Lei Zhu1,2, Philippe Ciais3, Ana Bastos4,5, Ashley P Ballantyne3,6, Frederic Chevallier3, Thomas Gasser7, Masayuki Kondo8,9, Julia Pongratz4,10, Christian Rödenbeck11, Wei Li12,13. 1. Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing, China. 2. Joint Center for Global Change Studies, Beijing, China. 3. Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France. 4. Department of Geography, Ludwig-Maximilians Universität, München, Germany. 5. Department of Biogeochemical Integration, Max Planck Institute for Biogeochemistry, Jena, Germany. 6. Department of Ecosystem and Conservation Sciences, WA Franke College of Forestry and Conservation, University of Montana, Missoula, MT, USA. 7. International Institute for Applied Systems Analysis (IIASA), Laxenburg, Austria. 8. Institute for Space-Earth Environmental Research, Nagoya University, Nagoya, Japan. 9. Center for Global Environmental Research, National Institute for Environmental Studies, Tsukuba, Japan. 10. Max Planck Institute for Meteorology, Hamburg, Germany. 11. Department of Biogeochmical Systems, Max Planck Institute for Biogeochemistry, Jena, Germany. 12. Ministry of Education Key Laboratory for Earth System Modeling, Department of Earth System Science, Tsinghua University, Beijing, China. wli2019@tsinghua.edu.cn. 13. Joint Center for Global Change Studies, Beijing, China. wli2019@tsinghua.edu.cn.
Abstract
BACKGROUND: The climate mitigation target of limiting the temperature increase below 2 °C above the pre-industrial levels requires the efforts from all countries. Tracking the trajectory of the land carbon sink efficiency is thus crucial to evaluate the nationally determined contributions (NDCs). Here, we define the instantaneous land sink efficiency as the ratio of natural land carbon sinks to emissions from fossil fuel and land-use and land-cover change with a value of 1 indicating carbon neutrality to track its temporal dynamics in the past decades. RESULTS: Land sink efficiency has been decreasing during 1957-1990 because of the increased emissions from fossil fuel. After the effect of the Mt. Pinatubo eruption diminished (after 1994), the land sink efficiency firstly increased before 2009 and then began to decrease again after 2009. This reversal around 2009 is mostly attributed to changes in land sinks in tropical regions in response to climate variations. CONCLUSIONS: The decreasing trend of land sink efficiency in recent years reveals greater challenges in climate change mitigation, and that climate impacts on land carbon sinks must be accurately quantified to assess the effectiveness of regional scale climate mitigation policies.
BACKGROUND: The climate mitigation target of limiting the temperature increase below 2 °C above the pre-industrial levels requires the efforts from all countries. Tracking the trajectory of the land carbon sink efficiency is thus crucial to evaluate the nationally determined contributions (NDCs). Here, we define the instantaneous land sink efficiency as the ratio of natural land carbon sinks to emissions from fossil fuel and land-use and land-cover change with a value of 1 indicating carbon neutrality to track its temporal dynamics in the past decades. RESULTS: Land sink efficiency has been decreasing during 1957-1990 because of the increased emissions from fossil fuel. After the effect of the Mt. Pinatubo eruption diminished (after 1994), the land sink efficiency firstly increased before 2009 and then began to decrease again after 2009. This reversal around 2009 is mostly attributed to changes in land sinks in tropical regions in response to climate variations. CONCLUSIONS: The decreasing trend of land sink efficiency in recent years reveals greater challenges in climate change mitigation, and that climate impacts on land carbon sinks must be accurately quantified to assess the effectiveness of regional scale climate mitigation policies.
Entities:
Keywords:
Carbon neutrality; Land carbon sink efficiency; Trend reversal