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Terrestrial Carbon Cycle Dynamics in CMIP5 Last Glacial Maximum and mid-Holocene climate simulations

CMIP5末次盛冰期和全新世中期气候模拟中的陆地碳循环动力学

基本信息

批准号：
NE/J005274/1
负责人：
Joy Singarayer
金额：
$ 11.64万
依托单位：
University of Bristol
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2011
资助国家：
英国
起止时间：
2011 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FJ005274%2F1
关键词：
Terrestrial Carbon Cycle Dynamics CMIP5

项目摘要

1. ContextNew state-of-the-art global climate models are currently running the next generation of future climate change predictions, which will be incorporated into the fifth release of the Intergovernmental Panel on Climate Change (IPCC) assessment report. These models are more sophisticated than before and most include a wide range of biogeochemical processes for the first time (e.g. interactive vegetation, carbon cycle dynamics, atmospheric dust). These model simulations provide great opportunities to advance scientific understanding of Earth system feedbacks and provide more robust projections for future impacts of anthropogenic greenhouse gas emissions. In order to develop this understanding inter-model comparison is essential to elucidate the processes that cause model discrepancies and how they influence predictions of climate change. Climate models which show broad agreement when modelling present day climate can differ considerably in their estimates of future changes. Modelling past climates such as the Last Glacial Maximum (LGM; 21,000 years ago) provide the opportunity to test the ability of those same models to recreate climates very different to today, and thereby offer greater potential to evaluate important Earth system feedback processes and how they contribute to future projections than by using modern-day validation alone. In particular, the effect of climate feedbacks through biogeochemical processes, such as the carbon cycle, has been highlighted by CMIP5 (Coupled Model Intercomparison Project) and the IPCC AR4 as a key scientific issue. For understanding feedbacks through the carbon cycle, past climates again are vital to enable to study the Earth system in a state that is unperturbed by human emissions. 2. Aims and objectivesThe main aim of this study is to use the simulations of two particular past time periods to test the ability of state-of-the-art climate models that being used for future climate projections to reproduce very different climates. The first time period is the mid-Holocene (6,000 years ago), when summer insolation in the northern hemisphere was larger than today, causing intensification of monsoon systems. Feedbacks between the hydrological cycle and the terrestrial biosphere resulted in large-scale vegetation in the Sahara, known as the 'Green Sahara'. There is good evidence about the extent of Sahara vegetation during the mid-Holocene, and it provides a strong feature to test in the climate model simulations. The second time period is the LGM, when large ice-sheets covered much of the northern hemisphere, carbon dioxide levels in the atmosphere were lower (180 ppm) and global temperatures were reduced by several degrees. One of the major questions from this time period is how changes in terrestrial carbon reservoirs and climate-carbon feedbacks contributed to the low atmospheric carbon dioxide levels. We aim to quantify changes in global terrestrial carbon storage and by quantifying and evaluating these natural processes this will help to constrain climate-carbon cycle feedbacks in future climate change projections.3. Potential applications and benefitsThis study will directly address evaluate realistic current climate models are and address the question of how natural carbon-climate feedbacks influence changing climates. They will thereby improve our understanding of the factors which are important for future projections of climate. The results of our analyses will contribute to the fifth assessment report of the IPCC. Ultimately, they will inform global and UK policy on allowable carbon emissions. In addition, scientists from a wide spectrum of research fields are likely to be interested in the results of this project. These disciplines include palaeoclimate and palaeoenvironmental research, Earth system modelling, palaeontology, biogeochemistry, and future climate change research.

1.新的最先进的全球气候模型目前正在运行下一代未来气候变化预测，这些预测将纳入政府间气候变化专门委员会（IPCC）评估报告的第五版。这些模型比以前更加复杂，大多数首次包括了广泛的地球化学过程（例如相互作用的植被、碳循环动力学、大气尘埃）。这些模型模拟为促进对地球系统反馈的科学理解提供了很好的机会，并为人为温室气体排放的未来影响提供了更有力的预测。为了加深这种理解，模型间比较对于阐明导致模型差异的过程以及它们如何影响气候变化的预测至关重要。在模拟当今气候时表现出广泛一致性的气候模型在对未来变化的估计中可能会有很大的不同。模拟过去的气候，如末次盛冰期（LGM; 21，000年前）提供了测试这些相同模型重现与今天截然不同的气候的能力的机会，从而提供了更大的潜力来评估重要的地球系统反馈过程以及它们如何有助于未来的预测，而不是仅仅使用现代验证。特别是，CMIP 5（耦合模式相互比较项目）和气专委第四次评估报告强调，通过碳循环等地球化学过程的气候反馈效应是一个关键的科学问题。为了了解碳循环的反馈，过去的气候对于研究不受人类排放干扰的地球系统至关重要。2.本研究的主要目的是使用过去两个特定时间段的模拟来测试用于未来气候预测的最先进的气候模型再现非常不同的气候的能力。第一个时期是全新世中期（6,000年前），当时北方半球的夏季日照比今天大，导致季风系统增强。水文循环和陆地生物圈之间的反馈导致了撒哈拉大规模的植被，被称为“绿色撒哈拉”。有很好的证据表明撒哈拉植被在全新世中期的范围，它提供了一个强大的功能，在气候模型模拟测试。第二个时期是LGM，当时大冰盖覆盖了北方的大部分地区，大气中的二氧化碳水平较低（180 ppm），全球气温降低了几度。这一时期的主要问题之一是陆地碳库和气候碳反馈的变化如何导致大气二氧化碳水平较低。我们的目标是量化全球陆地碳储量的变化，通过量化和评估这些自然过程，这将有助于在未来的气候变化预测中限制气候-碳循环反馈。潜在的应用和效益这项研究将直接解决评估现实的当前气候模型是和解决自然碳气候反馈如何影响气候变化的问题。因此，它们将提高我们对未来气候预测的重要因素的理解。我们的分析结果将有助于IPCC第五次评估报告。最终，它们将为全球和英国关于允许碳排放的政策提供信息。此外，来自广泛研究领域的科学家可能对该项目的结果感兴趣。这些学科包括古气候和古环境研究、地球系统建模、古生物学、地球化学和未来气候变化研究。