Arctic climate response to regional aerosol emission changes between 1980 and 2005

Abstract:

Emissions of aerosols and their precursors have due to air quality regulations drastically decreased at northern hemisphere mid-latitudes during the latest decades. At the same time, emissions in the northern hemisphere tropics and subtropics have increased e.g. as a consequence of the strong economic growth in East Asia. Using the fully coupled ocean-atmosphere climate model NorESM, we assess the influence of these regional emission changes on climate with a particular focus on the Arctic. Different mechanisms that couple the localized forcing with the corresponding temperature response are also suggested. The European emission reductions of SO₂ that have taken place since the 1980’s, seem to have had a disproportionally large effect on the Arctic climate compared to the rest of the northern hemisphere. Locally, the Arctic warming due to the decreased SO₂ exceeds 1K. The primary reason for this strong remote temperature response is an increased poleward dry-static heat transport, which is initiated by the enhanced meridional temperature gradient. Emission changes of other aerosol types and over other regions such as North America and Asia appear to have had a much smaller influence on recent Artic climate change. Possible reasons for this differential response will be discussed.