The role of mineral-dust aerosols in polar temperature amplification

Abstract

Changes in global temperature are generally more marked in high than in low latitudes, an effect referred to as polar amplification. Model simulations of future climate suggest a marked response of high-latitude climate due to elevated greenhouse-gas concentrations and associated albedo feedbacks. However, most climate models struggle to reproduce the amplitude of polar temperature change observed in palaeoclimatic archives and may carry this bias into future predictions. With the example of mineral dust we show that some atmospheric aerosols experience an amplified high-latitude response to global changes as well, a phenomenon generally not captured by the models. Using a synthesis of observational and model data we reconstruct atmospheric dust concentrations for Holocene and Last Glacial Maximum (LGM) conditions. Radiative forcing calculations based on our new dust concentration reconstructions suggest that the impact of aerosols in polar areas is underestimated in model simulations for dustier-than-modern conditions. In the future, some simulations predict an increase in aridity in dust source areas. Other aerosols such as black carbon and sulphates are likely to increase as well. We therefore suggest that the inclusion of the amplified high-latitude response of aerosols in atmospheric models would improve the assessment of LGM and future polar amplification. © 2013 Macmillan Publishers Limited. All rights reserved.