Greenhouse gas emissions drive global dryland expansion but not spatial patterns of change in aridification
Greenhouse gas emissions drive global dryland expansion but not spatial patterns of change in aridification
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温室气体排放推动全球旱地扩张，但并未推动干旱化的空间格局变化
DOI：
10.1175/jcli-d-22-0103.1
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发表时间：
2022
影响因子：
4.9
通讯作者：
Dongdong Kong
中科院分区：
文献类型：
--
作者：
Shuyun Feng;Xihui Gu;Sijia Luo;Ruihan Liu;Aminjon Gulakhmadov;Louise J. Slater;Jianfeng Li;Xiang Zhang;Dongdong Kong
旱地在地球环境和人类系统中发挥着重要作用。尽管以前的研究对旱地扩张进行了广泛的研究，但缺乏支持人类引起的旱地范围变化的定量证据。在这里，我们使用耦合模型比较项目第六阶段的多个观测数据集和模型模拟，采用基于相关性和最优指纹识别方法来进行旱地扩张的定量检测和归因。我们的结果表明，1990-2014年近期和1950-74年过去一段时期大气干旱度（即由降水量与潜在蒸散量之比定义的干旱指数）的空间变化不太可能是由温室气体（GHG）排放引起的。然而，全球范围内的旱地扩张很可能（至少 95% 的置信水平）主要是由温室气体排放驱动的。根据观测，1950年至2014年期间，全球旱地面积扩大了3.67%，而温室气体排放导致的旱地面积估计约为4.5%。在中排放和高排放情景下，旱地预计将继续扩大，其人口将增加，直到全球变暖达到比工业化前温度高约 3.5°C。如果变暖超过~3.5°C，人口密度的减少将导致旱地人口的减少。我们的研究结果首次为温室气体排放对全球旱地扩张的主导影响提供了定量证据，这有助于旱地适应人为气候变化。 意义陈述在过去的几十年里，据报道，全球旱地显示出基于大气干旱度（即由降水量与潜在蒸散量之比定义的干旱指数）的空间和时间变化。使用两种检测和归因方法，1990-2014年和1950-74年间大气干旱的空间变化模式不太可能是由温室气体（GHG）排放驱动的，而全球旱地的时间扩张（即1950年至2014年期间的3.67%）主要归因于温室气体排放（贡献率：~122%）。检测和归因分析的定量证据支持温室气体排放在全球旱地扩张中的主导作用，除非采取气候适应措施，否则在未来变暖的情况下，将增加遭受水资源短缺的人口。
Drylands play an essential role in Earth’s environment and human systems. Although dryland expansion has been widely investigated in previous studies, there is a lack of quantitative evidence supporting human-induced changes in dryland extent. Here, using multiple observational datasets and model simulations from phase 6 of the Coupled Model Intercomparison Project, we employ both correlation-based and optimal fingerprinting approaches to conduct quantitative detection and attribution of dryland expansion. Our results show that spatial changes in atmospheric aridity (i.e., the aridity index defined by the ratio of precipitation to potential evapotranspiration) between the recent period 1990–2014 and the past period 1950–74 are unlikely to have been caused by greenhouse gas (GHG) emissions. However, it is very likely (at least 95% confidence level) that dryland expansion at the global scale was driven principally by GHG emissions. Over the period 1950–2014, global drylands expanded by 3.67% according to observations, and the dryland expansion attributed to GHG emissions is estimated as ∼4.5%. Drylands are projected to continue expanding, and their populations to increase until global warming reaches ∼3.5°C above preindustrial temperature under the middle- and high-emission scenarios. If warming exceeds ∼3.5°C, a reduction in population density would drive a decrease in dryland population. Our results for the first time provide quantitative evidence for the dominant effects of GHG emissions on global dryland expansion, which is helpful for anthropogenic climate change adaptation in drylands.Significance StatementIn the past decades, global drylands have been reported to show changes in space and time, based on atmospheric aridity (i.e., aridity index defined by the ratio of precipitation to potential evapotranspiration). Using two detection and attribution methods, the spatial change patterns of atmospheric aridity between 1990–2014 and 1950–74 are unlikely to be driven by greenhouse gas (GHG) emissions, whereas the temporal expansion of global drylands (i.e., 3.67% from 1950 to 2014) is principally attributed to GHG emissions (contribution: ∼122%). Quantitative evidence from the detection and attribution analysis supports the dominant role of greenhouse gas emissions in global dryland expansion, which will increase the population suffering from water shortages under future warming unless climate adaptation is adopted.