The response of terrestrial carbon fluxes in India to global climatic phenomena

A better understanding of country-scale anthropogenic carbon dioxide (CO2) emissions and natural flux estimates and the carbon-climate feedback, is critical in formulating national climate policies to attain net zero emissions. The irony is that some countries with high population density and fossil fuel emissions, such as India, which are in urgent need of developing such policies, have limited in situ observations to improve their understanding of regional carbon flux dynamics and carbon-climate interactions. Here, we use the atmospheric CO2 column observations from the Orbiting Carbon Observatory-2 (OCO-2) satellite to unravel the response of the Indian land biosphere to large-scale climatic phenomena such as El Niño-Southern Oscillation and Indian Ocean Dipole (IOD). An ensemble of global flux inverse models constrained by OCO-2 CO2 column observations indicate a reduction in CO2 uptake by the Indian terrestrial biosphere during El Niño and an enhanced uptake during La Niña and positive IOD (pIOD) events. During La Niña and pIOD events, Indian land biosphere carbon uptake could increase to up to 10% of India’s annual fossil fuel CO2 emissions. We find that the large Gross Primary Production variations, as compared to total ecosystem respiration, determined the response of net carbon flux variability to El Niño-Southern Oscillation and IOD. The contrasting response of the Indian land biosphere to these climatic events is due to the stronger sensitivity of photosynthetic CO2 uptake compared to respiration. The carbon climate constraints imposed by satellite observations over India help elucidate how biospheric uptake may offset anthropogenic emissions in the future.