Cepni, OguzhanGil-Alana, Luis A.Gupta, RanganPolat, Onur2025-07-032025-07-032025-06Cepni, O., Gil-Alana, L.A., Gupta, R. et al. 2025, 'Time-variation in the persistence of carbon price uncertainty : the role of carbon policy uncertainty', Quarterly Review of Economics and Finance, vol. 102, art. 102004, pp. 1-8, doi : 10.1016/j.qref.2025.102004.1062-9769 (print)1878-4259 (online)10.1016/j.qref.2025.102004http://hdl.handle.net/2263/103133We estimate models of fractional integration to determine the degree of persistence for two recently developed metrics of carbon price uncertainty: the Carbon VIX and Carbon Implied Volatility (CIV) covering the period of the 1st week of September 2013 to the 4th week of December 2022. First, we find the two metrics to be highly persistent but depicting mean-reversion with long-memory. Second, time-varying (recursive) estimation revealed that the underlying persistence is on a downward trend. Third, we show that the recent reduction in persistence of carbon price uncertainties is a result of declining carbon policy uncertainty — a metric we develop using aggregate information on squared surprises of carbon futures price of various maturities. Given that carbon price uncertainty has been shown to negatively affect decarbonization investments, our findings have important implicati HIGHLIGHTS • Persistence of the Carbon VIX and Carbon Implied Volatility (CIV) estimated. • Long-memory models used for weekly data over 2013–2022. • The two metrics are highly persistent but depict mean-reversion. • Time-varying persistence is on a downward trend. • The reduction in persistence is a result of declining carbon policy uncertainty.en© 2025 The Author(s). Published by Elsevier Inc. on behalf of Board of Trustees of the University of Illinois. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Carbon implied volatility (CIV)European Union Emissions Trading System (EU-ETS)Carbon price uncertaintyFractional integrationPersistenceRegulatory eventsCarbon policy uncertaintyCarbon VIXArticle