古气候演化特征、驱动与反馈及对现代气候变化研究的启示意义

CHARACTERISTICS,DRIVERS AND FEEDBACKS OF PALEO-CLIMATIC VARIATIONS AND THE IMPLICATIONS FOR MODERN CLIMATE CHANGE RESEARCH

古气候与现代气候变化研究如何有效结合,特别是古气候研究如何为理解现代气候变化过程提供背景条件、边界约束和理论框架,值得深入探讨。文章以现代、历史时期、全新世、晚第四纪和新生代为时间基线,回顾阐述了过去气候演变特征、成因机制及其对现代气候变化研究的启示意义,探讨了过去与现代气候变化融合研究中存在的不确定性。过去气候演化过程的研究,加深了人们对地球气候系统运行机制的理解。研究表明,各个时期中,地球气候经历了不同相位、幅度和速率的变化,气候系统各分量之间发生了复杂的相互作用,以地表温度为代表的地球表面热力环境演化是各不同阶段气候变化的基本表现形式。全球温度变化不仅受到太阳输出辐射、地球轨道参数和地球构造运动等的影响,而且与地球表层水圈中的海洋、冰冻圈中的大陆冰盖、生物圈中的海洋浮游生物和陆地植被,以及大气圈中的温室气体、粉尘气溶胶、水汽和云等活跃组分之间,存在着多尺度复杂反馈作用。在同一时间尺度上,气候系统分量的互馈通路可能是同向的、可比的,各分量之间的对应关系或具有一致性,研究结论对于预估未来气候变化有借鉴意义;但在不同时间尺度上,气候系统各分量之间的相互联系机制可能难有一致性和可比性,古今互鉴,就需要慎重。

How to reconcile the studies of paleo-climatology and modern climate change,and,in particular,how the studies of paleo-climatology contribute to the understanding of modern climate change,are worth thinking about.This review,which is completed based on the keynote speech of the academic forum on"Scales,drivers and feedbacks of climate system change:building bridge between paleoclimate and modern climate"held in Yinchuan,China,in August 2018,makes an attempt to summarize the latest research and thoughts in blending paleoclimatology and global climate change.Starting from the various timescales in the periods of the modern time,history,Holocene,Late Quaternary and Cenozoic,we discuss the facts,causes and mechanisms of the past climate change and variability,and their significances to modern climate change research,and also evaluates the uncertainty in the interdisciplinary study of paleo-climate and modern climate.We conclude that variations of various magnitudes and rates in earth climate occurred in the past,accompanied by the complex interactions among the various components of climate system.The global surface temperature was controlled not merely by the emitted solar radiation,the earth orbital parameters and the earth tectonic movement,but also by the complex interactions and feedbacks among the oceans of the hydrosphere,the ice sheets and snow cover of the cryosphere,the oceanic plankton and terrestrial vegetation of the biosphere,and the active constituents(such as CO2,dust aerosols,moisture and clouds)of the atmosphere.Under the same timescale and boundary condition,the interactions and feedbacks of the components may be similar in mechanism with the comparability of variability between any two variables;under the different timescales or the varied boundary conditions,however,the correspondence of the variabilities between any two components can hardly be found,and caution has to be taken when discussing the role paleoclimatology in understanding modern climate change.We hope that this review can provide some reference for in-depth research of the relative issues in the future.