Time-Varying Spillover Effects between Clean and Traditional Energy under Multiple Uncertainty Risk: Evidence from the U.S. Market

The global energy landscape is undergoing an unprecedented transformation with the rapid development of clean energy and the continued significance of traditional energy creating a complex dynamic relationship. This study employs the TVP-QVAR-DY model to systematically examine the dynamic spillover effects between clean and traditional energy markets in the United States, focusing on the impacts of economic policy uncertainty (EPU) and geopolitical risk (GPR). The findings reveal (1) significant time-varying spillover effects between the two markets, with total spillover effects ranging from 30% to 50%, intensifying during extreme events; (2) increases in EPU and GPR exacerbate uncertainty in energy markets, particularly in the traditional energy sector, with spillover effects from crude oil to natural gas reaching 23.60% and vice versa at 24.30%; and (3) in the short term, the clean energy market is influenced by traditional energy, with spillover effects from oil to clean energy at 5.10%, while in the medium to long term it gradually becomes independent and inversely affects the traditional energy market, contributing 2.94% to oil spillovers. The results indicate that as the global energy transition deepens, the clean energy market is shifting from a risk receiver to a risk contributor. Based on these findings, the study proposes policy recommendations including accelerating energy structure transition, managing macroeconomic uncertainty risks, coordinating domestic and international energy markets, and leveraging market mechanisms.