Country scale analysis of natural and anthropogenic methane emissions with a high-resolution inverse model using GOSAT and ground-based observations
Authors: Janardanan Rajesh , Maksyutov Shamil , Tsuruta Aki , Wang Fenjuan , Tiwari Yogesh , Valsala Vinu , Ito Akihiko , Yoshida Yukio , Kaiser Johannes , Janssens-Maenhout Greet , Matsunaga Tsuneo ,   observation group
Published: March 2020

&lt;p&gt;Here, we present the results of a global high-resolution inversion study of methane emissions and their analysis for the large emitting countries. We employ a global high-resolution inverse model to optimize CH&lt;sub&gt;4&lt;/sub&gt; emissions using Greenhouse gas Observing Satellite (GOSAT) and surface observation data over the 2011-2017 period for the two main source categories of anthropogenic and natural emissions. As prior emissions, we used the Emission Database for Global Atmospheric Research (EDGAR v4.3.2) for anthropogenic methane emission, scaled by country to match the national emissions reported to the United Nations Framework Convention on Climate Change (UNFCCC). Wetland and soil sink prior fluxes were simulated using Vegetation Integrative Simulator of Trace gases (VISIT) model. Biomass burning prior fluxes were provided by the Global Fire Assimilation System (GFAS). We estimate a global total anthropogenic and natural methane emissions of 340.9 Tg CH&lt;sub&gt;4&lt;/sub&gt; yr&lt;sup&gt;-1&lt;/sup&gt; and 232.5 Tg CH&lt;sub&gt;4&lt;/sub&gt; yr&lt;sup&gt;-1&lt;/sup&gt;, respectively. This agrees with recent Global Carbon Project (GCP) estimates of 357 and 215 Tg CH&lt;sub&gt;4&lt;/sub&gt; yr&lt;sup&gt;-1&lt;/sup&gt;, respectively. Country-scale analysis of the estimated anthropogenic emissions shows that for all the top-emitting countries, differences with their respective nationally reported inventories are within the uncertainty range of the inventories. Large emitting countries such as China, Russia and the United States have mean estimated anthropogenic emission of 45.7&amp;#177;8.6, 31.9&amp;#177;7.8 and 29.8&amp;#177;7.8 Tg CH&lt;sub&gt;4&lt;/sub&gt; yr&lt;sup&gt;-1 &lt;/sup&gt;respectively. For natural emissions, we estimate large emissions for Brazil (39.8&amp;#177;12.4 Tg CH&lt;sub&gt;4&lt;/sub&gt; yr&lt;sup&gt;-1&lt;/sup&gt;), the United States (25.9&amp;#177;8.3 Tg CH&lt;sub&gt;4&lt;/sub&gt; yr&lt;sup&gt;-1&lt;/sup&gt;), Russia (13.2&amp;#177;9.3 Tg CH&lt;sub&gt;4&lt;/sub&gt; yr&lt;sup&gt;-1&lt;/sup&gt;), India (12.3&amp;#177;6.4 Tg CH&lt;sub&gt;4&lt;/sub&gt; yr&lt;sup&gt;-1&lt;/sup&gt;), and Canada (12.2&amp;#177;5.1 Tg CH&lt;sub&gt;4&lt;/sub&gt; yr&lt;sup&gt;-1&lt;/sup&gt;). In both emission categories, natural and anthropogenic, the major emitting countries all had model corrections to their emissions that were within the uncertainty range of the inventories and the inverse model uncertainty. As a special case, we evaluate anthropogenic emissions estimated for India (24.2&amp;#177;5.3 Tg yr&lt;sup&gt;-1&lt;/sup&gt;) with aircraft observation data over urban regions over India. On average, the optimized profiles showed a better match with the observations compared to the prior profile confirming improved estimates by the model for India.&lt;/p&gt;