Fast out, Slow In-Which Terrestrial Carbon Fluxes Explain the Interannual Variability of Atmospheric CO2 Growth Rate?
Abstract
Terrestrial biomass and soil together store three times as much carbon as is contained in the Earths atmosphere and recycle the equivalent of atmospheric carbon once every 10-20 years. The carbon balance of global vegetation therefore plays a major role in the climate change mitigation policies. However, global vegetation carbon fluxes are dynamic and their interannual variability (IAV) correlates with the IAV of atmospheric CO2 growth rate (CGR). Carbon fluxes of vegetation is subject to a rapid loss from disturbance (deforestation, degradation, and fire) with emissions to the atmosphere, and a slow gain from forest growth and regeneration with carbon uptake from the atmosphere. Here, we analyze carbon fluxes of vegetation from 2001-2020 to quantify which of these processes control the IAV of CGR and what are the contributions of different ecosystems globally and regionally. By focusing on the live vegetation carbon stocks (above + below) changes derived from a combination of ground, airborne, and satellite observations, we quantify the IAV of carbon fluxes by separating emissions (fast out) and uptakes (slow in). Our results show that carbon stock changes of vegetation have large IAV of 1.7 PgC year-1 globally. Overall, emissions from forest cover change and fire had relatively smaller IAV (0.4 PgC year1), while carbon removals showed larger IAV (1.8 PgC year1) with tropical, temperate and boreal having almost equal contributions to the magnitude of IAV of carbon removals. However, we find only carbon fluxes of tropical forests show a strong correlation (R=0.88) with the CGR IAV, with moist forests and dry woodlands contributing equally to the carbon correlation. Using a mass balance approach for net fluxes, we find emissions (fast out) contribute little to explaining the CGR IAV, and almost all variations are explained with vegetation carbon recovery (slow in) in secondary forests and regenerating vegetation. We show these results have significant implications for improving the condition for forest recovery for mitigating climate change.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2021
- Bibcode:
- 2021AGUFM.B53A..05S