Not very long ago, the advent of Durga Puja used to be marked by clear blue skies with fluffy cotton clouds. Kolkata markets used to buzz with Pujo fever under pleasant temperatures – the right amount of humidity with the late-autumn nip in the air.
Temperate days have always drawn a fairy-tale vibe from poets and writers through the colours of autumn and the blossoms of Spring. Alas, these days, the lived experience of the people of Kolkata is quite different – autumns have turned intensely hot and humid, not to speak of the rather frequent unseasonal downpour. On the other hand, Spring comes and goes without as much as a whiff.
Are the pleasant temperate days of autumn a thing of the past now?
Various studies indicate that the number of temperate days is dwindling in the world. According to estimates, temperate weather is expected to last for 74 days a year, which is approximately 20 per cent of the total days in a year. However, as the situation progresses, it is apparent that the number of temperate days will reduce to 8-10 days a year before the end of the 21st century.
What is a temperate day?
Experts suggest that temperate days are those days of the year when the temperature is pleasant, that refers to a climate or place which is neither extremely hot nor extremely cold. The maximum temperature fluctuates between 18-30 degrees Celsius on these days. A minimum of 74 days of temperate climate is indispensable to maintain the balance between high temperature and extreme chilly days.
To understand this phenomenon better, The Voices approached Dr. Lakshmi Narayan Satpati, Professor of Geography, Calcutta University, and Director, University Grants Commission – Human Research Development Centre. He said, “Indian warming pattern of each geographical region changes every year, which is natural, but global warming is also responsible for the same. Nowadays, springs converted to summer leading to rise in average temperature at night and during winters are quite evident.”
What are the effects?
The gradual reduction in the number of temperate days is posing a threat of imbalance to the ecological system of the world. The results are quite evident: fiercely hot and humid summers, chilly winters, or high or low precipitation leading to floods or drought. There has been a surge in thunderstorms as well these days that has taken a toll on lives. Siliguri in North Bengal has witnessed minimal snowfall even in early March for past few years clearly indicating a change to the natural climate cycle. Closer to incident, incessant rain spells in Delhi, Mumbai, and Kolkata brought the cities down to their knees. Amid posts of outrage and frustration in the social media, there were a flurry of hilarious posts comparing these Indian cities to Venice! Clearly, there is a link between the decline in the number of temperate days and the extreme weather events facing the world.
Dr. Satpati explained: “Global warming is causing climate change leading to increase in humidity, temperature, and thunderstorms. Again, rise in sea surface temperature leads to formation of cyclones that eastern India is facing every alternate year.”
“Western India, too, has significantly observed an increase in humidity in the atmosphere resulting cloudbursts – high intensity rainfall at short period that resulted inundation in Delhi. Even Uttarakhand, Ladakh, or a desert area like Rajasthan has been receiving intense rainfall for the past few years.”
An increase in the number of thunderstorms is also by-product of global warming, Dr. Satpati added. “Central India witnessed numerous thunderstorms leading to rainfall and in between monsoon season too, which is termed as embedded thunderstorms.” Embedded thunderstorms happen as sporadic events within a huge area of large-scale precipitation, and hence the name.
Measures like the lockdown or a curb on transportation solely cannot reverse global warming effects, Dr. Satpati asserted. “Global warming is a long-term phenomenon. Its effect should not be confused with the lockdown,” he warned. “Last year’s lockdown effect is a short lived experience. The pollution in urban areas are is region-centric and short-lived because of air drainage from one place to another, which resulted in cooling effect for the time being. That does not mean global warming has ended. Carbon dioxide that has been emitted for past 100 years cannot be treated overnight.”
During the COVID-19 surge, Dr. Satpati said, the movement of vehicles was comparatively less, and hence less amount of pollutant gases were emitted into the atmosphere. This ensured less heat trapping, thereby minimising urban heat island effect.
“Dr. Satpati states – “During the spurt of COVID – 19 in 2020, movement of vehicles were comparatively less hence less emission of pollutant gases in the atmosphere ensured less heat trapping thereby minimal urban heating island effect”
Apart from movement of vehicles in urban areas, rural areas where movement of vehicles remains relatively low throughout, too, enjoyed enhanced number of temperate days during lockdown.”
