Disentangling Regional Climate Change: Assessing the contribution of global– and regional–scale anthropogenic drivers to observed regional warming

While the influence of well-mixed greenhouse gas emissions on global warming is well-documented and robustly attributed through multiple lines of evidence, regional attribution remains more challenging and dependent on the performance and resolution of climate models. This study proposed an observational-based statistical analysis utilizing the real-time Global Warming Index (GWI) to investigates the extent to which observed regional temperature trends are attributable to global-scale anthropogenic factors, mainly the direct effects of CO₂, aiming to differentiate the portion of the change attributable to regional-scale drivers (such as regional industrial aerosols, black carbon aerosols, and land-use/land-cover change, etc).

To quantify the contribution of global– and regional–scale climate drivers to observed temperature change, I performed regression analyses using the HadCRUT4 temperature data and the Global Warming Index (GWI). The GWI, calculated through a least squares method, correlates observed global average temperatures with expected responses to global radiative forcing series. 

Results indicate that in certain regions — specifically West Asia, East N. America, West Africa, and the Amazon basin — 62±7%, 61±13%, 58±7%, and 61±10% of the warming observed over 1991-2020 can be attributed to global anthropogenic warming, primarily the direct effects of CO₂. The remaining portion, which represents 22±8%, 21±16%, 27±9%, 23±14% of the observed warming, is attributable to regional climate drivers. The Mediterranean showcases high sensitivity, with regional drivers contributing 31±13% of the observed 1.2°C warming, amplifying the warming attributed to global anthropogenic drivers. The Arctic Ocean along with the Russian-Arctic region exhibits a substantial contribution from regional drivers and local feedback mechanisms to the observed warming amplification, quantified at 43±15% of the 3°C warming over 1991-2020. Regional cooling drivers, however, are significant in East Asia and the Tibetan Plateau, with the latter experiencing a cooling contribution of -42±17% (with a ±95% uncertainty due to internal variability derived from control simulations).

The novel approach presented in this study helps in understanding how different scales of climate change drivers contribute to local temperature change. This understanding can foster more effective, localized mitigation strategies that complement global efforts to address climate change.