Future Changes in Global Terrestrial Carbon Cycle under RCP Scenarios

Terrestrial ecosystem plays the important role as carbon sink in the global carbon cycle. Understanding of interactions of terrestrial carbon cycle with climate is important for better prediction of future climate change. In this paper, terrestrial carbon cycle is investigated by Hadley Centre Global Environmental Model, version 2, Carbon Cycle (HadGEM2-CC) that considers vegetation dynamics and an interactive carbon cycle with climate. The simulation for future projection is based on the three (8.5/4.5/2.6) representative concentration pathways (RCPs) from 2006 to 2100 and compared with historical land carbon uptake from 1979 to 2005. Projected changes in ecological features such as production, respiration, net ecosystem exchange and climate condition show similar pattern in three RCPs, while the response amplitude in each RCPs are different. For all RCP scenarios, temperature and precipitation increase with rising of the atmospheric CO2. Such climate conditions are favorable for vegetation growth and extension, causing future increase of terrestrial carbon uptakes in all RCPs. At the end of 21st century, the global average of gross and net primary productions and respiration increase in all RCPs and terrestrial ecosystem remains as carbon sink. This enhancement of land CO2 uptake is attributed by the vegetated area expansion, increasing LAI, and early onset of growing season. After mid-21st century, temperature rising leads to excessive increase of soil respiration than net primary production and thus the terrestrial carbon uptake begins to fall since that time. Regionally the NEE average value of East-Asia (90 degrees E-140 degrees E, 20 degrees N similar to 60 degrees N) area is bigger than that of the same latitude band. In the end-21 st the NEE mean values in East-Asia area are -2.09 PgC yr(-1), -1.12 PgC yr(-1), -0.47 PgC yr(-1) and zonal mean NEEs of the same latitude region are -1.12 PgC yr(-1), -0.55 PgC yr(-1), -0.17 PgC yr(-1) for RCP 8.5, 4.5, 2.6.