There has been growing interest in the potential of short-lived climate forcer (SLCF) mitigation to reduce near-term global warming. Black carbon (BC), organic carbon (OC), and sulfur dioxide (SO2) are SLCFs which change the Earth's radiative balance directly by affecting radiation, and indirectly by altering cloud properties. We used the ECHAM-HAMMOZ aerosol-climate model to study the radiative forcings due to mitigating the anthropogenic emissions of BC, OC, and SO2 from Chile and Mexico. Limiting our analysis to areas where these emissions had notable effects on both aerosol and clouds, we found that the total radiative forcings of anthropogenic aerosol emissions are different for Chile and Mexico. This was explained by differences in aerosol emissions, orography, and meteorology in these two countries. Especially the radiative forcing for Chilean emissions was influenced by the persistent stratocumulus cloud deck west of Chile. To reduce the uncertainty of our radiative forcing calculations, we nudged the wind and surface pressure toward pre-generated fields. As nudging affects the calculated effective radiative forcing (ERF), we here used the identifier ERFNDG. Our results indicate that the removal of OC and SO2 emissions caused a positive ERFNDG while the removal of BC emissions caused a positive ERFNDG for Chile, but a negative ERFNDG for Mexico. When accounting for co-emission of other aerosol compounds, reducing BC emissions led to positive ERFNDG in both countries. Compared to China, the removal of anthropogenic SO2 emissions in Chile and Mexico caused a much larger global average ERFNDG per emitted unit mass of SO2.

Aerosols and clouds play important roles in the Arctic climate. Conversely, aerosol emissions and cloud formation are affected by changes in the Arctic climate. This paper reviews studies of aerosols and clouds performed during the Arctic Challenge for Sustainability (ArCS) project carried out by the National Institute of Polar Research (NIPR) in Japan and collaborating institutions. The ArCS project included intensive studies of black carbon aerosols (BC). We installed Continuous Soot Monitoring System (COSMOS) instruments to measure atmospheric BC at four locations in the Arctic, establishing the Arctic BC COSMOS Measurement Network (ABCMnet). We also measured BC concentrations in snowpack in extensive areas of the Arctic and showed that previous studies have greatly overestimated BC in snowpack. We developed and improved new aerosol models that achieved better agreements with measurements of BC in the Arctic atmosphere, snowpack, and falling snow. We made new estimates of radiative forcing of BC in the Arctic atmosphere and snow/ice surfaces that lower their albedo. In addition to these researches on BC, we made accurate measurements of ice nucleating particles (INPs) at Ny-?lesund, Svalbard, showing that their concentrations increased in summer as a result of dust particle emissions from glacial outwash sediments. This high ice nucleating ability was likely due to the presence of organic substances mixed with the dust particles. We also made continuous cloud radar measurements and the first continuous in-situ measurements of cloud microphysical properties in the Arctic at Ny-?lesund. Results from these cloud measurements and their relationship with aerosols are described.

A black carbon (BC) emission inventory for Mexico is presented. Estimate was performed by using two approaches, based on fuel consumption and emission factors in a top-down scheme, and the second from PM25 emission data and its correlation with black carbon by source category, assuming that black carbon = elemental carbon. Results show that black carbon emissions are in interval 53-473 Gg using the fuel consumption approach and between 62 and 89 using the sector method. Black carbon key sources come from biomass burning in the rural sector, with 47 percent share to the National total. Mobile sources emissions account to 16% to the total. An opportunity to reduce, in the short-term, carbon dioxide equivalent (CO2-eq) emissions by reducing black carbon emissions would be obtained in reducing emissions mainly from biomass burning in rural housing sector and diesel emissions in the transport sector with important co-benefits in direct radiative forcing, public health and air quality. (C) 2014 Elsevier B.V. All rights reserved.