State and Trends of the Global Carbon Budget
Abstract
Long-term redistribution of carbon among fossil fuel reserves, the atmosphere, oceans and land largely determines the degree of the human perturbation of the atmosphere and the climate system. Here I'll show a number of diagnostics to characterize changes in the global carbon cycle, including: 1) the continued growth in atmospheric CO2 despite an apparent stabilization in the growth of fossil fuel emissions and the likely emissions decline from land use change; 2) the growth in the land and ocean sinks in response to the rise in excess atmospheric CO2 with large annual and decadal variability; and 3) key drivers of these trends including the global greening, spatial distribution of carbons sinks, and responses to inter-annual variability. Efforts to attribute driving processes to the growing sinks require a strong CO2 fertilization effect on vegetation growth and emerging trends show an under realized role of semiarid regions in contributing to the mean, trend and variability of the global land sink. Climate variability, including ENSO and the 2000's slowdown in terrestrial global warming, has produced opportunities to explore the drivers of global carbon fluxes as they take large departures from mean states (e.g., high rates of atmospheric CO2 accumulation along with no growth in fossil fuel emissions and strong land greening trends in recent years). Process attribution shows the strong interplay between gross primary productivity and heterotrophic respiration in response to warming, and the role of tropical and sub-tropical systems to the overall sink. New advances in observations and data handling are critical in reducing uncertainties including 1) Bayesian fusion approaches to optimally combine multiple data streams of ocean and land uptake, and fossil fuel and land use change emissions; 2) continuous landscape carbon density measurements and column CO2 from remotely sensed platforms; and 3) improved ocean circulation and CO2 uptake at the decadal scales; among others. This presentation builds upon the work done by a team of international scientists under the umbrella of the Global Carbon Project.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFMGC13N..03C
- Keywords:
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- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE;
- 1631 Land/atmosphere interactions;
- GLOBAL CHANGE;
- 1699 General or miscellaneous;
- GLOBAL CHANGE