• Cold nights and days have decreased by 4-fold from 1980 to 2020 in India.

• Warm nights and warm days would rise nearly 7-fold in the far-future (2080–2100).

• Warm nights and warm days would increase 10–13 days/dec from 2015 to 2100.

• The number of cold nights (days) would reduce by 6 (4) times by end of the century.

 Positive trend in tropospheric ozone  up to 0.35 DU yr−1 in the west and north Third Pole.

• Highest tropospheric ozone trends up to 0.2–0.35 DU yr−1 in summer in the Third Pole.

•  Tropospheric ozone contributes to a radiative forcing up to 0.3 Wm-2 in the Third Pole.

• Ozone-induced temperature rise is about 0.4 °C in the Third Pole during 2005–2020.

• Higher aerosol uptake enhances radical sinks, increasing surface ozone levels by 40–60% in 2018.

• North America, Europe and East-Asia remain under an aerosol-inhibited photochemical regime (AIR) in future scenarios.

• However, total AIR extent reduces in both near and distant future simulations.

• Annual ozone varies between 20 and 30 μg/m3, but in pre-monsoon it often exceeds 70 μg/m3

• Populated areas have high ozone exposure, above 70 μg/m3, about 10–15 days in 2022.

• Mortality due to ozone exposure in India exceeds 50000 in the year 2022 alone.

• It costs an economic burden of US $16.83 Bn in 2022; 1.5 times the health budget of India

• Higher PM levels in cities of Indo-Gangetic Plain and Central India (80–120 μg/m3)

• 17 out of 28 cities show 15–60 % decline in PM10 concentration from 2018 to 2022.

• PM2.5, NO2 and O3 are the key precursors of PM10, suggested by Random Forest model.

• The NCAP target attained cities still have 62,219 people in excess mortalities.

• This study validates TCO measurements from the Indian geostationary satellites INSAT-3D (2017–2019) and INSAT-3DR (2021–2023) by comparing them with Atmospheric Infrared Sounder (AIRS) satellite measurements and the Copernicus Atmosphere Monitoring Service (CAMS) reanalysis data. 

• INSAT-3D data have a homogenised distribution, with values generally between 265 and 270 DU, which peaks to 275 DU in the northern India. Seasonal analysis indicates the highest TCO during pre-monsoon around 280 DU and the lowest during monsoon, around 220 DU. 

• INSAT-3DR data show consistent TCO of around 240 DU over the southern peninsula, which increases to about 270–280 DU in the northernmost India. 

• In general, the INSAT measurements are accurate within ± 15–20 DU or 5–10% when compared to AIRS and CAMS data, and are comparable to that of other satellite and ground-based instruments.

• The Indian National Satellite (INSAT)-3D (January 2014–May 2017) and INSAT-3DR (January 2017–December 2021) are the geostationary weather monitoring space systems of India

• We use the collocated humidity measurements from INSAT-3D/3DR with radiosonde and the satellite-based AIRS to assess bias and Root Mean Square Difference (RMSD) in these INSAT data. 

• The bias of RH measurements in INSAT is within 10–20% for most regions when compared to the radiosonde measurements, and 10–15% with respect to the AIRS observations. 

• In general, the accuracy of RH is within 10–20% throughout the troposphere for both INSAT-3D and INSAT-3DR measurements and thus, they are suitable for scientific analysis.

• Tropospheric ozone (TPO) is significantly rising in the global tropics (0.2–0.4 DU/yr).

• TPO shows regional insignificant negative trends in the southern hemisphere (0.1–0.2 DU/yr).

• Multi-Linear Regression can explain 95% variability of tropical tropospheric ozone.

• Ozone induced radiative forcing (RF) in the tropics is within the range ±0.5 W/m2.

• Ozone-driven RF makes a temperature rise of 0.2–0.3 °C from 2006 to 2020

• Significant positive trends are found in NO₂ globally, except in the USA and Europe

• Most cities in the USA and Europe show a decline in NO₂, at about -0.1 × 1015 molec./cm2/yr

• NO₂ pollution is rising in the cities of developing country cities; a threat to their sustainability

• Strict vehicular emission norms led to the reduction of NO₂ in the USA and Europe

• Stratospheric ozone is an important constituent of the atmosphere. Significant changes in its concentrations have great consequences for the environment in general and for ecosystems in particular

• The amount of column ozone in the tropics is relatively small (250–270 DU) compared to high and mid-latitudes 

• In addition, the tropical total ozone trend is very small , as estimated for the period 1998–2022. 

