A ground-breaking study led by Prof. Jayanarayanan Kuttippurath from the Centre for Ocean, River, Atmosphere and Land Sciences (CORAL) at the Indian Institute of Technology Kharagpur (IIT-Kharagpur), in collaboration with international researchers, has refuted previous claims of a severe ozone hole in the tropical stratosphere. The study provides reassurance that there is no significant ozone depletion in the tropics and no associated health threat.
The recent study entitled “No Severe Ozone Depletion in the Tropical Stratosphere in Recent Decades,” challenges earlier assertions of a year-round massive ozone hole in the tropics. The previous research suggested that such an ozone hole could potentially impact the health of about half of the world’s population residing in tropical regions.
Stratospheric ozone is an important constituent of the atmosphere. Significant changes in its concentrations have great consequences for the environment, ecosystems and public health. The researchers analyzed ground-based, ozonesonde and satellite ozone measurements to examine the ozone depletion and the spatiotemporal trends in ozone in the tropics during the past 5 decades (1980–2022). The amount of column ozone in the tropics is relatively small compared to high and mid-latitudes. In addition, the tropical total ozone trend is very small as estimated for the period 1998–2022. No observational evidence is found regarding the indications or signatures of severe stratospheric ozone depletion in the tropics in contrast to a recent claim. Also, the current understanding and observational evidence do not provide any support for the possibility of an ozone hole occurring outside Antarctica today with respect to the present-day stratospheric halogen levels.
Figure 1: The distribution of Total Column Ozone (TCO in DU) averaged over the tropics (30° S–30° N) from different satellites from 1978 to 2022. The light lines show the monthly distribution, whereas dark lines show the annually averaged value of TCO. The dotted line shows the decadal distribution of TCO from MERRA–2 and ERA–5.
Key Findings of the IIT-Kharagpur Study:
- No Evidence of Ozone Hole: The study utilized an extensive array of ground-based, satellite, and reanalysis data, revealing that there is no robust observational evidence for a significant ozone hole in the tropics. Average ozone levels in these regions remain well above the critical threshold of 220 Dobson Units used to define the ozone hole.
- Flaws in Previous Data: The earlier study that reported the ozone hole relied on inadequate data, primarily from surface to 11 km altitude, which is insufficient to accurately assess the ozone levels at the critical 15–20 km altitude. This study also identified high uncertainty and gaps in the dataset used by the previous researcher, which led to the inaccurate conclusions.
- Ozone Trends and Dynamics: The IIT-led research demonstrates that any observed decrease in tropical ozone levels is due to atmospheric dynamics, not chemical depletion. Contrary to earlier claims, the study found either a small increase or no significant trend in ozone levels in the tropical lower stratosphere.
- No Health Threat: Based on current atmospheric halogen levels, the study confirms that there is no immediate risk of an ozone hole forming outside the Polar Regions, and thus, no associated health threat to the tropical population.
“In contrast to a previous claim, our study finds that there is no ozone hole in the tropics and therefore, no health threat associated with that. Also, it is very unlikely to have an ozone hole in the tropics with respect to the current halogen levels. The average ozone values are always about 260 DU in the tropics, which is well above the ozone hole criterion of 220 DU. The slight decrease observed in the tropical ozone in recent decades is due to the changes in atmospheric dynamics, not because of chemistry, and this has also been known to scientific community for long.” said the lead author of the study, Prof. Jayanarayanan Kuttippurath, CORAL, IIT Kharagpur.
Rolf Müller, Sophie Godin-Beekmann, and Jerome Brioude, who collaborated from Germany, France, and France, respectively, also emphasized that the study’s results align with the current scientific consensus regarding ozone dynamics and atmospheric conditions.
“The study that claimed a tropical ozone hole used data from surface to 11 km altitude, which are insufficient to assess ozone distribution at 15–20 km, the core ozone region in the atmosphere. Also, the dataset used in that study has high uncertainty and large gaps, which make it unfit to claim any scientific finding. On the other hand, we have used all then available datasets in the tropical region and found that there is no severe ozone depletion,” stated the Research Scholar and author of the study G S Gopikrishnan, CORAL, IIT Kharagpur.
