Articles | Volume 10, issue 1
Biogeosciences, 10, 513–527, 2013

Special issue: REgional Carbon Cycle Assessment and Processes (RECCAP)

Biogeosciences, 10, 513–527, 2013

Research article 25 Jan 2013

Research article | 25 Jan 2013

The carbon budget of South Asia

P. K. Patra1, J. G. Canadell2, R. A. Houghton3, S. L. Piao4, N.-H. Oh5, P. Ciais6, K. R. Manjunath7, A. Chhabra7, T. Wang6, T. Bhattacharya8, P. Bousquet6, J. Hartman9, A. Ito10, E. Mayorga11, Y. Niwa12, P. A. Raymond13, V. V. S. S. Sarma14, and R. Lasco15 P. K. Patra et al.
  • 1Research Institute for Global Change, JAMSTEC, Yokohama 236 0001, Japan
  • 2Global Carbon Project, CSIRO Marine and Atmospheric Research, Canberra, ACT 2601, Australia
  • 3Woods Hole Research Center, 149 Woods Hole Road, Falmouth, MA 02540, USA
  • 4Peeking University, Beijing 100871, China
  • 5Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, South Korea
  • 6IPSL – LSCE, CEA CNRS UVSQ, Centre d'Etudes Orme des Merisiers, 91191 Gif sur Yvette, France
  • 7Space Application Centre, ISRO, Ahmedabad 380 015, India
  • 8National Bureau of Soil Survey and Land use Planning (ICAR) Amravati Road, Nagpur 440 033, India
  • 9Institute for Biogeochemistry and Marine Chemistry, 20146, Hamburg, Germany
  • 10National Institute for Environmental Studies, Tsukuba, Ibaraki 305-8506, Japan
  • 11Applied Physics Laboratory, University of Washington, Seattle, WA 98105, USA
  • 12Meteorological Research Institute, Tsukuba, Japan
  • 13Yale University, New Haven, CT 06511, USA
  • 14National Institute of Oceanography, Visakhapatnam 530 017, India
  • 15The World Agroforestry Centre (ICARF), Laguna 4031, Philippines

Abstract. The source and sinks of carbon dioxide (CO2) and methane (CH4) due to anthropogenic and natural biospheric activities were estimated for the South Asian region (Bangladesh, Bhutan, India, Nepal, Pakistan and Sri Lanka). Flux estimates were based on top-down methods that use inversions of atmospheric data, and bottom-up methods that use field observations, satellite data, and terrestrial ecosystem models. Based on atmospheric CO2 inversions, the net biospheric CO2 flux in South Asia (equivalent to the Net Biome Productivity, NBP) was a sink, estimated at −104 ± 150 Tg C yr−1 during 2007–2008. Based on the bottom-up approach, the net biospheric CO2 flux is estimated to be −191 ± 193 Tg C yr−1 during the period of 2000–2009. This last net flux results from the following flux components: (1) the Net Ecosystem Productivity, NEP (net primary production minus heterotrophic respiration) of −220 ± 186 Tg C yr−1 (2) the annual net carbon flux from land-use change of −14 ± 50 Tg C yr−1, which resulted from a sink of −16 Tg C yr−1 due to the establishment of tree plantations and wood harvest, and a source of 2 Tg C yr−1 due to the expansion of croplands; (3) the riverine export flux from terrestrial ecosystems to the coastal oceans of +42.9 Tg C yr−1; and (4) the net CO2 emission due to biomass burning of +44.1 ± 13.7 Tg C yr−1. Including the emissions from the combustion of fossil fuels of 444 Tg C yr−1 for the 2000s, we estimate a net CO2 land–atmosphere flux of 297 Tg C yr−1. In addition to CO2, a fraction of the sequestered carbon in terrestrial ecosystems is released to the atmosphere as CH4. Based on bottom-up and top-down estimates, and chemistry-transport modeling, we estimate that 37 ± 3.7 Tg C yr−1 were released to atmosphere from South Asia during the 2000s. Taking all CO2 and CH4 fluxes together, our best estimate of the net land–atmosphere CO2-equivalent flux is a net source of 334 Tg C yr−1 for the South Asian region during the 2000s. If CH4 emissions are weighted by radiative forcing of molecular CH4, the total CO2-equivalent flux increases to 1148 Tg C yr−1 suggesting there is great potential of reducing CH4 emissions for stabilizing greenhouse gases concentrations.

Final-revised paper