Global evidence of time-frequency dependency of temperature and environmental quality from a wavelet coherence approach

The concern that the global emissions or carbon mitigation plans have not yielded the much desired significant improvement in health, air and environmental quality especially since the Conference of Paris has further created some ambiguities. This has further made environmentalists and policymakers wonder if the December 2015 Paris Climate Agreement is “better than no agreement”. In advancing the studies of global temperature and carbon emission nexus, the current study rather applied the time-frequency dependency of average global mean temperature anomalies and global carbon dioxide (CO2) emissions from fossil fuels for the annual data from 1851 to 2017. The present study uses the wavelet coherence technique and the Toda and Yamamoto causality approach that allows the investigation of both the long- and short-term causal relationship between the global average temperature and global CO2 emissions. The findings of this study indicate that (i) significant vulnerabilities in global average temperature and global CO2 emissions are observed at different time periods and different frequency levels; (ii) global CO2 emissions have a strong power for explaining global average temperature at different time periods; (iii) between 1880 and 1910, global average temperature and global CO2 emissions are positively correlated at medium term; and (iv) the outcome of Toda and Yamamoto causality reveals that global CO2 emissions cause global average temperature and this outcome is in line with the outcome of wavelet coherence approach.