Abstract
Interannual variations in the flux of carbon dioxide (CO2) between the land surface and the atmosphere are the dominant component of interannual variations in the atmospheric CO2 growth rate. Here, we investigate the potential to predict variations in these terrestrial carbon fluxes 1–10 years in advance using a novel set of retrospective decadal forecasts of an Earth system model. We demonstrate that globally-integrated net ecosystem production (NEP) exhibits high potential predictability for 2 years following forecast initialization. This predictability exceeds that from a persistence or uninitialized forecast conducted with the same Earth system model. The potential predictability in NEP derives mainly from high predictability in ecosystem respiration, which itself is driven by vegetation carbon and soil moisture initialization. Our findings unlock the potential to forecast the terrestrial ecosystem in a changing environment.
Highlights
Excess carbon dioxide (CO2) in the atmosphere is derived primarily from fossil fuel sources (Le Quéré et al 2018a), and is the largest contributor to anthropogenic global warming to date (Myhre and Shindell 2013)
Both GPP and ER are highly sensitive to changes in the Earth system, such as internal variability imposed by the El Niño-Southern Oscillation (ENSO; Rayner et al 1999, Jones et al 2001) or external variability imposed by volcanic eruptions (Frölicher et al 2011), and increasing atmospheric CO2 concentration (Zhu et al 2016)
As globallyintegrated net ecosystem production (NEP) is a dominant contributor to variations in the land-air CO2 flux and the atmospheric CO2 growth rate, our results suggest that the atmospheric CO2 growth rate may be predictable up to two years in advance
Summary
Excess carbon dioxide (CO2) in the atmosphere is derived primarily from fossil fuel sources (Le Quéré et al 2018a), and is the largest contributor to anthropogenic global warming to date (Myhre and Shindell 2013). The governments participating in the 2015 Paris Climate Agreement pledged to prevent dangerous anthropogenic interference with the climate system by collectively reducing greenhouse gas pollution (United Nations Framework Convention on Climate Change 2015) Verification of these emission reductions from atmospheric CO2 observations is hampered by our inability to accurately quantify and predict carbon absorption by the land and ocean (Le Quéré et al 2009). The net CO2 flux from atmosphere to land is comprised of a large positive flux due to plant photosynthesis (gross primary production, GPP), a large negative flux due to plant and soil respiration (ecosystem respiration, ER), and smaller negative fluxes due to land use and disturbance (Ciais and Sabine 2013) Both GPP and ER are highly sensitive to changes in the Earth system, such as internal variability imposed by the El Niño-Southern Oscillation (ENSO; Rayner et al 1999, Jones et al 2001) or external variability imposed by volcanic eruptions (Frölicher et al 2011), and increasing atmospheric CO2 concentration (Zhu et al 2016)
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