Arctic Amplification of Anthropogenic Forcing: A Vector Autoregressive Analysis

Abstract

On September 15th 2020, Arctic sea ice extent (SIE) ranked second-to-lowest in history and keeps trending downward. The understanding of how feedback loops amplify the effects of external CO2 forcing is still limited. We propose the VARCTIC, which is a Vector Autoregression (VAR) designed to capture and extrapolate Arctic feedback loops. VARs are dynamic simultaneous systems of equations, routinely estimated to predict and understand the interactions of multiple macroeconomic time series. The VARCTIC is a parsimonious compromise between full-blown climate models and purely statistical approaches that usually offer little explanation of the underlying mechanism. Our completely unconditional forecast has SIE hitting 0 in September by the 2060’s. Impulse response functions reveal that anthropogenic CO2 emission shocks have an unusually durable effect on SIE – a property shared by no other shock. We find Albedo- and Thickness-based feedbacks to be the main amplification channels through which CO2 anomalies impact SIE in the short/medium run. Furthermore, conditional forecast analyses reveal that the future path of SIE crucially depends on the evolution of CO2 emissions, with outcomes ranging from recovering SIE to it reaching 0 in the 2050’s. Finally, Albedo and Thickness feedbacks are shown to play an important role in accelerating the speed at which predicted SIE is heading towards 0.

On Spurious Causality, CO2, and Global Temperature

“…Qualitatively, the impact of annual emissions and cumulative CO 2 -induced forcing shocks on global temperature is vastly similar. In accordance with findings in Goulet Coulombe and Göbel (2021) for the effect of CO 2 on Arctic sea ice extent, the impact of total forcing and CO 2 shocks is highly durable. This time, it is on GMTA rather than sea ice extent.…”

“…This exposition closely follows Goulet Coulombe and Göbel (2021). In time series analysis, the "identification" problem originates from simultaneity in the data.…”

“…Point estimates are nearly identical to that of OLS. For details on such choices in the context of climate data and a more thorough (yet introductory) treatment of IRFs, see Goulet Coulombe and Göbel (2021).…”

“…For a discussion on how to think about "shocks" in a physical system, see Goulet Coulombe and Göbel (2021).…”

[Retracted] Application of Bayesian Vector Autoregressive Model in Regional Economic Forecast

“…Both introduction and removal are based on a given level of significance. On the basis of economic development, maintaining stable and sustained growth in fiscal revenue has always been one of the main goals pursued by the government [4].…”