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Summary

Executive summary

Trans-national air quality issues are not a new phenomenon, but some contemporary air quality issues have the potential to have truly global impacts. One such issue is the deposition of black carbon, originating from fossil fuel combustion, onto snow and ice surfaces in the worlds mountainous glaciated regions. Black carbon lowers the surface reflectivity of snow and ice surfaces, thereby accelerating melt and reducing the capacity for new glacial ice to be formed. A substantial portion of the world’s population are dependent on snow and ice melt from snow and ice fields in the Himalaya and, given the geographical proximity to rapidly growing centres of industry and urbanisation and associated fossil fuel combustion, black carbon deposition is a growing issue, with levels increasing sharply since the 1990s in tandem with accelerated industrial growth in Asia. The same process of black carbon deposition may have accelerated snow and ice melt in the European Alps with the commencement and growth of the industrial revolution. 

In common with other glaciated regions, melt of Himalayan glaciers is accelerating and deposition of black carbon is further accelerating this melt, as well as affecting uplift within regional weather systems which has consequent impacts on precipitation delivery. In the short term, this accelerated melt yields ample water supplies, however in the medium to long term, yields of meltwater are likely to decrease. Considering how much food is exported globally from ‘breadbasket’ regions irrigated by Himalayan snow and ice melt, such as the Indo-Gangetic plain, any acceleration of snow and ice melt in the Himalaya will impact levels of irrigation waters to these agriculturally productive zones, upon which the global community is dependent; air quality issues in Asia thereby start to assume a global significance. Although there is little we can do to directly impact this issue from the UK, irrespective of where we are located, particulate emissions induce warming through absorption of energy and so our efforts to reduce them not only improves health in our local areas, but also helps rein in our much wider contribution to warming.