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UNC-Chapel Hill GEOG 111 - Climate Change

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GEOG 111 1st Edition Lecture 9 Outline of Last Lecture I. Energy Imbalances and Energy TransferII. Greenhouse effecta. The Carbon CycleOutline of Current Lecture I. Temperature TrendsII. Complexities of climate changeCurrent LectureI. Temperature trendsa. Climate variability- the temperature departures above or below a long-term average value (from one year or one decade to the next)i. Temperature anomalies March 2012: extremely unusual for NC weather compared to March 2013: much colder1. Illustrates that there’s a lot of natural variability that can’t necessarily beattributed to climate change or greenhouse gasesb. Climate change- continuous change over a long time period (much longer than climate variability)i. There’s a large amount of temperature variability and change in our atmosphere1. Uncertain as to how much warmer the climate will be in the futureII. The complexities of climate changea. Challenges of estimating earth’s temperaturei. Take temperature trends from weather stations across the Earth and average themii. Stations can have biases1. Station density: amount of people in the areaa. Thermometers are located at airports in urban societies (which are much warmer)2. Oceans: very few observations are taken from the oceans which cover a huge percentage of Earth’s surfaceiii. Those stations with biases are removed from the average which leaves few stationsb. Earth-atmosphere is a complex system: not as simple as adding greenhouse gases and warmingi. Consider systems attributesii. Feedbacks1. Positive feedbacks- things happen in the system to cause it to warm up moreThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.a. Ice-albedo feedback mechanism- GH gases  warming  ice caps melt (aerial extent of the ice decreases)  slightly lower albedo  more energy is absorbed and the area warmsb. Cracks/fissures in the ice sheet melting process- accelerates ice melting process as water flows through the fissuresc. This mechanism is working because high latitude areas are warming more than low latitude areasd. In addition… GH gases  warming  more evaporation  more water vapor (which is a greenhouse gas)2. Negative feedbacks- something happens in the system that slightly coolsthe environment back downa. GH gases  warming  more evaporation  more clouds  higher albedo (more light reflected)b. On a longer time scale: GH gases  warming  more organisms/photosynthesis  less CO2 (because it’s taken up by marine and terrestrial life)iii. Nestedness1. Smaller systems within the macroa. Example: warmer air moves up into the atmosphere redistributing the warmth (convection) produces more clouds (water vapor)b. The influence of clouds: depends on the nature of the cloud: high level/thin clouds (cirrus) only reflect a small amount but are effective in absorbing longwave radiation; increases of low level/thick clouds (cumulus) result in more cooling2. System thresholds and statesa. Is the climate change associated with greenhouse warming gradual or abrupt?b. Analogous to pushing a ball up a hill; climate increases slowly but then may abruptly


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