Seminar

Abstract

Several modeling studies in the past decade have attributed a significant fraction of northern hemisphere and Arctic warming to the darkening of surface snow and sea ice by black carbon. Because of snow and ice's very high albedo and because of the albedo feedback that results with snow and ice melt, darkening of snow and sea ice is very effective at producing climate warming. The results of these model studies have generated considerable interest in the policy community. However, accurate knowledge of the sources and magnitude of snow BC forcing for decision-making and work is still needed to test and constrain the model results. Until recently very few measurements of snow and sea ice BC were available to test the model studies. In this talk I will present the results of a recent survey of Arctic snow and sea ice BC concentrations and sources, and I will discuss the advantages and disadvantages of different methods for measuring snow BC concentrations. Constraining snow BC concentrations is only one factor that determines climate warming by BC in the cryosphere, so in addition I will discuss other sources of uncertainty in the modeled radiative forcing and climate response which need to be examined.