The Marginal Impact of Emission Reductions: Behavior

Last registered on March 05, 2026
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Pre-Trial

Trial Information

General Information

Title
The Marginal Impact of Emission Reductions: Behavior
RCT ID
AEARCTR-0017847
Initial registration date
February 26, 2026

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
March 05, 2026, 6:16 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
Christoph Semken
Affiliation
University of Toronto
Contact Primary Investigator

Other Primary Investigator(s)

Additional Trial Information

Status
In development
Start date
2026-02-28
End date
2026-03-28
Keywords
Behavior, Environment & Energy
Additional Keywords
climate change, beliefs, mental models, information provision, climate policy
JEL code(s)
Q54, Q51, D83, C91, Q58
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
An important driver of climate change inaction is the belief that individuals cannot have any tangible impact on climate change through their own actions. In this experiment, I provide treated participants with estimates of the marginal impact of emission reductions derived from climate models. I measure the impact of the information on donations to reduce emissions.
External Link(s)

Registration Citation

Citation
Semken, Christoph. 2026. "The Marginal Impact of Emission Reductions: Behavior." AEA RCT Registry. March 05. https://doi.org/10.1257/rct.17847-1.0
Sponsors & Partners

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Experimental Details

Interventions

Intervention(s)
Participants are randomly divided into a treatment and a control group.

- Treatment: Participants see information pages summarizing the climate-scientific results (marginal impact point estimates, continuity, and strategic substitutability), plus a video summary.
- Control: Participants do not receive the information pages described above.
Intervention Start Date
2026-02-28
Intervention End Date
2026-03-28

Primary Outcomes

Primary Outcomes (end points)
Amount donated in the donation task (GBP, z-scored)
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
Summary: Individually randomized, two-arm experiment (treatment vs control). After explainers, treated participants receive information pages and a video summary. Participants then complete a donation task where they choose how much to donate (GBP) to atmosfair.

Context before randomization: Participants in both treatment groups see a definition and explanation of global warming. They also see the statement that 1 tCO2 is created by driving about 4,000 miles with an average diesel car.

Engagement/obfuscation: On each explainer and information page, participants rate how surprising they find the information (4-item Likert scale).

Donation task: Participants can receive up to £200 and choose how much to donate to reduce global CO2 emissions via atmosfair (carbon offsets). Donation choice uses a slider from £0 to £200. An alternative slider allows choosing the amount of emission reductions (sliders synchronized). It costs about £20 to reduce emissions by 1 tCO2 in this way. Two respondents are randomly selected. If selected, their decision is implemented and the amount they keep is added to their bonus.

For details, including the full survey, see the pre-analysis plan.
Experimental Design Details
Not available
Randomization Method
Computer random number generator
Randomization Unit
Individual participant
Was the treatment clustered?
No

Experiment Characteristics

Sample size: planned number of clusters
600 participants
Sample size: planned number of observations
600 participants
Sample size (or number of clusters) by treatment arms
300 participants each
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Monte Carlo power analysis using pilot data: Pilot treatment effect = 0.23 standard deviations (donation outcome, z-scored). With 600 participants, 1,000 simulations predict 91.0% power to detect this treatment effect at the 5% significance level.
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
University of Toronto Social Sciences, Humanities and Education Research Ethics Board
IRB Approval Date
2025-11-18
IRB Approval Number
49676
Analysis Plan

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