Mitigation: the built environment and climate change
Provided by Brian Edwards: Emeritus Professor of Architecture Edinburgh College of Art and Associate Professor of Sustainable Architecture, Royal Danish Academy of Fine Arts.
A distinction can be made between ‘mitigation’ and ‘adaptation’. The first deals with the impact the built environment has upon climate change and the second (adaptation) with how we need to change our design practices to adapt to a warming world. Mitigation is necessary because roughly a half of man-made carbon emissions result from buildings and when you include transport to reach them, the figure approaches 75%.
Heating, lighting, cooling and ventilation of buildings accounts for around 40% of global carbon emissions. The embodied energy needed to construct buildings accounts for another 5-10%. So architecture is critical to the carbon debate. Since carbon emissions are measured in CO2, and since this is the main greenhouse gas leading to global warming, architects carry a particular responsibility.
Mechanisms of climate change. (Click image to enlarge)
Greenhouse gases consist mainly of carbon dioxide (CO2) and methane (CH4). Carbon dioxide is the result of burning carbon based fuels (oil, gas, coal, timber) whilst methane occurs mainly as a result of decomposition. Architects are implicated in methane to a lesser degree but methane is waste generated and waste is often the result of poor construction and habitation.
The term ‘greenhouse gases’ refers to a cocktail of human emissions which sit in the upper atmosphere. Some are stable and long-lived such as CO2, others are more transient such as methane. Methane has a half life of seven years but is about seventy times more potent than carbon dioxide. Fortunately it only represents a small proportion of greenhouse gases; the bulk by far being CO2. The ring of green gases prevents radiant energy from the Sun being redirected back into space after striking the Earth- hence it works like glass or plastic in a greenhouse. Predictions vary but global temperatures are expected to rise by between 1.8 and 4 degrees centigrade over the current century.
Carbon is the current focus because it can measured, traded (through the Emissions Trading Scheme) and regulated (through Kyoto agreements). In fact, societal debate is moving from an energy one to a carbon one. This is because we are generating an increasing amount of energy from the Sun, wind and geothermal sources. Energy is not the problem but carbon is.
Potential climate change impacts. (Click image to enlarge)
Politicians are currently trying to limit global temperature rise by 2 degrees. This is because climate scientists predict an escalation in the rise above this level as a result of the expansion of oceans coupled with deforestation and increased desertification. There are natural cycles of climate change but man’s contribution to destabilizing natural systems through burning ever more carbon based fuels is high up on inter-governmental agendas.
One of the key drivers of debate and policy is the UN. It convened important conferences such as at Rio (1992) and Kyoto (1997). Besides setting binding targets for CO2 emissions, the UN helped coin and define the term ‘Sustainable Development’. Although the USA and China remain outside present agreements, there are signs that their investment in alternative energy technologies may achieve more than international laws. The EU is also active in legislating for energy standards and has introduced a Europe wide scheme of energy labeling extending from washing machines to cars and buildings.