Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany.
College of Engineering, Mathematics &Physical Sciences, University of Exeter, Exeter EX4 4QE, UK.
Nature. 2016 Oct 27;538(7626):499-501. doi: 10.1038/nature19772. Epub 2016 Sep 28.
Uncertainties in the response of vegetation to rising atmospheric CO concentrations contribute to the large spread in projections of future climate change. Climate-carbon cycle models generally agree that elevated atmospheric CO concentrations will enhance terrestrial gross primary productivity (GPP). However, the magnitude of this CO fertilization effect varies from a 20 per cent to a 60 per cent increase in GPP for a doubling of atmospheric CO concentrations in model studies. Here we demonstrate emergent constraints on large-scale CO fertilization using observed changes in the amplitude of the atmospheric CO seasonal cycle that are thought to be the result of increasing terrestrial GPP. Our comparison of atmospheric CO measurements from Point Barrow in Alaska and Cape Kumukahi in Hawaii with historical simulations of the latest climate-carbon cycle models demonstrates that the increase in the amplitude of the CO seasonal cycle at both measurement sites is consistent with increasing annual mean GPP, driven in part by climate warming, but with differences in CO fertilization controlling the spread among the model trends. As a result, the relationship between the amplitude of the CO seasonal cycle and the magnitude of CO fertilization of GPP is almost linear across the entire ensemble of models. When combined with the observed trends in the seasonal CO amplitude, these relationships lead to consistent emergent constraints on the CO fertilization of GPP. Overall, we estimate a GPP increase of 37 ± 9 per cent for high-latitude ecosystems and 32 ± 9 per cent for extratropical ecosystems under a doubling of atmospheric CO concentrations on the basis of the Point Barrow and Cape Kumukahi records, respectively.
植被对大气 CO 浓度升高的响应存在不确定性，这导致未来气候变化预测存在较大差异。气候-碳循环模型普遍认为，大气 CO 浓度升高将增强陆地总初级生产力（GPP）。然而，在模型研究中，大气 CO 浓度加倍时，这种 CO 施肥效应的幅度从 GPP 增加 20%到 60%不等。在这里，我们利用大气 CO 季节性循环幅度的观测变化来证明大规模 CO 施肥的新兴限制，这些变化被认为是陆地 GPP 增加的结果。我们将阿拉斯加巴罗角和夏威夷库马卡希角的大气 CO 测量结果与最新气候-碳循环模型的历史模拟进行了比较，结果表明，两个测量点的 CO 季节性循环幅度的增加与年平均 GPP 的增加一致，部分原因是气候变暖，但 CO 施肥的差异控制着模型趋势的差异。因此，在整个模型集合中，CO 季节性循环幅度与 GPP 的 CO 施肥量之间的关系几乎是线性的。当结合 CO 季节性幅度的观测趋势时，这些关系导致对 GPP 的 CO 施肥的一致新兴限制。总的来说，根据巴罗角和库马卡希角的记录，我们估计在大气 CO 浓度加倍的情况下，高纬度生态系统的 GPP 将增加 37±9%，而亚热带生态系统的 GPP 将增加 32±9%。
