RAPID: Prediction and Predictability for the Multi-decadal Variability in a Changing Climate

这是政府间气候变化专门委员会第五次评估报告（IPCC AR5）中鼓励对气候模式模拟进行诊断分析的致同事信（NSF 11-006）资助的16个快速响应（Rapid）项目之一。在这些项目中进行的研究预计将导致更详细的模式相互比较，更好地理解稳健模式行为，更好地理解和量化未来气候模拟中的不确定性。本项目进行的研究考察了为AR5准备的20世纪气候模拟集合中十年至十年的自然变率。解决的关键问题是1)观测到的全球变暖的哪一部分可以用自然年代际变率来解释？特别是，20世纪中期的变暖在多大程度上是人为引起的，还是自然变率的结果？年代际振荡是如何相互联系的，它们如何调节极端气候事件，如热浪、干旱、洪水和热带气旋？3)这些模式对19世纪末至20世纪的年代际变化的模拟效果如何？这些问题很重要的一个原因是，20世纪的全球平均温度记录包含了显著的年代际波动，而这些波动在多大程度上是自然变率而不是人为活动（例如，气溶胶强迫的变化）的结果尚不清楚。自然的年代际波动将继续叠加在人为变暖上，这些波动可预测的程度是理解和预测平均气候变化和极端气候事件风险变化的一个重要问题。将利用统计方法从气候模式输出得出与极端气候风险相关的年代际气候变率模式，并将通过计算信噪比、复合分析和回归分析以及其他统计方法评估波动的潜在可预测性。该项目的更广泛影响在于它对IPCC第五次评估报告的支持，该报告旨在向全球决策者提供有关气候变化及其后果的信息。年代际气候变率影响着全世界的人们，因此更好地了解年代际变率将具有巨大的社会效益。

This is one of 16 Rapid Response (RAPID) projects funded as the result of a Dear Colleague Letter (NSF 11-006) encouraging diagnostic analyses of climate model simulations prepared for the Intergovernmental Panel on Climate Change Fifth Assessment Report (IPCC AR5). Research conducted in these projects is expected to lead to more detailed model intercomparisons, better understanding of robust model behaviors, and better understanding and quantification of uncertainty in future climate simulations.Research conducted in this project examines decade-to-decade natural variability in the ensemble of simulations of 20th century climate prepared for the AR5. Key questions addressed are 1) What portion of the observed global warming can be explained by natural decadal variability? In particular, to what extent was the mid-20th century warming anthropogenically induced or the result of natural variability? 2) How are decadal oscillations interlinked and how do they modulate extreme climate events such as heat waves and drought, floods and tropical cyclones? 3) How well do the models simulate the decadal variability of late 19th-20th century? One reason these questions are important is that the 20th century record of global-mean temperature contains prominent decadal fluctuations, and the extent to which these occurred as the result of natural variability rather than anthropogenic activity (changes in aerosol forcing, for instance) is not known. Natural decadal fluctuations will continue to be superimposed on anthropogenic warming, and the extent to which these fluctuations are predictable is an important question for understanding and predicting both changes in mean climate and changes in the risk of extreme climate events. Decadal climate variability patterns will be derived from climate model output and related to extreme climate risk using statistical methods, and the potential predictability of the fluctuations will be assessed through calculation of signal-to-noise ratios, composite and regression analyses, and other statistical methods.The broader impact of the project lies in its support of the IPCC AR5, which is intended to provide information on climate change and its consequences to decision makers worldwide. Decadal climate variability affects people all over the world, and a better understanding of decadal variability would thus be of great societal benefit.