The Expectations Channel of Climate Change (ECCC)

气候变化对经济的影响是高度不确定的。它的全部范围可能要经过几十年（如果不是几百年的话）才能显现出来。相反，对气候变化的期望已经抓住了人们的头脑，近年来越来越多。这就产生了一个新的现象：对气候变化的预期影响着今天的经济决策，从而比实际的气候变化对经济的影响要强烈得多--当然也更早。在这个项目中，我们试图通过追求两个目标，在各个层面上研究这一现象，简称“气候变化预期”。其中一个目标是进行一项代表德国人口的在线调查，以衡量气候变化的预期。调查将分为四波半小组（为期一年）。它使我们能够衡量气候变化的预期及其决定因素，无论是在横截面和随着时间的推移。我们还将进行信息处理，以产生气候变化预期的外生变化。我们利用这种变化来衡量随着时间的推移，气候变化预期对（报告的）消费和储蓄决策的因果影响。第二个目标是研究气候变化预期对商业周期的影响。我们在一个定量的商业周期模型中这样做。作为一个独特的特征，这个模型允许通过“诊断性预期”偏离理性预期。通过这种方式，我们可以研究预期的变化是如何发生的，这些变化不是植根于基本面，而是由于“不断变化的叙述”。例如，与气候变化相关的大型自然灾害的概率可能会发生变化，而客观概率不会发生任何变化。通过这种方式，我们的项目不仅推进了我们对气候变化（预期）如何影响经济以及我们生活方式的理解，而且还为最近旨在捕捉经济学中预期形成过程的性质和影响的努力提供了信息。

The economic impact of climate change is highly uncertain. Its full extent is likely to become apparent only over the course of several decades (if not centuries). Expectations about climate change, instead, are already capturing peoples’ mind and increasingly so in recent years. This gives rise to a new phenomenon: expectations about climate change influence economic decisions today and thus impact the economy much more strongly – and certainly earlier – than actual climate change. In the project we seek to study this phenomenon, “climate-change expectations” for short, at various levels by pursuing two objectives. One objective is to run an online survey representative of the German population to measure climate-change expectations. The survey will come in a semi-panel of four waves (over the course of one year). It permits us to measure climate-change expectations and their determinants, both in the cross-section and over time. We will also perform information treatments in order to generate exogenous variation in climate-change expectations. We exploit this variation to measure the causal effect of climate-change expectations on (reported) consumption and saving decisions over time. The second objective is to study the effect of climate-change expectations on the business cycle. We do so within a quantitative business-cycle model. As a distinct feature, this model allows for a departure from rational expectations via “diagnostic expectations”. In this way, we can study how shifts in expectations that are not rooted in fundamentals but due to “changing narratives” play out. For instance, the probability assigned to large, climate-change related natural disasters may shift without any change in the objective probability. In this way, our project advances not only our understanding of how (expectations of) climate change impact the economy and thus our way of life, but also informs recent efforts aimed at capturing the nature and implications of the expectation formation process in economics.