COP28 is underway in Dubai and the global focus is on climate change. A debate on fossil fuels has been raging at the climate meet. Air pollution’s relationship with climate change is complex and as a result, there is often less engagement with the former. However, if humans keep burning fossil fuels and biofuels, air pollution will worsen and so will climate change. At the end of the day, cleaner air will lead to a healthier planet. It should be a global priority.
India’s vibrant capital city witnessed dangerously poor levels of air quality in November 2023, to a degree not seen in several years. The haze across Delhi was thick, and it felt as though the city was enveloped by a dark mushroom cloud. It suffered an unequalled PM2.5 level (monthly average) of 243 ug/m3, the highest since 2018 and an astonishing leap of more than 50 per cent over last year’s monthly average of 155 ug/m3. The AQI was in the “severe” category for a record 15 days this November. The rains on November 9 and 10 broke the smog canopy, which extended from Punjab and Haryana to Delhi at a transport height of around 900-950mb, reducing the “severity” of pollution.
This was the scenario at a time when stubble burning counts in North India — understood to be responsible for the deterioration in Delhi’s air quality in this period — dipped significantly, by around 20-30 per cent compared to last year. The control measures in Delhi under the Graded Response Action Plant (GRAP) and other measures were also stringent. There is no reason to believe that local emissions rose by more than 50 per cent in one year. The question, then, is: Why the November pollution haze?
Another curious data point came from the advanced version of the NIA-SAFAR model run by the National Institute of Advanced Studies. Despite November 2023 having the lowest stubble-burning count in the last several years, the monthly share of stubble burning in Delhi’s PM 2.5 was at the highest (>15 per cent) with a peak of 43 per cent on November 3. The model’s results indicate that even relatively low amounts of stubble burning made a big impact on Delhi’s air quality in this peak fire month. On the contrary, November 2022 was the least polluted in almost a decade and a higher amount of stubble burning did not make a big impact. This is a paradox scientists ought to answer for the benefit of policymakers.
The answer lies in unintended shifts in weather patterns. In India and across the globe, unusual natural changes are wreaking havoc on communities that previously never faced such events. Climate scientists call it a “new normal” but I will call it the new abnormal. Although more research is needed to firmly establish such connections, there are enough indications to believe that the new trends not only in Delhi’s air quality but across India have links with climate change. More complex is the fact that these natural shocks are not uniform and their impact differs from one climatic zone to another.
Although terms like ENSO, La Nina or El Nino are talked about in the context of the monsoon, their applications are broadening of late. In 2022, the unprecedented triple dip in La Nina played a decisive role in preventing North India from undergoing winter stagnation conditions because of which pollutants get trapped in air — the air quality improved as a result, and the city experienced its cleanest winter in nearly a decade. This year has seen the opposite so far. La Nina has gone, and we have entered the El Nino period. We are not sure what surprises are in store.
Contrary to last year, Delhi witnessed relatively calm wind conditions during November 2023 with limited and weaker western disturbances not having much impact beyond two to three days. There were no frequent spells of rain, unlike in earlier years. This, coupled with the mainly dry weather, helped in the accumulation of pollution with little dispersion. The north-north-west wind speed for a prolonged period facilitated the transport of biomass-burning particles into Delhi and surrounding regions.
Once the pollution particles were in Delhi, the holding capacity was at an all-time high due to the cooler, dryer and calmer local environment. This does not mean that the impact of other sources was insignificant. The best indigenous AQ model data suggests that on average, the transport sector contributed about 30 per cent of PM2.5 in November 2023 and around 43 per cent from other internal sources.
While extreme weather and changing climate patterns are taking a heavier toll on the planet as a whole, the frequency of severe pollution has regional impacts, threatening health and food security. That is precisely the reason that I brought up COP28 at the start of this article. The climate meet is equally relevant for the air quality community and people as a whole.
Emergency episodes, in all probability, are set to increase unless several drastic, science-backed steps are taken to target the emissions at the source — this should involve using an air shed approach to address the root cause of deteriorating air. The earlier we move from cosmetic quick fixes and geoengineering, the better.
The writer is Chair Professor, NIAS, IISc-Campus, Bengaluru and Founder, SAFAR
