The Change of Climate and Terrestrial Carbon Cycle over Tibetan Plateau in CMIP5 Models

Abstract:

Six earth system models from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are evaluated over Tibetan Plateau (TP) by comparing the modeled temperature (Tas), precipitation (Pr), net primary production (NPP) and leaf area index (LAI) with the observed Tas, Pr, IGBP NPP and MPIM LAI in the historical, and then we analyzed the change of climate and carbon cycle and explored the relationship between the carbon cycle and main climatic drivers in the historical and representative concentration pathway 4.5 (RCP4.5) simulation over TP. While model results differ, their region spatial distributions from 1971 to 2000 agree reasonably with observed Tas, Pr and proxy LAI and NPP. The climatic variables, LAI and carbon flux vary between two simulations, the ration of NPP to gross primary production (GPP) does not change much in the historical and RCP4.5 scenarios. The linear trends of LAI and carbon flux show an obvious continuous increase from historical climatic period (1971-2000) to the first two climatic periods (2011-2040; 2041-2700) of RCP4.5, then the trends decrease in the third climatic period (2071-2100) of RCP4.5. The cumulative multi model ensemble (MME) net biome production (NBP) is 0.32 kgCm^-2yr^-1 during 1850 to 2005 and 1.43 kgCm^-2yr^-1 during 2006 to 2100, the Tibetan Plateau is a carbon sink during the historical scenario, and TP will uptake more carbon from atmosphere during 2006 to 2100 than 1850 to 2005 under RCP4.5 scenario. LAI, GPP, NPP, Ra and Rh appear more related to the Tas than Pr and Rsds, and the Tas is the primary climatic driver for the plant growth and carbon cycle. With the climate change in twenty-first century under RCP4.5 scenario, Tas still is the primary climate driver for the plant growth and carbon cycle, but the effect of temperature on plant growth and carbon cycle gets weaker.