Schimel David, Stephens Britton B, Fisher Joshua B
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91011; and
Earth Observing Laboratory, National Center for Atmospheric Research, Boulder, CO 80301.
Proc Natl Acad Sci U S A. 2015 Jan 13;112(2):436-41. doi: 10.1073/pnas.1407302112. Epub 2014 Dec 29.
Feedbacks from the terrestrial carbon cycle significantly affect future climate change. The CO2 concentration dependence of global terrestrial carbon storage is one of the largest and most uncertain feedbacks. Theory predicts the CO2 effect should have a tropical maximum, but a large terrestrial sink has been contradicted by analyses of atmospheric CO2 that do not show large tropical uptake. Our results, however, show significant tropical uptake and, combining tropical and extratropical fluxes, suggest that up to 60% of the present-day terrestrial sink is caused by increasing atmospheric CO2. This conclusion is consistent with a validated subset of atmospheric analyses, but uncertainty remains. Improved model diagnostics and new space-based observations can reduce the uncertainty of tropical and temperate zone carbon flux estimates. This analysis supports a significant feedback to future atmospheric CO2 concentrations from carbon uptake in terrestrial ecosystems caused by rising atmospheric CO2 concentrations. This feedback will have substantial tropical contributions, but the magnitude of future carbon uptake by tropical forests also depends on how they respond to climate change and requires their protection from deforestation.
陆地碳循环的反馈对未来气候变化有显著影响。全球陆地碳储量对二氧化碳浓度的依赖性是最大且最不确定的反馈之一。理论预测二氧化碳效应在热带地区最为显著，但大气二氧化碳分析表明热带地区没有大量吸收，这与存在大量陆地碳汇的观点相矛盾。然而，我们的研究结果显示热带地区有显著的碳吸收，结合热带和温带通量来看，表明目前高达60%的陆地碳汇是由大气二氧化碳增加所致。这一结论与经过验证的部分大气分析结果一致，但不确定性仍然存在。改进模型诊断和新的天基观测可以降低热带和温带碳通量估算的不确定性。该分析支持由大气二氧化碳浓度上升导致的陆地生态系统碳吸收对未来大气二氧化碳浓度产生显著反馈这一观点。这种反馈在热带地区贡献巨大，但热带森林未来碳吸收的规模也取决于它们对气候变化的响应方式，并且需要保护它们免受森林砍伐的影响。
