NY Urban

Global dimming is said to be one of the most prominent examples indicative of athropogenic disturbances. This phenomenon is mostly dominant in large urban sites as studies have shown that large cities with a population greater than 0.1 million, when compared to sparsely populated sites, are in general steady sources of anthropogenic pollutants like fossil fuels, nitrates, sulfates, and soot (Alpert, 2005). The paper by Alpert (2005) aims to investigate if global dimming is a local or global phenomenon.

However, I feel that urban development produces other effects too that can contribute to the changes in solar radiation and it is not solely the fault of anthropogenic aerosols. Some examples include the urban heat island effect, deforestation, and changes in surface albedo. Moreover, people tend to settle near coastal areas which further contribute to the uncertainty of the study.

(3) rural vs urban pop

Figure 1. (World Urbanization Prospects, 2014)

The above figure demonstrates the varying levels of urbanization across regions. Nevertheless, they have one thing in common and that is that the urban population is increasing. Over the decades, the level of urbanization is expected to increase in all regions with Africa and Asia doing so at a faster rate than the rest.

Hence, in my opinion, it is not so much an issue of whether global dimming is a global or local phenomenon because with most parts of the world catching up with the trend on urbanization, it will soon be a global concern.


Alpert, P. (2005). Global dimming or local dimming?: Effect of urbanization on sunlight availability. Geophysical Research Letters32(17).

World Urbanization Prospects. (2014). World Urbanization Prospects, the 2014 revision. Retrieved 23 January 2015, from http://esa.un.org/unpd/wup/Highlights/WUP2014-Highlights.pdf