刘晓东1,3
1. 中国科学院地球环境研究所, 黄土与第四纪地质国家重点实验室, 陕西 西安 710061
2. 中国科学院青藏高原地球科学卓越创新中心, 北京 100101
3. 中国科学院大学, 北京 100049
基金项目: 国家自然科学基金项目（批准号：41991254和41690115）和中国科学院（B类）战略性先导科技专项项目（批准号：XDB26000000）共同资助
详细信息
作者简介: 李新周, 男, 42岁, 高级工程师, 古气候模拟研究, E-mail:lixz@ieecas.cn
中图分类号: P532;P534.63+2 收稿日期:2020-06-05
修回日期:2020-08-29
刊出日期:2020-11-30
A comparative study of climate change in East Asia during the Early Holocene and 10000 years after present: Roles of natural forcing and human activities
Li Xinzhou1,2,,Liu Xiaodong1,3
1. State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, Shaanxi
2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101
3. University of Chinese Academy of Sciences, Beijing 100049
MSC: P532;P534.63+2
--> Received Date: 05 June 2020
Revised Date: 29 August 2020
Publish Date: 30 November 2020
摘要
摘要:以准两万年周期为特征的地球岁差参数变化所引起的太阳辐射变动是造成万年尺度亚洲季风气候变化的主要驱动力。现代地球近日点时间出现在冬季12月份，但在约1万年（10 ka）前的早全新世和未来10 ka后的未来，近日点时间均出现在夏季6月份，因而对北半球气候施以最强的岁差强迫。未来10 ka后气候除了受轨道改变引起太阳辐射变化强迫外，主要受人类活动排放温室气体影响。文章利用一个全球气候模式完成了早全新世、未来10 ka和现代（包括工业革命前）这3个时间段的一系列敏感性试验，对比检查了自然强迫和人类活动对东亚区域气候的可能影响。模拟结果表明：在仅有自然强迫时，与工业革命前相比，岁差引起的太阳辐射变化可造成早全新世及未来10 ka后东亚区域夏季变暖，冬季变冷，东亚夏季风和冬季风均显著增强。早全新世东亚区域夏季降水也明显增加，但因自然强迫下未来10 ka后温室气体浓度偏低，导致夏季降水出现减少现象。未来人类活动带来的温室气体浓度增加将引起地表温度显著增温，使东亚夏季风增强而冬季风减弱。在同时考虑自然强迫和人类活动影响后，东亚夏季降水进一步增加，未来10 ka后东亚夏季降水将较工业革命前增加9.87%，而早全新世只增加了2.66%。同时，在自然和人类共同作用下10 ka后东亚冬季风将减弱，而在仅有自然强迫的早全新世东亚冬季风却是增强的。这一研究说明，虽然未来10 ka后是岁差强迫最强盛时期，但人类活动可能会扰乱岁差尺度上东亚区域气候的自然演变规律，在未来气候预估中必须综合考虑自然强迫和人为因子共同影响。
关键词: 人类活动/
自然强迫/
岁差尺度/
东亚季风区
Abstract:It is generally accepted within the scientific community that within the glacial-interglacial cycles of the Quaternary, over 100 ka cycles, the colder glacial period generally lasts 70 ka to 90 ka. In contrast, the relatively warm interglacial period between two glacial periods usually lasts 10 ka to 30 ka. The Last Glacial Maximum appeared at approximately 21 ka before present(B.P.), after which the Earth's climate entered the deglacial period and Holocene. From the pattern of the glacial-interglacial cycle, it is clear that the Earth's climate is currently entering or should soon enter the next glacial period. However, observations and numerical simulations in recent decades have confirmed that human-induced dramatic increases in the concentrations of greenhouse gases in the atmosphere since the Industrial Revolution is the dominant driver of global warming. The Earth's climate system may be undergoing a process of transition from a system subject to a single natural forcing to a system subject to both natural and human-related drivers. Human-related drivers may even have a more significant effect on the global climate compared to natural factors, and this effect will continue for a long time. The effects of polar ice sheets on the global climate have gradually diminished since the Early Holocene, and variations in solar radiation resulting from variations in the Earth's precession parameters characterized by a quasi ca.20 ka cycle is the main driving force of the changes to the Asian monsoon on a 10 ka time scale. Although the Earth's perihelion currently falls in December, during the Early Holocene and by 10 ka after present, the perihelion is in June, representing the strongest precession forcing on the climate of the Northern Hemisphere. Over the next 10 ka, it is generally accepted that emissions of greenhouse gases from human activities in combination with a change in solar radiation resulting from the Earth's orbital forcing will be the main drivers of the global climate. Under natural conditions, changes in atmospheric greenhouse gas concentrations would follow the pattern of the glacial-interglacial cycle; however, human activities have resulted in elevated atmospheric greenhouse gas concentrations that far exceed the range of natural changes. The United Nations Intergovernmental Panel on Climate Change(IPCC) Fifth Assessment Report(AR5) points out that at current concentrations, even if greenhouse gases emissions were to be constrained to fall within the medium representative concentration pathway(RCP4.5), atmospheric CO2 concentrations would reach 543 ppm by 2100.
The current study used the global climate model CESM 1.2 to complete five sensitivity experiments:(1) The Early Holocene(EH); (2) Pre-Industrial Revolution(PI); (3) Present-day(PD); (4) Future under the natural forcing only(FN); (5) Future with natural and anthropogenic impacts(FA). The current study compared and analyzed the possible impacts of changes in solar radiation and greenhouse gases resulting from both natural processes and human activities on the climate of East Asia. The simulation results showed that changes in solar radiation resulting from changes caused by precession could lead to an increase and decrease in the surface temperature of the East Asian region in summer and winter, respectively, during in the EH and FN relative to that in the PI. Besides, the simulation showed significant enhancement of the winter and summer monsoons and that summer precipitation in East Asia during the EH is significantly increased. However, low concentrations of greenhouse gases resulting from natural forcing in FN will result in a decrease in summer precipitation. The increase in greenhouse gas concentration resulting from human activities will result in a significant increase in surface temperature, which will strengthen and weaken the East Asian summer and winter monsoons, respectively. A combination of climate forcing from natural processes and human activities will result in an increase in summer precipitation in East Asia by 9.87% in the FA relative to the PI levels, but only by 2.66% in the EH. At the same time, under the joint climate forcing by natural processes and human activities, the East Asian winter monsoon will weaken during the FA, whereas the East Asian winter monsoon under only natural forcing will be strengthened in the early Holocene. This result suggests that human activities may disturb the natural evolution of the climate of East Asia on the precession scale, even during the period of maximum precession forcing.
Key words:human activities/
natural forcing/
precession scale/
East Asian monsoon
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