An Observationally-Based Quantification of Climate Feedbacks

基于观测的气候反馈量化

基本信息

批准号：
NE/E016189/1
负责人：
Piers Forster
金额：
$ 33.15万
依托单位：
University of Leeds
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FE016189%2F1
关键词：
Observationally Based Quantification Climate Feedbacks

项目摘要

The Earth's climate sensitivity / how much it warms as greenhouses gases increase, is arguably the most important 'unknown' in predictions of climate change. Models give a range of approximately 1.5 - 4.5 K for the increase in equilibrium global mean temperature expected when carbon dioxide is doubled. Recently scientists have attempted to use combinations of observations and models to constrain this range / but if anything the range has increased. Uncertainties, mainly in the cloud feedback but also in other feedbacks such as water vapour and ice, account for these large differences between the climate models. These climate feedbacks act to either amplify or reduce the initial effects of the climate change mechanism. Water vapour is the largest positive feedback and acting alone is believed to increase by an amount which roughly doubles the effectiveness of the initial greenhouse gas perturbation. Prime objective: - To evaluate the four main feedback terms in the climate system using observed varaibles. The feedbacks evaluated will be 1) water vapour, 2) clouds (specifically cloud amount, cloud height and cloud optical depth), 3) lapse-rate and 4) surface albedo. A variety of global-scale observations will be combined from many sources and these will be incorporated into offline radiative transfer calculations to gauge the role of these feedbacks in modifying the global energy balance. Uncertainty assessment: - Both the proposed methodology and other more conventional methodologies of calculating climate feedbacks will be assessed in climate model simulations from project partners at the Hadley Centre. These feedback calculations with their model output will be of direct benefit to the Centre who to date have not calculated these feedback terms within their model. These model and data comparisons will be used to: test and assess assumptions used in the proposed methodology, and to quantify realistic uncertainties for each of the feedback terms. - A parallel energy budget calculation by project partners at the NASA Goddard Institute for Space Studies (GISS) will also be used to gauge uncertainty estimates from our analyses. Secondary objectives: - The second aim of the project employs similar methodologies to those of the prime aim to analyse feedbacks on both shorter timescales and on regional scales, and will also analyse feedbacks for different regimes. This work will be used to design diagnostic tests of feedback mechanisms in climate models. Here we will make use of the regime analysis of feedbacks already undertaken by the Hadley Centre. - The third aim of the study is to test the linear model of climate feedbacks: here we will use two different methodologies to evaluate the linear and non linear components of these feeback terms, testing assumptions of non-linearity. Additional output: - We will produce a synthetic dataset of the top-of-atmosphere fluxes, which we will make available to the wider community for their own model evaluation exercises. In summary the project will attempt to quantify some of the largest 'unknowns' in our predictions of global climate change. It will also develop diagnostic tests for feedback analysis in climate models. Overall it will lead to better and more trustworthy climate model predictions, which would not only be of great benefit to the climate modelling community, it would also benefit policy makers who need to rely on the accuracy of such climate model predictions.

地球的气候敏感性 /随着温室气体的增加而变暖的程度，可以说是预测气候变化的最重要的“未知”。对于二氧化碳加倍时，模型的范围约为1.5-4.5 k。最近，科学家试图使用观察值和模型的组合来限制此范围 /，但是如果任何范围有所增加。不确定性，主要是在云反馈中，而且在其他反馈中，例如水蒸气和冰，造成了气候模型之间的这些巨大差异。这些气候反馈作用以扩大或减少气候变化机制的初始影响。水蒸气是最大的积极反馈，据信仅作用会增加一个大约使初始温室气体扰动的有效性翻倍的量。主要目的： - 使用观察到的瓦莱布尔评估气候系统中的四个主要反馈术语。评估的反馈将为1）水蒸气，2）云（特别是云量，云高度和云的光学深度），3）失误率和4）表面反照率。许多来源将合并各种全球规模的观察结果，这些观察结果将纳入离线辐射转移计算中，以衡量这些反馈在修改全球能量平衡中的作用。不确定性评估： - 将在Hadley Center的项目合作伙伴的气候模型模拟中评估拟议的方法和其他更常规的计算气候反馈方法。这些及其模型输出的反馈计算将对迄今为止尚未计算其模型中这些反馈术语的中心有直接的好处。这些模型和数据比较将用于：测试和评估所提出方法中使用的假设，并量化每个反馈术语的现实不确定性。 - NASA戈达德太空研究研究所（GISS）的项目合作伙伴的平行能源预算计算也将用于从我们的分析中评估不确定性估计。次要目标： - 该项目的第二个目标采用与主要目的相似的方法，旨在分析较短的时间尺度和区域尺度上的反馈，并且还将分析不同制度的反馈。这项工作将用于设计气候模型中反馈机制的诊断测试。在这里，我们将利用哈德利中心已经进行的反馈的政权分析。 - 该研究的第三个目的是测试气候反馈的线性模型：在这里，我们将使用两种不同的方法来评估这些费用术语的线性和非线性组件，并测试非线性的假设。附加输出： - 我们将生成大气顶通量的合成数据集，我们将向更广泛的社区提供自己的模型评估练习。总之，该项目将尝试在我们对全球气候变化的预测中量化一些最大的“未知数”。它还将开发用于气候模型中反馈分析的诊断测试。总体而言，它将带来更好，更值得信赖的气候模型预测，这不仅对气候建模社区有很大的好处，而且还将使需要依靠此类气候模型预测准确性的政策制定者受益。