Four simulations of the surface mass balance (SMB) of the Greenland ice sheet (GrIS) are compared over the period 1960–2008. Total SMB estimates for the GrIS are in agreement within 34% of the four model average when a common ice sheet mask is used. When models' native land/ice/sea masks are used this spread increases to 57%. Variation in the spread of components of SMB from their mean: runoff 42% (29% native masks), precipitation 20% (24% native masks), melt 38% (74% native masks), refreeze 83% (142% native masks) show, with the exception of refreeze, a similar level of agreement once a common mask is used. Previously noted differences in the models' estimates are partially explained by ice sheet mask differences. Regionally there is less agreement, suggesting spatially compensating errors improve the integrated estimates. <br><br> Modelled SMB estimates are compared with in situ observations from the accumulation and ablation areas. Agreement is higher in the accumulation area than the ablation area suggesting relatively high uncertainty in the estimation of ablation processes. Since the mid-1990s each model estimates a decreasing annual SMB. A similar period of decreasing SMB is also estimated for the period 1960–1972. The earlier decrease is due to reduced precipitation with runoff remaining unchanged, however, the recent decrease is associated with increased precipitation, now more than compensated for by increased melt driven runoff. Additionally, in three of the four models the equilibrium line altitude has risen since the mid-1990s, reducing the accumulation area at a rate of approximately 60 000 km<sup>2</sup> per decade due to increased melting. Improving process representation requires further study but the use of a single accurate ice sheet mask is a logical way to reduce uncertainty among models
Architecture, landscape architecture and urban design are seldom merely benign aesthetic propositions. With its victory in the Spanish-American War (1898), the United States unexpectedly found itself in possession of an empire. Within a volcanic climate of patriotic fervour, Washington's new imperial status galvanized interest in improving the city in a manner commensurate with its enlarged role. On the strength of his work at the World's Columbian Exposition (1893), celebrated architect Daniel Hudson Burnham took the lead in Washington's transformation (1901-2) and urban design became his medium for imperialist expression. This potent mechanism's deployment would not be confined to the imperial hearth. The United States soon set its sights on modernizing, that is 'Americanizing', Manila, the antique capital of its newly-acquired Philippine colony, and similarly charged Burnham with the task (1904). Overtly emulating the British Raj in India, he was also to design a wholly new summer capital there. This essay canvasses Burnham's work at the American and Philippine capitals, along with his vicarious hand in the design of a new model American town in the Panama Canal Zone, considering it through the lens of imperialism. The location and imperial purpose of these projects also reminds us that -at least from an antipodean perspective -in the early 20th century, Great Britain held no monopoly on empire.
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