Global carbon cycle studies with LPJ-GUESS

Transkript

1 Navn oplægsholder Navn KUenhed Global carbon cycle studies with LPJ-GUESS Guy Schurgers University of Copenhagen Introduction LPJ-GUESS The dynamic ecosystem model LPJ-GUESS simulates biogeography (geographical distribution of plants) and biogeochemistry (carbon cycling, nitrogen cycling). EC-Earth Within EC-Earth, LPJ-GUESS will be applied to represent long-term changes in land surface conditions, fluxes of greenhouse gases (CO 2 ) and fluxes of reactive trace gases. How good is LPJ-GUESS at representing present-day carbon cycle dynamics? And what are the main changes to be expected for the future? 1

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4 Interannual variability in carbon uptake NBP and GPP compared with other models Temperature sensitivity Piao et al., Glob Change Biol, 2013 Precipitation sensitivity 4

5 Representing carbon cycle dynamics over last century release uptake Ahlström et al., Environ Res Lett, 2012 Future changes in terrestrial carbon uptake RCP 8.5 Terrestrial carbon fluxes simulated with LPJ-GUESS for 21 st century Ahlström et al., Environ Res Lett,

6 Conclusions Simulating 20 th century and present-day carbon dynamics LPJ-GUESS is well representing the magnitude and variability of the land use CO 2 flux and the residual land sink, and the net flux (NBP) explains the variability in CO 2 growth rate. Explaining terrestrial variability Marginal lands are an important driver of interannual variability in carbon uptake (and hence in interannual variability of the CO 2 growth rate). In high latitudes, warm conditions cause a large uptake. In temperate zone and tropics, uptake is large under cool and wet conditions. Terrestrial CO 2 uptake in the 21 st century For the 21 st century, CO 2 rise will enhance terrestrial CO 2 uptake (though with a decreasing efficiency), and climate change will likely decrease the terrestrial carbon storage. To constrain future changes, information on the climate sensitivity to CO 2 is more important than the actual amount of emissions. 6