Page 029 - Sensor § Which raises the
Source section: Section 2 - Sustainable Thinking PDF page: 29 Guide page: 22 OCR quality: high (298 words)
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Sensor § Which raises the temperature and melts more’snow we o P Fewer surfaces ¢ remain covered : 3 . o with snow 9? 0098 © 5 As tl earth oe When snow melts, 9etS warmer ~ zs . the darker surfaces Stimulus Counteraction absorb more heat Figure 2.1. Negative Feedback Loop Figure 2.2. Positive Feedback Loop POSITIVE FEEDBACK LOOPS, on the other hand, are self-reinforcing: the stimulus causes an effect, and the effect produces even more of that same effect. Population growth is a positive feedback loop. The more babies who are born, the more people there will be in the population to have more babies. Therefore, the population can be expected to rise until acted upon by another force, such as an epidemic or shortage of resources. In the built environment, roads and infrastructure built out to the urban fringe often result in a positive feedback loop of increased development. This suburban growth can sprawl far from the urban core, requiring more roads and encouraging additional growth, as well as using more resources (energy, water, sewage systems, materials) to support that growth. Climate change is another positive feedback loop. As the earth gets warmer, fewer surfaces remain covered with snow, a reflective surface that bounces incoming heat from the sun back into space. When snow melts, the darker surfaces absorb more heat, which raises the temperature and melts more snow. Similarly, in the built environment, the dark surfaces of roofs, roads, and parking lots absorb more heat from the sun. This z heat island effect raises temperatures in urban areas several degrees above the temperature of surrounding E areas, increasing the demand for cooling and the amount of energy that buildings use. The additional energy a , -_ ‘ : ‘ <3 u use can increase carbon emissions, which contribute to global warming, further raising urban temperatures a x and energy use, and the cycle continues.
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