The Grey Twilight, by Léa Silvestrucci
Please find below the updates on Léa’s research into the effects of global dimming and the human relationships to the sun.
First recognised in 1950, the global dimming effect is an observation of the reduction of the amount of solar radiations reaching the surface of the Earth. The release of particules resulting from human activities in the atmosphere is the origin of this phenomenon. Once these particules are in the atmosphere, they absorb and reflect radiation before they can reach the surface of the planet.
When learning about this effect, some questions emerged: what would a world with much less sunlight look like? How would we, as humans, react to it? How far would we be ready to go to channel, redirect and maybe even capture sunlight? Global Dimming aims to explore these questions, their limits and their possibilities.
Simply put, global dimming is a complex phenomenon that is the result of the interconnection of humans and the environment. In this case, humans have a negative impact on the environment who in turn has a negative impact on humans, who then have a negative impact on the environment, and so on. It is a vicious circle.
One of the challenge of working on such a subject is to try to make sense of the complexity of it and to break it down into more ‘digestible’ parts. The above illustrations are an attempt to visually represent different elements, centred around sunlight, of global dimming. These elements are: the relation between humans and the environment previously described, the mechanism of global dimming impacting sunlight, and how the interaction between brown clouds and sunlight works.
Clouds are classified in three main categories based on their altitude. The categories are: low-level clouds which are below 2km; mid-level clouds, between 2 and 7km; and high-level clouds between 5 and 13km.
Brown clouds, which are responsible for the absorption of solar radiations, are low to mid-level clouds. They can be found from the earth surface to up to 3km. There are two types of these clouds: urban brown clouds, found above cities, and atmospheric brown clouds, a regional phenomena that can, for example, be observed over South Asia and the northern Indian Ocean. This type of cloud is made of black carbon, fly ash and soil dust, which give it its brown colour.
Another type of clouds play a part in global dimming: bright white clouds that can be found over oceans and seas which are called ship tracks. These clouds are made of sulfite particules and water vapour, and are produced by ships. They are comparable to contrail. Due to their brightness they reflect sunlight back to space and so block it from reaching the surface of the earth.
When thinking of global dimming and how it can, as a concept, be magnified to be made more relatable and tangible, one question emerged: what would a city with less sunlight look like, and how would people adapt to it?
A first approach to answering this question has been to find a space that reproduces the conditions of what this magnified global dimming could be. Thus, the vastness of the city was been reduced to a single room. A north-facing bedroom with a single-window and no sunlight entering it. The perfect exacerbation of what global dimming could be and could feel like.
The above photos show some explorations and attempts at redirecting, channeling, and projecting sunlight with different reflective surfaces to break the darkness of the room.
Since we, humans, began burning coal, and other fossil fuels, during the Industrial Revolution two centuries ago, the sea level has been rising. Over the period of the 20th century, the rise was roughly of 17cm. Since 2000 there has been an acceleration of the rate at which the level of the sea is rising, with a global increase of 6cm in just the past twenty years. If nothing is done to control this acceleration, to put a stop to this business as usual scenario, it is predicted that the global sea level will rise around 1.5 meter above the current level, in the next fifty years. 
What will a rise of 1.5 meter of the sea level look like in London? This question is what prompt the creation of the two above images. The first shows a selection of landmarks, in the city, that will be submerged.  The second explores the change to the shape of the path the Thames follows, with the current one in green, and the predicted one for 2070, in white. 
 3D images taken from Google Maps
Climate and Cities is a collective
which investigates the interactions
of climate and cities through
creative research and projects.
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