side. The Kali Gandaki Valley is a very open connection to the Tibetan Plateau; this could be a major route of transport of aerosols to the plateau and the glaciers.

What Do We Know About Snow-Darkening
Effects on Himalayan Glaciers?

Teppei J. Yasunari, NASA Goddard Space Flight Center

Absorbing aerosols such as dust, black carbon, and organic carbon are well-known warming factors in the atmosphere. When aerosols deposit on snow, it causes darkening of snow, causing absorption of more energy at the surface, leading to accelerated melting of snow. If this happens to Himalayan glacier surfaces, the melting may contribute to mass balance changes, though the mass balance itself is a complicated issue. There are limited observations of the effect of snow darkening on glaciers, but most of our knowledge is the result of model simulations. Ice-core measurements of black carbon show much higher concentrations in recent years (1995-present). However, since 1860, there has not been an overall trend of an increase in dust. Black carbon satellite data over the region is still limited, and most of the snow samples measuring black carbon are from the eastern side of the region (e.g., in China). These snow samples show “rings” of very clear deposition that can help track levels of black carbon and dust. The black layers correspond to the spring season (when the atmospheric concentration of black carbon is higher). Though such studies show an increasing trend, we must be careful to integrate measurements to account for seasonality The NASA GEOS-5 model simulations show very large deposition of black carbon in the Himalayan snowpack—much larger than anywhere else in the world. Some studies suggest that this has significantly affected the albedo of the snowpack. This seems to correlate to studies that are showing increases in snow surface temperature and decreases in the snow water equivalent.

Hydroclimate Variability and Change over the
Northern Gangetic Plain and Himalayan Region

Sumant Nigam, University of Maryland, College Park

Analysis of the 20th century observational record can yield insights about future variability and change in the region. Models are not yet able to cover the regional hydroclimate, but the observational record itself has a lot of information that has not been sufficiently mined. AR4 simulations show that various climate products do not agree with each other (or the observations) regarding local trends. As such, there is a widely divergent agreement on projection models. Models can only produce the very broad features of climate and cannot resolve the specifics. However, this does not mean that the climate system cannot be resolved for the natural and secular impacts. Regressions of principal large-scale climate events, such as El Niño and monsoon, over the last century can show robust trends that can be used to reconstruct variables of interest (e.g., temperature and precipitation). Surface temperature is only captured broadly, and a latitudinal increase is observed in the region. If the natural variability can be unraveled from secular change components, analysis of the 20th century observational record could yield insights about future variability and change. There are several techniques to tease out the actual physical components from larger variability. For example, one can look at trends using observations for the full 20th century and the last 60 years. The 60-year trends show decadal variability most likely coming from the El Niño-Southern Oscillation. The century-long trend analysis does not show these trends.

Hydroclimatic Challenges for Pakistan:
Ideational and Material Drivers

Daanish Mustafa, King’s College London

Water has multiple values in all cultures beyond its obvious use for livelihoods and economic value generation. Most modern water management systems in the world tend to be indifferent to the multiple, cultural, spiritual, aesthetic, and identity values that are nevertheless important to water users. There is considerable uncertainty regarding specific climate scenarios at the country scale; but it is certain that past climatic normals will not continue into the future. Climate change for Pakistan, as in the rest of the world, will involve decisions on water management in a context in which past trends are no longer effective guides for future action. Pakistan in particular has suffered some dramatic and unusual hazards over the past decade, ranging from



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