An Urban Climate Model for Use in Strategic Environmental Assessment - Case: Creating a Climate Change Resilient Ng’ambo, Zanzibar City

Abstract

The urban climate has become a vital consideration for many populations as the effects of climate change are becoming increasingly prevalent. The climate in cities is different compared to rural areas, not least because of the minimal vegetation and the characteristics of building materials. As cities are getting hotter and heat-related mortality is increasing, eyes of urban planners and politicians are turning towards the necessity of climate change adaptation. The responses turned to often involve downscaling climate change projections to cover the local climate in order to have a basis for local adaptation strategies. However, within the scientific field of urban climatology, the differences between urban and rural temperatures have been documented and observed for over 100 years. The use of this knowledge could lead to more effective and site-specific climate change adaptation measures in city planning. To effectively integrate urban climatology into adaptation strategies it needs to be addressed at an early stage. An available methodology that could embrace these issues is for example Strategic Environmental Assessment (SEA), an internationally accepted and standardized tool which is adaptable to a broad variety of contexts. Developing countries are more vulnerable to, and also face the highest projections of, climate change. Here adaptation measures are needed that are economically, socially and environmentally justifiable whether projected climate hazards occur or not. Again, SEA might prove to be a viable tool for finding these low-key adaptation measures. This study does not perform an SEA, but borrows its methodology and structure in a case study performed on the archipelago of Zanzibar. Within this methodology an easy-accessible urban climate model is used which makes the expertise of urban climatology available to urban planners and non-climate-experts. The study shows that increased vegetation and water, together with reduced building density and mass, can cause significant temperature reductions in urban areas. These differences are actually larger than the expected temperature increases due to global warming. Even though a simple model is used and the results need to be more thoroughly verified, the outputs can provide rough guidance early in a planning process. The main recommendation reached in the case study include ensuring a surface cover composition that encompasses a high degree of vegetation. Further it is recommended to consider building mass and density and finally to give the climatic properties of buildings materials some thought.