GEOG 111 1st Edition Lecture 9 Outline of Last Lecture I Energy Imbalances and Energy Transfer II Greenhouse effect a The Carbon Cycle Outline of Current Lecture I Temperature Trends II Complexities of climate change Current Lecture I Temperature trends a 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 colder 1 Illustrates that there s a lot of natural variability that can t necessarily be attributed to climate change or greenhouse gases b 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 atmosphere 1 Uncertain as to how much warmer the climate will be in the future II The complexities of climate change a Challenges of estimating earth s temperature i Take temperature trends from weather stations across the Earth and average them ii Stations can have biases 1 Station density amount of people in the area a 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 surface iii Those stations with biases are removed from the average which leaves few stations b Earth atmosphere is a complex system not as simple as adding greenhouse gases and warming i Consider systems attributes ii Feedbacks 1 Positive feedbacks things happen in the system to cause it to warm up more These 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 warms b Cracks fissures in the ice sheet melting process accelerates ice melting process as water flows through the fissures c This mechanism is working because high latitude areas are warming more than low latitude areas d 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 cools the environment back down a 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 Nestedness 1 Smaller systems within the macro a 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 cooling 2 System thresholds and states a 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 decrease
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