Trends and Variability in Terrestrial Carbon Fluxes and Stocks over India in the 20th and 21st centuries A Multi model Based Assessment

Abstract

Terrestrial ecosystems play an important role in the global carbon cycle by naturally taking up carbon from the atmosphere through photosynthesis and storing this carbon as biomass and soil carbon. There exists a strong, yet complex and uncertain relationship between the terrestrial ecosystems and the climate system. Inadequate knowledge on the regional terrestrial carbon cycle dynamics translates into large uncertainties in the estimation of global terrestrial carbon stocks and fluxes and in turn the climate projections as well. It is important to gain a better understanding of the terrestrial carbon dynamics at a regional level, in order to reduce the uncertainty in the terrestrial carbon estimates at the global scale (LeQuéré et al., 2017, Canadell et al., 2011). The Indian region is very important but relatively unexplored in terms of terrestrial carbon studies. However, significant environmental changes have occurred in the 20th century that has affected the terrestrial carbon dynamics of the Indian region considerably. The present research provides a model based assessment of the trends and variability in terrestrial carbon stocks and fluxes over India. We have used a multi-model based approach to understand the regional dynamics of the carbon cycle in the historical period and to predict the future terrestrial carbon dynamics over India. In the first part of the thesis (Chapter 3), we assess the trends and variability in the land carbon uptake in India during the period 1901-2010 using outputs from nine land surface models that are a part of the TRENDY model inter-comparison project. Outputs from two simulations were used - the S1 simulation where only atmospheric CO2 concentration is varying and the S2 simulation where both the climate and atmospheric CO2 are varying. The simulation S2 represents approximately the actual historical evolution of the system and the S1 simulation is used to make comparisons with S2 to obtain the individual effect of climate change (S2-S1). The changes in S1 simulation wit...