Research

An important driver of climate change inaction is the belief that individuals cannot have any tangible impact on climate change through their own actions. Currently available statistics are not suited to systematically assess or challenge this belief. In this paper, I derive the marginal impact of emission reductions – the effect of reducing emissions by 1 tonne of CO₂ (tCO₂) – on physical climate change outcomes, document important misperceptions, and show how they affect behavior. Using climate models, I find that the impact of reducing emissions by 1 tCO₂ is 4.000 liters less glacier ice melting, 6 additional hours of aggregate life expectancy, and 5 m² less vegetation undergoing ecosystem change. Subjects underestimate these figures by orders of magnitude. Moreover, their mental model is inconsistent with climate models. First, they assume that the marginal impact increases when others reduce their emissions (strategic complementarity). Second, they think emission reductions are a threshold public goods game. Providing subjects with the climate scientific findings causally increases perceived self-efficacy, intentions to reduce emissions, and real donations to offset emissions. The findings are consistent with a model of threshold thinking, which predicts positive overall emission reductions of information provision in equilibrium.

We lay out a simple framework for optimal green retailing. We use it to evaluate a heavily publicized campaign in which a large German grocer added uninternalized environmental externality costs, which we estimated using “true cost accounting”, to a selection of products and donated the proceeds to environmental conservation. The implied demand elasticity with respect to the campaign price increase was half of the elasticity with respect to standard short-term promotional price decreases, suggesting that demand may have shifted out significantly due to warm glow from the donations. We find that the campaign increased overall welfare. Surveys show that the campaign did not substantially affect beliefs about externality magnitudes, but consumers expressed concerns about greenwashing and viewed true cost pricing more skeptically after the campaign. Using a structural model and home scanner data, we evaluate alternatives such as a cross-subsidy from high- to low-externality foods and the first-best system of externality taxes.

Optimal climate change mitigation requires easily understandable estimates of the benefits of marginal emission reductions. Currently, such estimates are not readily available. Here we propose a general framework for estimating the impact of marginal emission reductions from climate model projections. The marginal impact is the change in a climate change outcome due to reducing emissions by 1 tCO₂ today, holding others’ actions constant. We estimate the marginal impact for 19 climate change outcomes: livestock production, Arctic sea ice, biome shift, coral reefs, crop failure, crop production, droughts, fish mass, glacier ice, heat mortality, heatwaves, livestock welfare, ocean heat, permafrost thaw, radiative forcing, river floods, snow cover, ocean expansion, and wildfires. We provide the estimates as a function of the outcome time horizon. Moreover, we analyze the variance in the estimates stemming from six sources of uncertainty included in the analysis: climate models, impact models, functional form of the emulator, statistical parameters, temperature response to emissions, and future overall emissions.

The consumption of meat and other animal products have large externalities on health care spending, climate change and animal welfare. Reducing their consumption is therefore often seen as key in addressing these problems. Yet, there is little causal evidence for many determinants of meat consumption. We leverage a unique dataset of over 200 million home deliveries from restaurants and supermarkets in over 30 countries to study the role of movies, news and the availability of plant-based meat alternatives in reducing meat consumption. We exploit the high time frequency of the data together with the timing of movie releases, news coverage and introduction of new items at nearby food providers for causal identification.

Many consumers engage in ethical consumption, altering their consumption choices so as to mitigate their personal contributions to negative externalities such as climate change, animal welfare, or pollution. But do individual consumption choice have any impact on overall externalities in a competitive market? In this paper, we estimate the effect of consumption changes on externalities in general equilibrium for the U.S. meat market. We derive sufficient statistics based on the demand and supply cross-price elasticities of all goods with externalities. We estimate the elasticities using home scanner data and farmer surveys, respectively, and derive the effect of ethical meat consumption on animal welfare. We further show that the effect on other externalities can be estimated using bounding assumptions on substitution patterns. Using such assumptions, we also estimate the effect of ethical meat consumption on overall greenhouse gas emissions.

A key issue in science is assessing robustness to data analysis choices, while avoiding selective reporting and providing valid inference. Specification Curve Analysis is a tool intended to prevent selective reporting. Alas, when used for inference it can create severe biases and false positives, due to wrongly adjusting for covariates, and mask important treatment effect heterogeneity. As our motivating application, it led an influential study to conclude there is no relevant association between technology use and teenager mental well-being. We discuss these issues and propose a strategy for valid inference. Bayesian Specification Curve Analysis (BSCA) uses Bayesian Model Averaging to incorporate covariates and heterogeneous effects across treatments, outcomes and sub-populations. BSCA gives significantly different insights into teenager well-being. It provides strong evidence that technology has relevant associations with teenager well-being: (1) well-being is negatively associated with electronic device usage, (2) social media use is negatively associated with self-assessed well-being but positively associated with parent-assessed well-being, and (3) has a stronger negative association with self-assessed well-being for girls compared to boys.

HM Treasury’s estimation of the economic consequences of Brexit – using standard macroeconomic models – during the EU referendum campaign represents a remarkable intervention in a highly politicized public debate. It raises a series of questions about the use of economic expertise. Through a detailed theoretical and empirical critique of the Treasury’s methodology – and a reassessment of the likely effects of Brexit in light of this – we cast doubt on the utility of their approach, highlighting methodological issues, unrealistic assumptions, and misrepresentations of established facts. In the process we seek to identify some of the wider implications for the use and potential abuse of economic expertise in highly charged political contexts, such as the EU referendum debate.

A basic but as yet unachieved goal for UN missions is to know the exact locations of their peacekeepers at any given time. Such tracking would help field missions plan operations, avoid and respond to ambushes, kidnappings and friendly fire incidents, rapidly send reinforcements and retrieve wounded peacekeepers, ultimately saving lives. Improved effectiveness could be obtained from ‘precision peacekeeping’, where soldiers, police and civilians are deployed to precise locations and events, while operational leaders follow their movements. Fortunately, tracking technology has improved considerably so that commercial solutions for real-time tracking of personnel and vehicles are now available at lower cost and increased accuracy and sophistication, while being more user-friendly. The advances in phone and vehicle tracking systems are reviewed here to identify the benefits, drawbacks and challenges, especially any political ones, for the United Nations. The world organization can benefit from modern blue mission tracking, without having to develop costly, customized solutions. Such initiatives have few technological or financial hurdles but the politics and institutionalization of continuous positional surveillance needs policy modernization, guided by a nuanced understanding of technological empowerment.