The disastrous consequences of global warming and climate change in recent decades have inflicted a wide-range of impacts on life of the people, their livelihood and global economy. These repercussions manifest with heightened severity and have also triggered climate-related catastrophes in India. The rise in temperature is primarily attributed to multiple factors, including the increase in carbon dioxide (CO₂), methane (CH₄), tropospheric ozone (O₃) and water vapour (H₂O), and all these are rising over India. Therefore, to find the changes in the concentrations and temporal trends of these greenhouse gases (GHGs), those are responsible for the temperature changes, we performed a detailed analysis of all these. For instance, the average annual CO₂ trend over India from 2002 to 2020 is approximately 2.1 ppm/year (Kuttippurath et al., 2022) and is comparable to its global trend. In a similar study, we also find that the CH₄ is increasing in India and the annual average trend is about 0.0765 ppm/decade (Singh et al., 2022). The other important GHG, tropospheric ozone, trend is also positive across all Indian regions, and the annual trend is about is 0.244 DU/year (Rathore et al., 2023). In brief, all three important GHGs show an increasing trend in India.

Water vapour, as a GHG, plays a distinct role in the process of global warming. Water vapour acts as an amplifier, intensifying the temperature change that has been caused by other GHGs. Despite being the most abundant GHG in the atmosphere, it is widely recognised for its positive feedback mechanism with temperature. Water vapour content over India shows a notable increase in recent decades, as indicated by values ranging from 0.1 to 0.2 kg/m²/year (Patel and Kuttippurath, 2022). The increase in GHGs, including water vapour, over India in recent decades has the potential to further amplify the rise in regional temperatures. However, there is no detailed study on temperature trends over India for recent decades. On the other hand, it is worth mentioning that most years between 2010 and 2020 have been characterised as very warm and there were also severe heat wave events. 

Therefore, we thoroughly examine the temperature trends in India for the period of 1980–2020, and also its future projections up to 2100 in the paper entitled “Enhanced surface temperature over India during 1980–2020 and future projections: causal links of the drivers and trends”. It is observed that there is a notable increase in temperature during the past four decades in India at 0.1–0.4  °C /decade, and the most recent decade exhibits a greater frequency of warmer years. The increase in temperature is highest in the northeast India and Western Himalaya, about 0.2–0.5  °C /decade. The temperature rise on the snow-clad and glacier areas of these regions is a great concern for floods and water security of the country.

The enhanced temperature in India can be due to the cumulative impact of rising GHGs, land use pattern change and increase in frequency and intensity of atmospheric and oceanic circulation processes. Most importantly, under high emission scenario, India is expected to experience more warming of about 1.1–5.1 °C at the end of 21^st century compared to the current situation, although these values are depending on the simulated models and their input. This rise in temperature in the future may cause climate problems, which can have a devastating impact on society including economy, public health and environment. Therefore, continuous monitoring and frequent regional assessments, as performed in this study, are necessary for making climate change adaptation strategies and mitigation measures.     

 REFERENCES

1. Kuttippurath, J., R. Peter, A. Singh, and S. Raj: The increasing atmospheric CO₂ over India: Comparison to global trends, iScience, https://doi.org/10.1016/j.isci.2022.104863, 2022.
2. Patel, V. and J. Kuttippurath: Significant increase in water vapour over India and Indian Ocean: Implications for tropospheric warming and regional climate forcing, Sci. Total Environ., https://doi.org/10.1016/j.scitotenv.2022.155885, 2022.
3. Rathore, A., G. S. Gopikrishnan, and J. Kuttippurath: Changes in tropospheric ozone over India: Variability, long-term trends and climate forcing, Atmos. Environ., https://doi.org/10.1016/j.atmosenv.2023.119959, 2023.
4. Singh, A., J. Kuttippurath, K. Abbhishek, S. Raj., G. Chander, S. Dixit: Biogenic link to the recent increase in atmospheric methane over India, J Environ. Manage., 289, https://doi.org/10.1016/j.jenvman.2021.112526, 2021.