant could be attributed to wildfire smoke from neighboring and transboundary areas.
This underscores the nature of air pollution as both a local and a regional and global problem, Das says. Therefore, controlling local sources of pollution in a city like Kathmandu may not be enough.
Conservationist Rajendra Narayan Suwal, who spoke at a recent event in Kathmandu to discuss the problem, said better management of forests in the region also needs to be incorporated into measures to control air pollution. He added that community forest users should be made aware about fire control measures and about the harm that slash-and-burn farming can bring to human health and the environment.
The association between rising temperatures and air pollution means that if countries around the world make an effort to control air pollution, it will have positive impacts on emissions as well, Das says. However, he notes, there’s a tendency to look at the two issues as being separate from each other.
Meanwhile, Adhikari says she checked the weather app on her phone every day, looking for the possibility of rain. “It says there is zero possibility of rain,” she says. “With the monsoon a full two months away, I don’t know how long I can live with my respiratory problems.”
Banner image: Morning view in Kathmandu. Image courtesy of Bishal Sigdel via Wikimedia Commons (CC BY-SA 4.0).
Abhaya Raj Joshi is a staff writer for Nepal at Mongabay. Find him on 𝕏 @arj272.
Citations:
Kuikel, S., Pokharel, B., & Bhattarai, N. (2024). The effect of wildfires on air quality in Kathmandu, Nepal. Environmental Advances, 15, 100493. doi:10.1016/j.envadv.2024.100493
Hunt, K. M. R. (2024). Increasing frequency and lengthening season of western disturbances are linked to increasing strength and delayed northward migration of the subtropical jet. Weather and Climate Dynamics, 5(1), 345-356. doi:10.5194/wcd-5-345-2024
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