Observed high-altitude warming and snow cover retreat over Tibet and the Himalayas enhanced by black carbon aerosols

TitleObserved high-altitude warming and snow cover retreat over Tibet and the Himalayas enhanced by black carbon aerosols
Publication TypeJournal Article
Year of Publication2016
AuthorsXu Y, Ramanathan V, Washington W.M
JournalAtmospheric Chemistry and Physics
Volume16
Pagination1303-1315
Date Published2016/03
Type of ArticleArticle
ISBN Number1680-7316
Accession NumberWOS:000371284100007
Keywordsalbedo; community atmosphere model; cycle; deposition; hydrological; ice; impact; plateau; regional climate simulations; solar absorption; temperature
Abstract

Himalayan mountain glaciers and the snowpack over the Tibetan Plateau provide the headwater of several major rivers in Asia. In situ observations of snow cover extent since the 1960s suggest that the snowpack in the region have retreated significantly, accompanied by a surface warming of 2-2.5 degrees C observed over the peak altitudes (5000 m). Using a high-resolution ocean-atmosphere global climate model and an observationally constrained black carbon (BC) aerosol forcing, we attribute the observed altitude dependence of the warming trends as well as the spatial pattern of reductions in snow depths and snow cover extent to various anthropogenic factors. At the Tibetan Plateau altitudes, the increase in atmospheric CO2 concentration exerted a warming of 1.7 degrees C, BC 1.3 degrees C where as cooling aerosols cause about 0.7 degrees C cooling, bringing the net simulated warming consistent with the anomalously large observed warming. We therefore conclude that BC together with CO2 has contributed to the snow retreat trends. In particular, BC increase is the major factor in the strong elevation dependence of the observed surface warming. The atmospheric warming by BC as well as its surface darkening of snow is coupled with the positive snow albedo feedbacks to account for the disproportionately large role of BC in high-elevation regions. These findings reveal that BC impact needs to be properly accounted for in future regional climate projections, in particular on high-altitude cryosphere.

DOI10.5194/acp-16-1303-2016
Short TitleAtmos. Chem. Phys.
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