Climate Policy Polarization

Last registered on January 22, 2026
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Pre-Trial

Trial Information

General Information

Title
Climate Policy Polarization
RCT ID
AEARCTR-0017443
Initial registration date
December 11, 2025

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
January 22, 2026, 5:47 AM EST

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Locations

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Primary Investigator

Name
Eva Hümmecke
Affiliation
RWI – Leibniz Institute for Economic Research
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Other Primary Investigator(s)

PI Name
Mark A. Andor
PI Affiliation
RWI – Leibniz Institute for Economic Research
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PI Name
Christoph Feldhaus
PI Affiliation
Ruhr University Bochum
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PI Name
Andreas Löschel
PI Affiliation
Ruhr University Bochum
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PI Name
Leon Landes
PI Affiliation
Ruhr University Bochum
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Additional Trial Information

Status
In development
Start date
2025-12-12
End date
2030-12-31
Keywords
Behavior, Environment & Energy, Governance
Additional Keywords
Climate Policy, Polarization, Social Divide, Beliefs
JEL code(s)
D72, D91, Q58
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
Public debate on climate policy has grown increasingly heated, accompanied by rising polarization within the population. This study examines the extent to which disagreements over federal climate policies generate affective polarization. We run an experiment with 9,000 participants in Germany, Spain, and the United States. We compare polarization arising from opposing views on the ambition of the current federal climate policy and from differing preferences for specific policy instruments. During the experiment we elicit policy preferences, measure pro climate behavior, and capture beliefs about the motivations and behaviors of others. Finally, we measure affective polarization through two incentivized dictator games with other participants who share or oppose the policy view, respectively. Additionally, we exogenously vary information about others pro-climate behavior to investigate the causal impact of these beliefs on polarization.
External Link(s)

Registration Citation

Citation
Andor, Mark A. et al. 2026. "Climate Policy Polarization." AEA RCT Registry. January 22. https://doi.org/10.1257/rct.17443-1.0
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Experimental Details

Interventions

Intervention(s)
Intervention Start Date
2025-12-12
Intervention End Date
2026-01-15

Primary Outcomes

Primary Outcomes (end points)
Reasons driving policy preference across several motives,

Climate donation behavior and beliefs about climate donation behavior (in-group and out-group)

Polarization measured as the difference between the amount a participant allocates to an in-group member and the amount allocated to an out-group member in the dictator game
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The core of our experiment involves measuring beliefs and affective polarization by first distinguishing participants based on their views about the ambition of current climate policy and then exposing those favoring greater ambition to climate policies within specific policy contexts. Across these contexts, we compare polarization rooted in disagreement over the overall extent of climate policy with polarization stemming from differing preferences for specific policy instruments.

A randomized information shock about others’ donation behavior then provides exogenous variation to identify how revised beliefs about pro-climate actions by in-group and out-group members causally shape climate-related polarization.
Experimental Design Details
Not available
Randomization Method
Randomization by the survey institute commissioned to conduct the survey
Randomization Unit
Individuals
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
9,000 respondents (3,000 per country: US, Spain and Germany)
Sample size: planned number of observations
9,000 respondents (3,000 per country: US, Spain and Germany)
Sample size (or number of clusters) by treatment arms
K1: Participants who believe that the federal government’s climate policy goes (somewhat) too far
K2: Participants who believe that the federal government’s climate policy does not go (quite) far enough

Participants in K2 are further split into three subgroups:

K2_G1: Control group (no assessment of preferences for specific climate policy)
(1/3 of participants in K2)

K2_G2: Assessment of policy preferences within the heating sector
(1/3 of participants in K2)

K2_G3: Assessment of policy preferences within the mobility sector
(1/3 of participants in K2)

Information provision belief shock:
Within each of the four groups (K1, K2_G1, K2_G2, K2_G3), participants are randomly split evenly into one control condition and three treatment conditions

Control group sizes belief shock:
- K1 control group: 1/4 of participants in K1
- K2 control groups: 1/4 of each K2 subgroup, i.e.
1/12 of all participants from K2 per control group creating three separate K2 control groups (one for G1, G2, and G3 respectively)

Treatment group sizes belief shock:
- K1 treatment groups: 3/4 of participants in K1 creating three treatment groups for K1
- K2 treatment groups: 3/4 of each K2 subgroup, i.e.
1/12 of all participants from K2 per treatment group, creating three treatment groups within each subgroup (K2_G1, K2_G2, and K2_G3) and therefore nine separate K2 treatment groups
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
German Association for Experimental Economic Research e.V.
IRB Approval Date
2025-11-24
IRB Approval Number
d6kaHzDq
Analysis Plan

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