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Unformatted text preview: 1 Extraterrestrial Life: Spring 2008 Extraterrestrial Life: Lecture #7 Next homework: Thursday To frst approximation: distance From star and luminosity oF star determine the surFace temperature and possibility For liquid water on surFace Atmosphere (`greenhouse eFFect ) also plays an important role - warms Earth by ~20 degrees Celsius water vapor carbon dioxide methane increased concentration warms the planet Particulate matter (dust From volcanoes) cools Extraterrestrial Life: Spring 2008 Is the climate stable over geological time? eedback: iF the surFace temperature rises, does the concentration oF greenhouse gases in the atmosphere: increase, possibly raising the temperature Further? Positive Feedback decrease, oFFsetting the rise? Negative Feedback Empirically, expect negative Feedback to prevail on the Earth - but may be diFFerent For other planets Extraterrestrial Life: Spring 2008 Short term Feedback processes Short term Feedbacks are mostly positive - destabilizing e.g. water vapor: increased temperature leads to more evaporation From the oceans, increasing the atmospheric concentration oF water vapor Water is a greenhouse gas, so this is positive Feedback Role oF clouds?...
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- Spring '08