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The geopolitics of black carbon
There are concerns that focus on black carbon can change the geo politics of climate mitigation responsibility. Developing countries still trapped in poorer technologies that burn fuels inefficiently may be blamed for climate impacts and pushed for tougher climate action. There are apprehensions that the new science can be misused. The developed nations that are the biggest emitters of CO2 and under the common but differentiated principle have the larger responsibility for early action to allow developing countries to improve energy access and grow, may delay action on CO2 mitigation. The UNEP Integrated Assessment Report of 2012 shows that Northeast Asia, Southeast Asia and the Pacific account for the largest share of global black carbon emissions. China accounts for 60-80 percent of the emissions in the region. North America and Europe account for second largest share.
The hint of this politics was evident way back in 2002 when a storm was set off by the United Nations Environment Programme (UNEP) report on the "Asian brown cloud" that highlighted the influence of particulate pollution over South Asia on the global and regional weather systems. It pointed out that pollutants and particles from biomass burning and industrial emissions had formed a three-kilometre-thick brownish layer over many regions in Asia. It made a direct link between this pollution build-up and disruption in rainfall and wind patterns. A 10 per cent reduction in solar energy reaching the region's oceans was causing a corresponding decrease in the evaporation of moisture that controls summer rainfall, it observed. A decreased agricultural output and respiratory diseases too were attributed to the phenomenon. This UNEP report was based on an Indian Ocean Experiment (INDOEX) conducted between 1995 and 1999 by a team of 200 scientists.
The UNEP press release on this report was blamed for not reflecting the uncertainty of the phenomenon nor did it carry the note of caution that the report had contained. It had only sensationalized the findings. The Indian government slammed the UNEP position and the scientists of Indian Institute of Science challenged the description of wintertime haze over Asia as "brown cloud". As the initial focus of this science was South Asia the nomenclature of Asian Brown Cloud was seen as a conspiracy to shift blame for climate change to the southern world.
However, since then, several other such clouds have been studied across the world, including the US, Europe, India and China. This led to replacing of the nomenclature of Asian Brown Cloud with Atmospheric Brown Cloud.
This also reflects the complexity of the problem. While CO2 is distributed uniformly across the entire globe, black carbon pollution is more regional. Climate impact of black carbon has shown widely different impacts and also different trends in regional impacts. As black carbon has short atmospheric life it is expected to have higher impacts at the regional level-impacts on cloud formation, rainfall pattern and weather, snow melt and water systems. Depending on its composition it can also have both cooling and warming impacts on a regional scale. As these mostly travel short distances, their radiative forcing is regionally concentrated. They create hot spots and vary according to local conditions (see Graph: Global versus regional impacts).
Such widely different impacts make it difficult to have one comparative matrix. Scientists also point out towards the variability in impacts. In the northern hemisphere black carbon is likely to leading to early springtime snow melt but magnitude is uncertain. In South Asia absorbing particles may be influencing precipitation patterns. In Tibetan Plateau it may cause changes in circulation and darkening of snow and contributing towards glacier melting though the magnitude is not clear. All of them will require locally appropriate action.
Transboundary impacts will influence geo-politics
Local pollution also drifts across air sheds. This implies mitigation will require more regional approach. Most of these studies have been carried out in the US and Europe. Such studies have only begun to emerge in Asia.
In this regard the most investigated is the contribution of pollution from Asian countries that blows across Pacific Ocean to California or the West coast of the US. An extensive study has been initiated under the California Air Pollution Profiling Study (CAPPS). The US based Scripps Institution of Oceanography has carried out aircraft based studied. The modeling results show that as the altitude increases the fraction of the total BC that originates in Asia also increases. When pollution reaches the boundary layer it gets stable and travels long distances. At ground level black carbon that originates from Asia accounts for only 20 per cent of the total measured black carbon but at 3000 meters altitude the Asia black carbon accounts for 75 per cent of the total black carbon measured. This is very high over the west coast during the spring months. Pollution below boundary layer is more from local sources.