On the persistence of shocks to global CO₂ emissions: a historical data perspective (0 to 2014)

Anthropogenic emissions of carbon dioxide (CO₂) are the most important greenhouse gas. However, until now, no research has investigated the persistence of global CO₂ emissions over a very long period of time. This work aims to fill this gap by examining the persistence of shocks to global CO₂ emissions with a dataset of more than 2000 years. To this end, the study applies a battery of unit root tests by considering sharp and smooth structural shifts as well as the frequency domain properties of the series. Lee-Strazicich method results reveal that sharp break dates relate to the influenza pandemic of 1557 and the invention of the steam engine in 1712, and these historical events led to changes in the trend function of CO₂ emissions. The findings of the Fourier Lagrange Multiplier and Fourier wavelet unit root tests illustrate that global CO₂ emissions contain a unit root and do not exhibit mean-reverting behavior, thus external shocks have permanent effects on CO₂ emissions. The results suggest that a reduction in global CO₂ emissions is possible if effective environmental and energy policies established in international meetings such as Rio Conference, Kyoto Protocol Paris Agreement, and the United Nations Sustainable Development Summit are properly implemented.