Volatility spillover between carbon market and related markets in time-frequency domain based on BEKK-GARCH and complex network analysis

With rising public attention to climate issues and sustainable development, the connection between carbon market and its related markets has become closer. Based on BEKK-GARCH method and complex network theory, this study tries to explore the volatility spillover effects and network topology among China's carbon market, non-renewable energy market, renewable energy market, high-tech market and climate policy uncertainty index in time-frequency domain. It is found that, firstly, there are significant asymmetric volatility spillover effects among the markets. Secondly, the spillover effects between markets are time-varying, especially during crisis periods in which they are significantly higher than that during the stable period. Thirdly, with time increasing, the closer the connection between markets. In the long run, the closeness of the connection is directly proportional to the spillover effect. Finally, climate policy uncertainty is the main risk source. For full sample, from perspective of frequency domain, non-renewable energy and carbon markets are the main risk recipients. Based on the findings, it should step up efforts on market monitoring and intervention during crisis periods, strengthen cross-market risk management, pay attention to climate uncertainty and time-frequency varying characteristics of volatility spillovers, so as to provide useful information for policy makers and investors.