Increasing global ecosystem respiration between 1982 and 2015 from Earth observation-based modelling

Aim: Earth observation-based estimates of land-atmosphere exchange of carbon are essential for understanding the response of the terrestrial biosphere to climatic change and other anthropogenic forcing. Temperature, soil water content and gross primary production are the main drivers of ecosystem respiration (R-eco), and the main aims of this study are to develop an R-eco model driven by long-term global-scale Earth observations and to study R-eco spatiotemporal dynamics 1982-2015.Location: Global scale.Time Period: 1982-2015.Major Taxa StudiedTerrestrial ecosystems.Methods: We parameterized and applied a global R-eco model for 1982-2015 using novel Earth observation-based data. We studied the relationships between R-eco measured at field sites globally and land surface temperature, gross primary production and soil water content. Trends 1982-2015 were quantified, and the contributions from terrestrial regions to the spatiotemporal variability were evaluated.Results: The R-eco model (LGS-R-eco) captured the between-site and intra- and interannual variability in field-observed Reco and soil respiration well in comparison with other Earth observation-based products. The global annual R-eco was on average 105.6 +/- 2.3 Pg C for 1982-2015, which is close to 105 Pg C according to residuals of the carbon exchange processes within the global carbon budgets. The trend in global terrestrial R-eco 1982-2015 was 0.19 +/- 0.02 Pg C y-1, with the strongest positive trends found in cropland areas, whereas negative trends were primarily observed for savannah/shrublands of Southern Africa and South America. Trends were especially strong during the eighties and nineties, but substantially smaller 1998-2015.Main Conclusions: The LGS-R-eco model revealed a substantial increase in global R-eco during recent decades. However, the growth rates of global R-eco were slower during 1998-2015, partially explaining the reduced growth rates of atmospheric CO2 during this period. The LGR-R-eco product may be an essential source for studying carbon sources and sinks and functioning of the Earth system.