Long-term Integrated Greenhouse Gas Observations in India: 2009-2023

Greenhouse gas (GHG) observations in India, initiated under IITM projects, commenced in 2009. We estimated India's CH4 emission as 24.2±5.3 Tg per year from 2011 to 2017. This estimation is 19.2% higher than India's CH4 emission (19.55 Tg per year) reported by the Govt of India in its Biennial Update Report 3 (BUR-3) to UNFCCC. In another top-down estimation using surface observations in India, average CH4 emissions in India during 2010-2015 were 22.0 Tg per year (19.6–24.3 Tg per year). This estimation was consistent with the emissions reported by India's BUR-1 report submitted to UNFCCC.  India's CH4 emission estimated by EDGAR (v4.3.2-2012) was 32.6 Tg per year, which is approximately 39% higher than the emissions reported by India's BUR-1(19.8 Tg per year), BUR-2 (20.05 Tg per year), and BUR-3 (19.55 Tg per year). We have deployed a variety of instruments across different locations and ecosystems in India to gain a deeper understanding of the variability in fossil fuel (biospheric) greenhouse gas emissions (sinks) across the country. We monitor in-situ CO₂, CH₄, CO, and H₂O concentrations and in-situ delta 13C of CO₂ and CH₄ using Picarro and in-situ delta 13C, 17O, and 18O of CO₂ using LGR Los Gatos. All these measurements are calibrated using WMO standards imported from NOAA Boulder, USA. Eddy Covariance systems are used at different ecosystems in India to monitor carbon and water exchange with the atmosphere. This study aims to provide an overarching view of the Indian Carbon Cycle by integrating these diverse observations. Furthermore, we will discuss the potential for utilizing these observations in model simulations and collaborate with the global community to enhance our understanding of the Indian Carbon Cycle.