• 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.

• High amounts of atmospheric NH₃ are observed in the south TP, near IGP.

• There is a significant positive trend in CO in the inner regions of TP.

• Measurements and emission inventory reveal high anthropogenic activities in TP.

• Policies are needed in high mountain regions to control the air pollution there.

• Frequency of 8 h ozone exposure exceeding 100 ppb/year reduced after NCAP implementation.

• Most stations show negative trends in surface ozone (0–0.03 ppb month−1) from 2018 to 2022.

• Most cities, except in winter, shows an NOx-limited regime, where O3 production is limited by NOx.

• Some cities show positive ozone trends; indicating the need for tailored mitigation strategies.

• This study makes use of collocated measurements of INSAT-3D and INSAT-3DR with those from 18 radiosondes, Atmospheric Infrared Sounder (AIRS), and reanalysis data within the troposphere (1,000–100 hPa) to validate INSAT temperature profiles

• Daytime temperature retrievals from INSAT‐3DR have been improved by 0.5–1 K

• Nighttime observations have a similar bias (1–2 K) and RMSD for both INSAT‐3D and 3DR

• We investigate the long-term trends of surface temperature in India using surface, satellite and reanalysis data for the period of 1980–2020

• The highest mean surface temperatures are observed in the southern India and the lowest in Himalaya  

• Analyses with the Coupled Model Intercomparison Project 6 (CMIP6) results show that temperature can increase up to 1.1–5.1 °C by year 2100 under the Shared Socioeconomic Pathways (SSP5)–8.5 scenario.

• High concentrations of tropospheric ozone are found in the Indo-Gangetic Plain.  

• All regions show increasing ozone with the highest trends in the Peninsular India.  

• Highest seasonal trends are found during monsoon in all regions (0.3–0.5 DU/year).  

• Tropospheric ozone alone contributes to a radiative forcing of 0.2–0.5 W/m2.    

• This study helps to understand the connection between energy demand, air quality and meteorology.

• This comprehensive assessment on the reduction in air pollution and its impact on regional weather can assist policymakers in drafting regulations based on the experiences gained from lockdown

• The Third Pole, encompassing Hindu Kush Himalaya (HKH) and Tien Shan mountains, has been closely monitored for the past few decades because of its deteriorating environmental conditions.

• This study reveals that the inner TP, one of the most pristine regions on Earth, is getting polluted because of high anthropogenic activities within and nearby areas/cities, indicating the impact of regional development activities and socioeconomic changes in recent years.

• High temporal variability is found at the lower latitudes in seasonal to interannual scales than those at the higher latitudes; showcasing the influence of atmospheric circulation in TCO distribution.

• Change in the temperature in the high latitude glacier TP region is a concern for the water security of south Asia.

• It is inevitable to continuously monitor and analyze TCO in the region, as performed here, for the assessment of public health and climate change in the region

• Most cities show a reduction up to 15% of NO2 during the lockdown

• The unlock periods show again an increase of about 40–50% in NO2

• An increase in tropospheric O3 is observed together with the decrease in NO2

• Detailed analysis of HCHO over Indian region for the past two decades.

• High concentrations of HCHO in the Indo-Gangetic Plain and eastern India.

• Ports, cities and mining regions show increasing trends in HCHO.

• Analysis for the COVID-19 lockdown period shows significant biogenic sources.

• Severe vortex-wide ozone loss in the Arctic would expose both ecosystems and several millions of people to unhealthy ultraviolet radiation

• Sporadic occurrences of low ozone with less than 220 DU at different regions of the vortex for almost 3 weeks were found for the first time in the observed history in the Arctic

• The polar processing situation led to the first-ever appearance of loss saturation in the Arctic. 

• First detailed analysis of HCHO over Indian Ocean. 

• Significant increase in HCHO pollution over the shipping routes. 

• Indian Ocean sea route emissions are equal to that of the World Oceans. 

• A concern for public health in marine, island and coastal regions.