Lecture 3 Notes
Lecture 3 Notes Geo 002
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This 3 page Class Notes was uploaded by Linda Tan on Monday February 8, 2016. The Class Notes belongs to Geo 002 at University of California Riverside taught by Prof. Tim Lyons in Winter 2016. Since its upload, it has received 30 views. For similar materials see Earth's Climate Through Time in Geology at University of California Riverside.
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Date Created: 02/08/16
Geo 2 Lecture 3 Notes: The Global Energy Balance and Greenhouse Gas Effect Greenhouse Gasses are important Part of the reason Earth has liquid water. The right surface temperature kept by the amount of sunlight received and the greenhouse effect of the atmosphere (liquid water 0- 100 degrees Celsius). We are in the Goldilocks or habitable zone. Without greenhouse gasses the average surface temperature would be 30 degrees Celsius colder than it is now and earth would be icy and desolate Greenhouse gasses allow energy from the sunlight in, but does not allow energy to escape. Radiation from the Sun: ~50% visible light, ~40% infrared, ~10% UV (ozone can block UV rays, but depleting) Radiation from the Earth: Infrared radiation Note: We know the wavelength of the maximum flux of radiation emitted by an object depends I nversely on the object’s temperature. λ = 2898/T max The Sun emits energy from the photosphere at 5780 K, so λ max= 0.5 µm which is mostly visible light. But loses energy when it hits the earth’s surface and does not have enough energy to escape. It loses energy because the earth’s temperature is much cooler at 288 K The solar energy is absorbed and reflected by both the surface and the atmosphere The energy absorbed creates a warm cushion for the earth (steady state example) Ideally eventually the amount of energy received it released. In reality the budget is out of balance because of the increase in greenhouse gasses and the temperature of the earth will want to increase until a new (higher) steady state is achieved Earth’s Surface Temp depends on: 1. Solar Flux 2. Earth’s reflexivity (albedo) 3. Amount of warming provided by atmosphere (i.e., greenhouse effect) How greenhouse gasses work Like how a greenhouse works. The atmosphere is like the glass of a greenhouse. It lets light energy from the sun enter. Once the light hits a surface, it losses energy and is unable to escape making heat energy. By absorbing infrared radiation and reradiating some of it back toward the surface. Water vapor and Carbon Dioxide are less abundant gases that exert strong greenhouse effects. They have the ability to absorb and (re)emit infrared radiation. Different gases absorb efficiently at different wavelengths and this increases the importance of low concentration gases. The earth’s surface emits strongly in CO w2velength region making it a critical greenhouse gas. That is why most of the discussion about climate change is centered on CO 2 The amount and efficiency of greenhouse gases determines their importance. ie CO2and O 3 Note that this diagram is a positive feedback loop that includes atmospheric water vapor. Aerosols also contribute to the greenhouse effect by blocking incoming radiation and is being considered as a solution to climate change (climate engineering) Flux: amount of energy that passes through a unit area of atmosphere or intersects with unit area 2 of earth’s surface (eg engery/m ) The energy from the sun is distributed unevenly over the earth. Stronger at the equator and weaker at the poles. Each square meter of surface receives proportionately less energy as we move to higher latitudes. Which is DIFFERENTIAL HEATING At the poles outgoing energy > energy received and at the equator outgoing energy < energy received Net radiation: the difference between incoming and outgoing radiation According to what we know so far the tropics should be getting progressively warmer, while the poles progressively colder. But this doesn’t happen because latitudinal heating moves heat away from the equator. Half is moved by the ocean and half is moved by the atmosphere
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