I shook my head in disbelief at the headline that said Cyclone Amphan might be linked to the Covid-19 lockdown. The friend who alerted me to it was awed and outraged in equal measures.
Even a back-of-an-envelope estimate seemed to rule out the ability of human activity to forge such a disaster, which killed more than 100 people in May and left a trail of destruction in eastern India and Bangladesh.
So I reached out to one of the article’s sources, Dr V Vinoj, an assistant professor at the School of Earth, Ocean and Climate Sciences at the prestigious Indian Institute of Technology Bhubaneswar.
Vinoj introduced me to the complex world of air pollution, weather and climate, and how they interact with varying effects on different time scales.
For a start, surface-temperature changes result from two competing thermal influences. A cooling effect is caused by particles such as sulfates that block warmth from the sun. Warming is also caused by greenhouse gases such as carbon dioxide.
The catch is that the cooling by haze is short-lived and needs to be replenished continuously by regular human activities to counter the long-term warming effect of greenhouse gases due to their differing residence times in the atmosphere.
Thus particulate matter from air pollution rises and falls quickly, while greenhouse gases linger longer.
When the worldwide pandemic pushed people into their homes, vacated roads and shut industries, the cover of particulate matter over the Earth’s surface drastically rarified, allowing more solar radiation to strike the ground and water, warming them up over highly polluted regions such as South Asia.
By how much did particulate matter fall? Well, particulate levels over the Bay of Bengal have risen by about 50% since the year 2000 and will double in another 20 years at this rate. But particulates fell by about 30% to 40% because of the lockdowns.
“This lockdown’s impact on particulate pollution was substantial and should not be considered a minor incident,” Vinoj said.
This tilted the balance toward warming in the northern part of the Bay of Bengal, an area conducive to intensifying cyclones.
“The overall change in temperature over the Bay of Bengal due to lockdown was around 1 degree Celsius. Our initial estimates show that a part of this, about 0.2 to 0.4 degree, was definitely linked to a sudden decline in particulate air pollution,” Vinoj said.
“On the other hand, climate change warms the planet slowly and steadily, making it more conducive for intense cyclones year after year.”
This unexpected warming in the Bay due to a short-term clean atmosphere provided the additional impetus for the cyclone to intensify further than it might have otherwise.
Such an increase in power can mean the difference between structures staying intact and being demolished, and between life and death.
For a better understanding of the issues, he said Cyclone Fani swept through at about the same point in 2019 but failed to make it to the supercyclone category. It narrowly missed being the first supercyclone this century to form in the Bay of Bengal by a margin of about 1.5km/h.
Amphan would perhaps not have enjoyed this status if it were not for the unusual reduction in human emissions and its effects on ocean warming that drives the cyclones.
The story does not end there. Many scientists fear that the Covid-19 crisis may have warmed the planet this northern summer, thereby aggravating the melting of Arctic ice, increasing the strength of mid- and high-latitude heatwaves, and perhaps leading to wildfires.
All these effects are consequences of amplification owing to short-term changes to atmospheric particulates and are still in essence related to long-term greenhouse-gas effects.
This brings me back to my doubts about the news headline and the spreading of misunderstanding about how temperature changes can be linked to the prevention and mitigation of natural calamities.
Professor Vinoj’s takeaway is to investigate such connections and foster awareness and discussions on the tangled intricacies of human-nature interaction, rather than being blindsided by superficialities and sweeping generalizations.
He intends to pursue a full-fledged research study into these complex interactions. He asks readers to bear in mind that there is a vast multitude of diverse factors at play, gathering and shaping any natural disaster, especially something as chaotic as cyclones.
Reducing our dependence on carbon-based energy sources and moving to clean energy will go a long way in reducing our vulnerability to natural disasters in the long run.