气候变化领域集成服务门户

A multi- model- based assessment is made to assess the trends and variability in the land carbon uptake in India during the period 1901- 2010. Data from nine models, used in a recent land surface model inter- comparison project called TRENDY, are used for this purpose. Our analysis is focused on the trends and variability in the net primary productivity ( NPP), net ecosystem productivity ( NEP) and net ecosystem exchange ( NEE). The multi- model mean NPP shows a positive trend of 2.03% per decade during this period. The NEP, which is the difference between NPP and heterotrophic respiration, has a mean value of - 0.138 +/- 0.086 PgCyr - 1 over this region. According to our analysis of TRENDY multimodels, the inter- annual variation in NPP and NEP is strongly driven by precipitation, but remote drivers such as El Ni no Southern Oscillation ( ENSO) and Indian Ocean Dipole ( IOD) do not have a strong influence. The water use efficiency ( WUE) shows an increase of about 25% over the 110- yr period. Our multi- model- based estimate of the cumulative NEE is 0.613 +/- 0.1PgC during 1901- 2010, indicating that the Indian terrestrial ecosystem was neither a strong source nor a significant sink during this period. However, we caution that our conclusion is based on a limited set of offline land models, and the results presented here have large uncertainties due to model resolution and parameterisation of various land surface processes, the inadequate validation procedures and the use of limited number of models and land use change data sets. Further investigations using more observational data, rigorous validation using extensive observational data sets and a set of comprehensive coupled models that include several feedbacks between land, atmosphere, ocean and the cryosphere are needed to assess the robustness of our results.