Although the picture looks bleak, there is still a ray of hope. Effective counter-measures, if taken in a sustainable way, could lead to the stalling or even a possible reversal of the global warming phenomenon.
Dr. Satpati says that a Representative Concentration Pathway, a trajectory for greenhouse gas emissions developed by the Intergovernmental Panel for Climate Change, for research and climate modelling, should adopt. Secondly, adaption of carbon capture method that separates carbon dioxide from emissions sources through chemical sources and recovers it in a concentrated stream, then the carbon dioxide is injected underground for permanent storage. Thirdly, the way automobile companies are shifting to electronic vehicles from petroleum will certainly help to ease up emissions by 2025 to 2030. “Evidently, there will be change in the agriculture sector, energy sector, transportation sector, and water sector. These days, emergence of many artificial technologies helps in draining carbon dioxide down from atmosphere. Such measures should be encouraged as well as the use of renewable energy,” Prof. Satpati added.
He underlines that there is an immediate need to pay attention to our lifestyle. “Our shift from sun synchronous life to energy synchronous life (where we stay awake till mid night due to emergence of technology connections) has led us to leave behind less carbon footprint. Hence, online classes, meetings, etc. should be encouraged in the future too.”
Infographics by Mousumi Diyasi
Dr Dipayan Dey, Chair – Research and Planning, South Asian Forum for Environment (SAFE), is of the view that the diminishing temperate days is grossly a consequence of climate change. “If we focus on the tropical region, then two phenomena of global warming are to be blamed – the El Niño southern oscillation (ENSO) and the Indian Ocean dipole. These are the temporal reasons wWhile the spatial reason can be rapid emergences of urban hubs due to over- usage of modern facilities like acair-conditioners, heaters etc. that have has opened up the window for heat island effect. This is a micro climatic change which changes the ambient temperature (i.e. depends on one’s perception of warmer or favourable temperature).”
The shrinking of temperate days largely depends on our perceived habits, Dr Dey explained. “If you visit rural areas, the temperature will be quite cooler and soothing than in the urban areas. Even inhabitants of rural areas will not complain about reduction of temperate days; rather, they may cite that it has shifted (i.e., earlier temperate days used to fall in the month of September; now it has shifted to the end of December or January).” So, what makes urban regions deprived of temperate days? Urban heating due to increased computerisation, cutting of trees for infrastructure work and so on leads to a local impact termed heat island effect, Dr. Dey maintains. “Our habits need a check. Ever wondered how we switch on AC even in just 30 degree Celsius! These are urban acclimatisation (adaptation). This would be impossible to relate globally unless we develop a political will to change our lifestyle. We have already crossed the no-return point of socio-economic barrier. It’s high time we limit our habits.”
The impact on rainfall, too, has been acute. Earlier, heavy rainfall happened in intervals. For example, two to three days of precipitation straight with three to four days gap. “Comparatively, rainfall in 2007 was heavier than 2021. This is due to the Indian Ocean dipole. West Bengal experienced cyclone Aila in 2009. After that, a series of cyclones like Hudhud and Bulbul struck. Last year’s Amphan was devastating, and this year, Yash and Jawad had battered the coast. The frequency of such cyclones has increased and with greater intensity as well, which was not quite usual in West Bengal. Generally, these cyclones used to hit Andhra or Orissa, or even cross over to Bangladesh. But things have taken different shape lately.”
Whether directly or indirectly, the dwindling of temperate days does impact our lives, Dr. Dey says. Reduced temperate days impacts pollination, thereby impeding the life cycle of butterflies, stalling growth of corps and so on, leading to biodiversity loss and a fall in primary productivity. This results in economic loss as well. “It has been observed that people can normally work in 22 to 25 Degrees Celsius temperature. But with fewer days of pleasant ambient temperature, people tend to lose productive approach to work causing loss in economic man days,” Dr. Dey pointed out.