Transformation of Urban and Natural Landscape

Earth is currently transitioning from a mostly rural to a mostly urban planet. In 2030 the urbanized areas will be nearly tripled compared to 2000 (Seto et al. 2012). The use of dark building materials, such as asphalt and concrete, leads to a lower albedo in urbanized areas than in natural environment (Brest 1987). It negatively affects climate and it might be more relevant in the near future. The substitution of rooftops’ membranes and pavements’ traditional materials with bright ones and a wise planning of the future urban sprawl can remedy the low urban albedo. Here we investigate the potential effect of the increase in albedo on the instantaneous change in radiative forcing in a sample of European cities. We find a distinct but surprising geographical variation of the potential. With Scandinavian cities being potentially more effective that north-central European ones. Our results highlight that the increase in albedo in European cities can contribute to reduce instantaneous radiative forcing (IRF) at the top of the atmosphere (TOA) mostly depending on urban morphology.

The IPCC Working Group I Fourth Assessment Report reports that since pre-industrial times until 2005, Land Use and Land Cover Change (LULCC) led to a decrease in RF of 0.2 [± 0.2] W m-2 due to an increase in Earth’s albedo (Salomon et al. 2007). The magnitude of the LULCC-induced decrease in RF is comparable to the effect of some anthropogenic long-lived greenhouse gases in the atmosphere (e.g., nitrous oxide). The increase in Earth’s albedo is mainly ascribable to deforestation and modification of land for agricultural use (Foster et al. 2007). However, the effect of the LULCC on RF embodies the contribution of urbanization since it is not trivial to isolate...

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