中文摘要：

全球变暖是国际社会广泛关注的问题。由于以人类目前的认识水平。尚无法完全了解气候变化的内在规律，因此目前对气候变暖认识的确定性与不确定性并存。本文旨在归纳总结目前对全球变暖的认识哪些是确定的，哪些是不确定的。并提出相关建议。气候系统涵盖很多方面，本文重点关注与人类活动造成的气候变暖相关的七个问题。①对全球变暖的认识：近百年全球气候确实在变暖，但为什么又出现了停滞？②对大气中温室气体浓度上升的认识：工业革命以来大气温室气体浓度快速升高是确定的。但未来如何变化有不确定性：（3）对温室气体排放与气温升高的关系（气候敏感度）的认识：在现代大气CO2浓度加倍会导致全球平均增温约3．0气，但是在更长时间尺度上气候敏感度是不确定的；④对于气候模式的认识：它能够很好地模拟出近百年的气候变暖趋势，且证明人类活动可能是现代气候变暖的主要原因．但模式不能充分描述地球系统的变化，只能表征地球系统的部分特征；⑤对于气候预估的认识：根据排放情景预估本世纪气候继续变暖，但还将变暖多少不确定；⑥对于2℃阈值的认识：它是人类控制升温的一个设想。作为应对气候变化的约束性目标，但是升温幅度何时达到2℃不确定；⑦对于地球系统临界点的认识：地球系统已有一些危险的信号。但何时达到临界点不确定。在适应和减缓全球变暖、调整产业结构等应对行动中，应全面、综合考虑气候变化认识的确定性与不确定性，应对确定性的变化，规避不确定性的风险。

英文摘要：

Global warming has been greatly concerned by the whole world. Due to the limitation we have currently it is still difficult to fully understand the mechanism and physical science of climate change. Now both certainty and uncertainty coexist in the climate warming understanding. This paper aims to summarise certainties and uncertainties in climate wanning studies, which focus on seven key problems related to human activities. The seven problems include （1） Climate warming： the global climate has indeed been warming in the past century, but the warming pauses now. （2） Atmospheric concentrations of the greenhouse gases ： the rapid increase since the Industrial Revolution is certain, whereas future variation in atmospheric greenhouse gas concentrations is uncertain.（3） Relationship between greenhouse gas emissions and climate warming （ climate sensitivity） ： the doubling of CO2 concentrations in the modern atmosphere will result in an average global warming of approximately 3.0 ℃, but climate sensitivity on a longer time scale is uncertain. （4） Climate models： they can predict climate wanning trends based on data from the last 100 years, and this demonstrates that human activity may be the main cause of modern climatic warming, but they only represent some of the features of earth＇ s climate system. （5） Future climate change： based on the assumptive emissions scenarios, we can predict that the global climate will continue to warm in this century, but it is uncertain to what degree that warming will continue. （6） 2 ℃ wanning threshold： this threshold is a goal envisioned by humans who want to control warming, but it is uncertain as when the magnitude of warming will reach 2 ℃. （7） A tipping point in the earth system ： earth＇ s systems already show some dangerous signals of change, but it is uncertain as to when a tipping point will be reached. Therefore, we should comprehensively take into account the level of certainty and uncertainty in our understanding of cli