从全球到区域气候变化

尽管气候变化是全球性的现象,但其表现和结果随区域不同而不同,因此区域气候信息对于气候变化的作用和风险评估很重要。基于此,IPCC第六次评估报告（AR6）第一工作组（WGI）报告第十章对如何从全球链接到区域气候变化方面进行了评估。区域气候变化是对自然强迫和人类活动的区域响应、对大尺度气候系统内部变率的响应和区域气候本身反馈过程的相互作用结果。因此,本章重点关注如何从多套观测资料,不同模式的集合,物理过程的理解、专家判断和本地信息等多元信息中有效提炼出区域信息的方法。通过提炼方法指出人类活动是许多次大陆尺度上1950年代以来区域平均温度变化的主要驱动力,但参考时段和阈值的选择对人类活动信号是否出现和出现的早晚有影响。人类活动对一些区域的多年代际降水变化有一定贡献,但其不确定性相对全球平均而言更大。气候系统内部变率可以在很大程度上延迟和阻碍人类活动信号在区域气候变化中的出现。区域气候变化的评估给决策者提供了更多有用的信息,增加了评估报告的适用性。

Linking global to regional climate change

Although climate change is a global phenomenon, its manifestations and consequences are different in different regions, and therefore climate information on spatial scales ranging from sub-continental to local is important for the impact and risk assessments of climate change. To respond to this, the WGI report of IPCC AR6 Chapter 10 assess how to link the global to regional climate change. Regional climate change is the result of the interplay between regional responses to both natural forcings and human influence, responses to large-scale climate phenomena characterizing internal variability, and processes and feedbacks of a regional nature. This chapter emphasized how to distill regional climate information from multiple observational datasets, ensembles of different model types, process understanding, expert judgement and indigenous knowledge. The distillation attribute multi-decadal regional trends to the interplay between external forcing and internal variability. Human influence has been a major driver of regional mean temperature change since 1950 in many sub-continental regions of the world. The choice of the reference period and signal-to-noise threshold is important to robustly assess the future emergence of anthropogenic signals, as well as past emergence results. Human influence has contributed to multi-decadal mean precipitation changes in several regions, internal variability can delay emergence of the anthropogenic signal in long-term precipitation changes in many land regions. Distilling regional climate information from multiple lines of evidence will increase the fitness usefulness and relevance for decision-making.