TRANSCLIMA

Project PID2021-123686OB-I00 · University of the Basque Country UPV/EHU

Behaviour is the missing half of climate policy

What 24 experiments and surveys with more than 14,000 participants tell us about carbon pricing, climate communication and the demand side of the energy transition.

TRANSCLIMA · Opportunities in the transition towards a low-carbon economy: stimulating low-carbon consumption through behavioural incentives and nudges · 2022–2026

Download the report (PDF)
A broad flow labelled policy instrument moves left to right; part of it diverts downwards as a behavioural leak and the narrower remainder arrives as abatement delivered.

In numbers

An evidence base built to be checked, not to be taken on trust.

The data behind every figure are deposited in open access in Zenodo and the Open Science Framework, under a CC BY 4.0 licence.

Findings

Ten results that change how policy should be designed.

The mechanism, in one diagram

The project's central result is not that carbon pricing fails. It is that the same increase behaves in two different ways depending on how it is presented, and that the difference runs through a moral route rather than an economic one.

Two routes from the same 15 per cent increase. Unexplained, it lowers purchase intention. Identified as a carbon tax, it raises moral self-concept and purchase intention holds up.
Two routes out of the same price increase. Presented without explanation the price signal works; identified as a carbon tax it is offset by the moral credit the payment confers. The gap between the two is the size of the leak. Diagram drawn for this page from the results of Hartmann, Marcos & Barrutia (2023), Global Environmental Change 78, 102635.

    And, from the project's most recent study

    Extreme protest reduces support for the climate movement whoever it targets — but what the public withdraws is support for the activists' actions, not for the cause. Target choice interacts with the audience's politics: protests against a wind energy company cost most with the audience most disposed to support the transition.

    Change in movement support by protest target: oil company −0.63, bank funding oil exploration −0.59, wind energy company −0.40.
    Extreme protest costs support against every target. Change in movement support relative to moderate protest, in a preregistered 2 × 3 experiment with 1,199 politically balanced US participants. Kazmi, Marcos & Hartmann (2026), Journal of Environmental Psychology 114, 103183. Chart redrawn from the published values.

    Toolbox

    For each instrument: the intended mechanism, the response we observed, and the design fix.

    InstrumentObserved responseDesign implication

    The report sets out thirteen instruments and states, for every row, the design behind it: randomised experiments support causal claims about the manipulated treatment; cross-sectional surveys support associations only.

    Recommendations

    Ten propositions addressed to the people who decide.

    Publications

    The evidence is published, and almost all of it is open access.

      The primary sources are listed here; the report's evidence base lists them all. Across the project the team published thirty-two peer-reviewed articles and nine book chapters. Accepted versions are deposited in ADDI, the UPV/EHU institutional repository.

      Work with us

      The project has ended; the research capability has not.

      If your organisation is designing an instrument, a campaign or a labelling format, we can test it before it is deployed. Tell us what you are working on and we will come back to you.