GCP-CH4 round 3: protocols and first results of atmospheric inversions
Abstract
Atmospheric methane (CH4) has received a lot of attention in the past ten years because (i) it is the second anthropogenic greenhouse gas after CO2, responsible for about 20% of the additional radiative forcing due to human activities since the industrial revolution, (ii) its global to regional decadal budgets and their evolution remain largely uncertain and (iii) it offers interesting opportunities for climate change mitigation.
Atmospheric methane observations include in-situ measurements and remote-sensed data from the surface or from space. These data are assimilated in atmospheric inversion to infer methane emissions and sinks (top-down approaches). In parallel, a large international effort is conducted to model emitting processes emitting methane at the surface (e.g. wetland emissions) or destroying methane in the atmosphere (e.g. OH radicals), but also to compile inventories of anthropogenic emissions (bottom-up approaches). The Global Carbon project-CH4 has already released two global methane budgets in 2013 and 2016. Two protocols have been designed for the next assessment of the global methane budget from top down and bottom-up perspectives, covering the time period 2000-2017. Here, we present the protocols and the first results inferred from atmospheric inversions. Atmospheric measured trends are first reviewed, showing an widely spread increase among latitudes since 2014. Then, a focus is made on the explanation in terms of surface emissions and atmospheric sinks of the sustained atmospheric growth rate since 2007.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B43D..01B
- Keywords:
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- 0426 Biosphere/atmosphere interactions;
- BIOGEOSCIENCESDE: 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCESDE: 0497 Wetlands;
- BIOGEOSCIENCESDE: 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE