Why don't Black Carbon and climate models get along?

Modelling the impacts of Black Carbon (BC) is in abundance in academic geography. However, only recently has Black Carbon begun to be incorporated into studies modelling climate change (ie. ice sea ice retreat) within the Arctic. Either models have advanced (and details such as BC can be accounted for) or black carbon has just been established as contributor to climate change in the Arctic, I do not know. This post sums up my series on black carbon as a form of long range pollution and aims to discuss the presence of black carbon in modelling studies by comparing two studies.

Published in 1995, Cattle and Crossley, discuss the basic predictions of climate change in the Arctic region. The model adopted is that used by the Hadley centre for climate prediction and research at the meteorological office, to model the impacts of future climate change resulting from increased concentrations of greenhouse gases. It is important to remember climate change did not become a global phenomenon till the late 20^th so this knowledge was quite new at this time. The results suggested a temperature change by approximately 2 degree centigrade by 2030 (this is based on Greenland predictions but generally results varied very little), thus causing a thinning of ice and a maximum ice thicknesses of 3m in March and 2m in September (within the central Arctic).

This seems to be a very large underestimate of what has occurred over the past 10 or so years. Currently, 4 years before the predicted temperature rise, parts of the Arctic are witnessing temperature rises of 2-3 degrees PER DECADE! So by 2030 this temperature change will be well above what the model simulations in Castle and Crossley's study. This gap between predicted and observed results could have resulted from a lack of consideration of the albedo feedback systems created by black carbon. Having said this it is unlikely black carbon could be able to single handedly cause an accelerated rate of sea ice retreat. Graversen et al (2008) suggest black carbon and the resulting change to albedo could contribute to the warming when associated with warming of the middle troposphere (as a result of an advection of energy bringing warmer air into the Arctic region).

Map showing sea ice retreat.

In order to accurately predict abrupt sea ice retreat, anthropogenic forcing, such as the influence of particulates, must be incorporated within Arctic Models. Holland et al (2006) incorporate changes to albedo (as a result of anthropogenic particulates) as a forcing of sea ice reduction. The study concludes major summer ice reduction could be expected as early as 2015. A focus is placed on the influence of surface albedo feedbacks accelerating retreat. So we are currently in 2015 and have experienced the predicted sea ice retreat. The map (Right) shows the sea ice retreat between the extents in December 2015. The magenta line represents the median ice edge for 1980-2010 and just illustrates the overall sea ice loss occurring within the past 5 years.

To sum up, in order to create accurate simulations, models must include anthropogenic forcing from pollutants such as black carbon, to realistically represent albedo feedback systems. The extent of the influence of black carbon on warming is questionable and some studies such the UNEP/WMO Assessment, conducted by the World Bank, does not consider the forcing properties of the particulates. The influence of sources of black carbon in this study is deemed so insignificant (in comparison to other forcing factors), so it is not included. Furthermore the level of uncertainty associated with the calculation of the forcing effect of black carbon is so high it contradicts it inclusion in some cases. However, the literature still generally suggests to achieve realistic results black carbon should be included in Arctic models.