Soot climate forcing via snow and ice albedos

Abstract

Plausible estimates for the effect of soot on snow and ice albedos (1.5% in the Arctic and 3% in Northern Hemisphere land areas) yield a climate forcing of ؉0.3 W͞m 2 in the Northern Hemisphere. The ''efficacy'' of this forcing is Ϸ2, i.e., for a given forcing it is twice as effective as CO 2 in altering global surface air temperature. This indirect soot forcing may have contributed to global warming of the past century, including the trend toward early springs in the Northern Hemisphere, thinning Arctic sea ice, and melting land ice and permafrost. If, as we suggest, melting ice and sea level rise define the level of dangerous anthropogenic interference with the climate system, then reducing soot emissions, thus restoring snow albedos to pristine high values, would have the double benefit of reducing global warming and raising the global temperature level at which dangerous anthropogenic interference occurs. However, soot contributions to climate change do not alter the conclusion that anthropogenic greenhouse gases have been the main cause of recent global warming and will be the predominant climate forcing in the future. (2) suggests that the fossil fuel BC forcing is larger, Ϸ0.5 W͞m 2 . J.H. and colleagues (3-5) have argued that the total anthropogenic BC forcing, including BC from fossil fuels, biofuels, and outdoor biomass burning, and also including the indirect effects of BC on snow͞ice albedo, is still larger, 0.8 Ϯ 0.4 W͞m 2 . Here we estimate the magnitude of one component of the BC climate forcing: its effect on snow͞ice albedo.Several factors complicate evaluation of the BC snow͞albedo climate forcing and dictate the approach we use to estimate the forcing.

Sensitivity of Greenland Ice Sheet surface mass balance to surface albedo parameterization: a study with a regional climate model

“…In contrast, black carbon concentrations of 0.05 ppmv have been measured at Summit, Greenland (Flanner et al, 2007), and probably even higher concentrations are present in the lower regions. This will have a significant impact on snow albedo (Hansen and Nazarenko, 2004;Flanner et al, 2007). The effect of black carbon on broadband snow albedo in RACMO2 follows Eq.…”

Arctic warming, moisture increase and circulation changes observed in the Ny-Ålesund homogenized radiosonde record

“…The interplay of the retreating sea ice cover and the atmosphere includes radiation-based concepts as the snow/icealbedo feedback, with less high reflective sea ice (or snow cover) exposing more open water (or dark underlying) surface to absorb solar radiation and further trigger the warming and melting. Further reduction in Arctic albedo is related to soot on snow and on sea ice linked to fossil burning (Hansen and Nazarenko 2004;Marks and King 2013) and heat-absorbing black carbon aerosols in the atmosphere (Shindell and Faluvegi 2009). More importantly, the changes in sea ice extent affect the vertical heat fluxes between the Arctic Ocean and the overlying atmosphere (Serreze et al 2009;Screen and Simmonds 2010).…”

A long-term Global LAnd Surface Satellite (GLASS) data-set for environmental studies

“…The recession of snow cover associated with warm periods in the Earth's history has led to greater absorption of solar energy (and hence amplified warming). Aerosols such as dust and soot may also greatly contaminate snow and reduce its albedo (Hansen and Nazarenko 2004;Xu et al 2009). …”