Prof. Jayanarayanan Kuttippurath Mr. G S Gopikrishnan
Associate Professor, CORAL Research Scholar, CORAL
IIT Kharagpur IIT Kharagpur
“Ozone holes are confined to Antarctica due to unique condition such as extreme cold temperatures, strong polar vortex and presence of polar stratospheric clouds for 4-5 months, and this particular state of the atmosphere is absent in the tropics. Ozone dynamics in the tropics is primarily influenced by atmospheric circulation patterns. Thus, the study that claimed a tropical ozone hole is based on a flawed theoretical framework and inadequate measurements.” added, Prof. Kuttippurath.
For more details, please refer to the full study: “No Severe Ozone Depletion in the Tropical Stratosphere in Recent Decades” published in Atmospheric Chemistry and Physics.
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Pic : Inaugural session of the Indo-US SPARC Workshop (L-R) – Professor Warren D. Seider from the University of Pennsylvania was present online; Prof. Amit Patra, Deputy Director, IIT Kharagpur; Prof. N. R. Jana, HOD, Department of Biotechnology and Prof. Ramkrishna Sen, Department of Biotechnology (Convener) were present physically for the inauguration ceremony.
“Vetiver grass was used as a boundary for the plantation to check migration of nutrients. This grass if grown over the slopes of the slag dumps will further check the fugitive emissions and thereby reducing air pollution and erosion of slag onto adjacent habitations,” he added.
“I have tried to unfold ways in which this reclaimed urban space could determine, and in turn, could get determined by political fate, economic calculations and social livelihoods across changing political-economic imperatives and with large-scale implications on urban sustainability. Employing historical urban political ecology (HUPE) as the methodological framework by combining urban environmental history and urban political ecology, I have studied the changing urban environmental equations through several centuries, and their impact on the city and its people,” says Dr. Mukherjee.
In the book, Dr. Mukherjee has woven the past, present and posterity of deltaic Kolkata and demonstrated that it is in these ‘blue infrastructures’ that the anecdote of origin, the account of functioning and the apprehension of survival of the city is rooted. By emphasizing the ecology ‘of’ cities instead of ecology ‘in’ cities’ approach, she exposes the limitations of contemporary ecological restructuring efforts regarding Indian cities. Further, it offers a blueprint for future innovative and empirical research focusing on other major cities.
Paper cups are usually lined by a thin layer of hydrophobic film which is made of mostly plastic (polyethylene) and sometimes co-polymers to hold the liquid in the paper cup. Within 15 minutes this microplastic layer degrades as a reaction to hot water, says the first of its kind study conducted in India by Dr. Sudha Goel, Associate Professor at the Dept. of Civil Engineering and research scholars Ved Prakash Ranjan and Anuja Joseph studying Environmental Engineering and Management. 
The researchers followed two different procedures – in the first process, hot ultrapure (MilliQ) water (85–90 ◦C; pH~6.9) was poured into the disposable paper cups, and it was allowed to sit for 15 mins. The homogeneously mixed water was then analyzed for the presence of microplastics as well as additional ions that may have leached into the liquid from the paper cups. In the second process, paper cups were initially dipped in lukewarm (30–40 °C) MilliQ water (pH~6.9). Thereafter the hydrophobic film was carefully separated from the paper layer and exposed to hot MilliQ water (85–90 °C; pH~6.9) for 15 mins. and Changes in the physical, chemical, and mechanical properties of the plastic films were examined before and after exposure to hot water.
Explaining the exposure of 15 minutes, Prof. Goel linked its basis to a survey wherein the respondents confirmed consuming their beverage within 15 mins of obtaining it. 
The samples of paper cups were collected from popular stores across Kharagpur, West Bengal. “Our study indicates most plastic layers lining the paper cups were of HDPE (High-density polyethylene) grade, whereas only very few paper cups were lined with a copolymer of cellulose. However, the release of microplastics into the hot water was consistent in all samples irrespective of their grades,” remarked researcher Ved Prakash Ranjan. 
“Our hypothesis on the degradation of the plastic layer after exposure to hot water was confirmed through images obtained from the atomic force and scanning electron microscopy. Also, another study on the mechanical properties of the plastic film proved its deformation upon exposure to heat,” explained researcher Anuja Joseph.
“The silica extracted on purification has the potential of commercial grade silica which can further be used for production of metallurgical and solar grade silicon, confirmed the researchers,” said lead researcher Prof. A K Datta.