Abstract
The mechanisms behind Arctic warming and associated climate changes are difficult to discern. Also, the complex local processes and feedbacks like aerosol-cloud-climate interactions are yet to be quantified. Here, using the Community Earth System Model (CAM5) experiments, with emission enhancement of anthropogenic sulfate 1) five-fold globally, 2) ten-times over Asia, and 3) ten-times over Europe we show that regional emissions of sulfate aerosols alter seasonal warming over the Arctic, i.e., colder summer and warmer winter. European emissions play a dominant role in cooling during the summer season (0.7 K), while Asian emissions dominate the warming during the winter season (maximum ∼0.6 K) in the Arctic surface. The cooling/warming is associated with a negative/positive cloud radiative forcing. During the summer season increase in low–mid level clouds, induced by sulfate emissions, favours the solar dimming effect that reduces the downwelling radiation to the surface and thus leads to surface cooling. Warmer winters are associated with enhanced high-level clouds that induce a positive radiative forcing at the top of the atmosphere. This study points to the importance of international strategies being implemented to control sulfate emissions to combat air pollution. Such strategies will also affect the Arctic cooling/warming associated with a cloud radiative forcing caused by sulfate emission change.
Highlights
The Arctic is warming, which is of great concern because of the twofold rise in surface temperature compared to the rest of the world (Cohen et al, 2014; Stjern et al, 2019)
We found different Arctic temperature changes for summer (colder summers) and winter (warmer winters)
Our analysis shows that sulfate emission enhancements, both regionally and globally, produce a clear seasonal shift in the temperature from colder summer to warmer winter
Summary
The Arctic is warming, which is of great concern because of the twofold rise in surface temperature compared to the rest of the world (Cohen et al, 2014; Stjern et al, 2019). This enhanced Arctic warming is known as Arctic amplification. The recent increase in anthropogenic activities in the Arctic and its vicinity is one of the factors that amplify climate change in addition to remote influences (Acosta Navarro et al, 2016).
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