Department of Geography, University of Cambridge, Cambridge CB2 3EN, United Kingdom.
Proc Natl Acad Sci U S A. 2014 Mar 4;111(9):3280-5. doi: 10.1073/pnas.1222477110. Epub 2013 Dec 16.
Future climate change and increasing atmospheric CO2 are expected to cause major changes in vegetation structure and function over large fractions of the global land surface. Seven global vegetation models are used to analyze possible responses to future climate simulated by a range of general circulation models run under all four representative concentration pathway scenarios of changing concentrations of greenhouse gases. All 110 simulations predict an increase in global vegetation carbon to 2100, but with substantial variation between vegetation models. For example, at 4 °C of global land surface warming (510-758 ppm of CO2), vegetation carbon increases by 52-477 Pg C (224 Pg C mean), mainly due to CO2 fertilization of photosynthesis. Simulations agree on large regional increases across much of the boreal forest, western Amazonia, central Africa, western China, and southeast Asia, with reductions across southwestern North America, central South America, southern Mediterranean areas, southwestern Africa, and southwestern Australia. Four vegetation models display discontinuities across 4 °C of warming, indicating global thresholds in the balance of positive and negative influences on productivity and biomass. In contrast to previous global vegetation model studies, we emphasize the importance of uncertainties in projected changes in carbon residence times. We find, when all seven models are considered for one representative concentration pathway × general circulation model combination, such uncertainties explain 30% more variation in modeled vegetation carbon change than responses of net primary productivity alone, increasing to 151% for non-HYBRID4 models. A change in research priorities away from production and toward structural dynamics and demographic processes is recommended.
未来的气候变化和大气中二氧化碳浓度的增加预计将导致大部分全球陆地表面的植被结构和功能发生重大变化。我们使用七种全球植被模型来分析在四种温室气体浓度变化的代表性浓度途径情景下，由一系列通用环流模型模拟的未来气候下可能出现的响应。所有 110 次模拟预测到 2100 年全球植被碳将增加，但不同植被模型之间存在很大差异。例如，在全球陆地表面变暖 4°C（CO2 浓度为 510-758ppm）的情况下，植被碳增加 52-477PgC（平均 224PgC），主要是由于光合作用的 CO2 施肥作用。模拟结果一致认为，在北方森林、西部亚马孙地区、中非、中国西部和东南亚的大部分地区，以及在北美西南部、南美中部、地中海南部地区、非洲西南部和澳大利亚西南部，将出现大面积的区域增加，而在这些地区的减少。四个植被模型在变暖 4°C 时显示出不连续，表明在生产力和生物量的积极和消极影响之间存在全球平衡的阈值。与以前的全球植被模型研究不同，我们强调了对碳居留时间预计变化的不确定性的重视。我们发现，当考虑到一个代表性浓度途径与一个通用环流模型组合的七个模型时，这种不确定性解释了模型中植被碳变化的 30%以上的差异，而非 HYBRID4 模型的差异增加到 151%。建议将研究重点从生产转向结构动态和人口过程。
