Estimation of Oceanic and Land Carbon Sinks Based on the Most Recent Oxygen Budget

Abstract

Robust assessments of global carbon uptake are important for understanding Earth's carbon cycle and its response to human impacts. Here, based on the most recent oxygen budget, we presented an alternative estimate of ocean and land carbon sinks over the past few decades and future projections under climate change. For the period from 1990 to 2015, the ocean and land carbon sinks were ∼2.16 ± 0.73 and 1.37 ± 0.91 GtC/yr, respectively, which are in good agreement with the results from the Global Carbon Project (GCP). Our estimated temporal evolution of oceanic carbon uptake, however, presents a stronger decadal variation than the quasi-monotonous increase estimated by the GCP. Future projections of carbon sinks show significant discrepancies under different scenarios. At the end of this century, the ocean and land sinks will be 2.96 and 0.75 GtC/yr, respectively, under RCP4.5 (representative concentration pathways), while these values will be much larger under RCP8.5 at ∼5.70 and 3.69 GtC/yr, highlighting the vital role of the human-induced influence on the carbon cycle.