Abstract
Changes in tropical wetland, ruminant or rice emissions are thought to have played a role in recent variations in atmospheric methane (CH4) concentrations. India has the world’s largest ruminant population and produces ~ 20% of the world’s rice. Therefore, changes in these sources could have significant implications for global warming. Here, we infer India’s CH4 emissions for the period 2010–2015 using a combination of satellite, surface and aircraft data. We apply a high-resolution atmospheric transport model to simulate data from these platforms to infer fluxes at sub-national scales and to quantify changes in rice emissions. We find that average emissions over this period are 22.0 (19.6–24.3) Tg yr−1, which is consistent with the emissions reported by India to the United Framework Convention on Climate Change. Annual emissions have not changed significantly (0.2 ± 0.7 Tg yr−1) between 2010 and 2015, suggesting that major CH4 sources did not change appreciably. These findings are in contrast to another major economy, China, which has shown significant growth in recent years due to increasing fossil fuel emissions. However, the trend in a global emission inventory has been overestimated for China due to incorrect rate of fossil fuel growth. Here, we find growth has been overestimated in India but likely due to ruminant and waste sectors.
Highlights
Changes in tropical wetland, ruminant or rice emissions are thought to have played a role in recent variations in atmospheric methane (CH4) concentrations
We used a combination of satellite, aircraft and surface observations (Supplementary Fig. 1) between 2010 and 2015 to quantify CH4 emissions from India and to investigate sources of discrepancies between the top-down derived emissions and two inventories, EDGAR2010 (Emissions Database for Global Atmospheric Research v4.2 FT 20105) and India’s BUR (First Biennial Update Report to its National Communications6)
We find that annual emissions did not change significantly between 2010 and 2015 (0.2 ± 0.7 Tg yr−1), suggesting that the major CH4 sources, including ruminants, rice paddies, waste and fossil fuels, did not vary appreciably during this period
Summary
Ruminant or rice emissions are thought to have played a role in recent variations in atmospheric methane (CH4) concentrations. We used a combination of satellite, aircraft and surface observations (Supplementary Fig. 1) between 2010 and 2015 to quantify CH4 emissions from India and to investigate sources of discrepancies between the top-down derived emissions and two inventories, EDGAR2010 (Emissions Database for Global Atmospheric Research v4.2 FT 20105) and India’s BUR (First Biennial Update Report to its National Communications[6]). We estimate average emissions over the period 2010–2015 to be 22.0 (19.6–24.3) Tg yr−1 These emissions are consistent with India’s reports to the United Nations Framework Convention on Climate Change (UNFCCC), but are ~ 30% smaller than the most widely used global CH4 inventory, EDGAR and ~ 40% smaller than previous atmospheric inversion studies over India[14]. We find that annual emissions did not change significantly between 2010 and 2015 (0.2 ± 0.7 Tg yr−1), suggesting that the major CH4 sources, including ruminants, rice paddies, waste and fossil fuels, did not vary appreciably during this period
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