lab 6

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Georgia State University *

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1112

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Geography

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Oct 30, 2023

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Q1: What things appear on the Sun to increase solar output and cause the solar constant to not be constant? Sunspots Q2: What objects/surfaces have the highest albedos? Clouds, Snow and ice, and the desert Q3: What surfaces have the lowest albedos? Oceans, forests, the savannah Q4: What type of feedback mechanism involves the melting of sea ice which then results in more absorption of solar radiation than the ice did and thus results in the further melting of ice? Hint: Watch the video. The ice albedo feedback mechanism Q5: What type of radiation is absorbed and emitted by gases as part of the greenhouse effect? Thermal infrared radiation Q6: Which greenhouse gas had the largest radiative forcing from 1750 to 2011? CO2 and CH4 Q7: What is the source of the 341 W m -2 of radiation that is entering the Earth- atmosphere system? incoming solar radiation from the Sun Q8: What gas is responsible for much of the 78 W m -2 that is absorbed by the atmosphere? This gas had a leading role in Lab 2. CO2 because it has a higher radiative forcing, although having a lower radiative efficiency than CH4.

Q9: What gases cause the “back radiation” and what type of radiation is it? The gases that cause the “back radiation” are N2O, CO2, AND CH4. This type of radiation is called infrared radiation Q10: What is the solar constant for Earth that is used throughout this exercise? Please provide the units. 1365 W m-2. Q11: What is Earth’s albedo when Earth is portrayed as a black body without an atmosphere? The Earth's albedo is zero when Earth is portrayed as a black body without an atmosphere. Q12: What is the only control of Earth’s surface temperature when Earth is portrayed as a black body without an atmosphere? Remember that the main controls of Earth’s surface temperature are incoming solar radiation (i.e., solar constant), albedo of the Earth, and the greenhouse effect. the solar constant Q13: What is the actual albedo of Earth’s surface? The actual albedo of Earth's surface is 0.13W m-2 Q14: How do you think adding a surface albedo to Earth will affect the global surface temperature (i.e., how will the temperature change when going from a black body to Earth with surface features)? adding a surface albedo to Earth will affect the global surface temperature by decreasing it. Q15: How and why did Earth’s surface temperature change when going from being a black body to being a planet with surface features (e.g., water, forest, deserts, and snow & ice)? The Earth's surface temperature changed when going from being a black body to being a planet with surface features because of the total albedo of surface features

such as forests, deserts, water, snow and ice. These features reflect solar radiation, which decreased Earth's surface temperature. Q16: Why is it impossible to have surface features, such as water, forests, and snow & ice, and not have an atmosphere? Think of the hydrologic cycle (Lab 3) and the carbon cycle (Lab 4). It is impossible to have surface features such as water, forests, snow and ice and not have an atmosphere because our surface features cannot sustain themselves without the atmosphere. The hydrologic cycle provides water to plants in forests and precipitation from the cycle can produce rain, snow, and sleet/hail (ice). The carbon cycle, which is essential to life, moves carbon throughout the world between Earth and the atmosphere which is vital for forests. Without either of these cycles, these surface features would not exist Q17: What is Earth’s albedo (i.e., what proportion of the incoming solar radiation is reflected by Earth’s atmosphere and surface)? The Earth's albedo is 0.30 W m-2 Q18: Taking into account both the change in albedo and the addition of the greenhouse effect, what effect do you think adding an atmosphere to Earth will have on its surface temperature? I believe that adding an atmosphere to Earth will have an increase in the surface temperature Q19: Even with a large increase in albedo, why is current Earth nearly 20° C warmer than Earth with only surface features? the Greenhouse effect. Q20: How did land cover during the Last Glacial Maximum differ from the current land cover? The four land cover types used in this section of the lab are water, forest, desert, and snow/ice. Land cover during the Last Glacial Maximum differs from the current land cover in that the Last glacial Maximum had increasingly more land cover than the current land cover. The icesheets during the Last Glacial Maximum cover a great portion

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of land as well as ocean. Whereas the current land cover is minimum and mostly in the ocean. Q21: What was your estimate of Earth’s albedo during the Last Glacial Maximum? Why should it be larger than the Earth’s current albedo of 0.30? 68. It should be larger than the current albedo because the Last Glacial Maximum the surface features are covered in sheets of ice. The snow and ice have a high albedo and the high amount of snow and ice increases the overall albedo of the Last Glacial Maximum Q22: How much cooler do you think Earth was during the Last Glacial Maximum compared to the current temperature? I believe the Earth was much colder during the Last Glacial Maximum compared to the current temperature. As you can see from the aerial shots, the ice sheets during the Last Glacial Maximum were much larger and covered more land than current day. This is because the surface temperature was colder and could keep ice sheets and snow cold enough not to melt on contact to the ground. Q23: How much colder was Earth’s surface temperature during the Last Glacial Maximum compared to the current temperature? The Earth's surface temperature during the Last Glacial Maximum was approximately 8degrees colder than the current temperature. The Last Glacial Maximum surface temperature was52.1 degrees Fahrenheit. While the current surface temperature is 60.3 degrees Fahrenheit Q24: Why did the lower temperatures result in lower atmospheric CO 2 concentrations? Think back to Lab 4 about the carbon cycle and what component of the cycle was taking in more CO 2 during the Last Glacial Maximum. The large amount of sheet ice caused the lower temperatures which resulted in lower atmospheric CO2 concentrations Q25: What impact did a lower CO 2 concentration have on the greenhouse effect and ultimately Earth’s surface temperature?

The lower CO2 concentration had a negative effect on the greenhouse effect in that less greenhouse gases mean less global warming. This ultimately also made the Earth's surface temperature cooler Q26: What is the projected atmospheric CO 2 concentration in 2050 and why are CO 2 concentrations projected to increase? The projected atmospheric CO2 concentration in 2050 in 510 ppm. CO2 concentrations are projected to increase because of fossil fuel emissions from humans. Q27: What do you expect the global surface temperature to be in 2050 and how much different will it be from the current temperature? I think the global surface temperature in 2050 will be different from the current temperature in that it will increase exponentially. Unless humans make a complete switch to green energy I believe the Earth's surface temperature will continue to rise Q28: How much global warming is expected between now and 2050 and what is the major factor behind the warming? The amount of global warming expected between now and 2050 is a 2.6 degree increase in surface temperature. The major factor behind this instance of global warming is because the co2concentration more than doubled since 2020 Q29: List one assumption you made when modeling Earth’s surface temperature? An assumption that I made was that as CO2 concentrations increase, surface temperature does as well. How does a change in the solar constant impact the absorption of shortwave radiation and the emission of longwave radiation by the Earth-atmosphere system?

How does the ocean impact Earth’s energy balance? How does the concentration of greenhouse gases, besides water vapor, impact Earth’s surface temperature? An increased solar constant will lead to increased absorption of solar radiation and in turn a decreased emissions of longwave radiation by the Earth-Atmosphere system. The ocean absorbs most of the solar energy reaching the Earth. As the Equator receives much more solar energy than do the Poles, enormous horizontal and vertical ocean currents form and circulate this heat around the planet. Earth's temperature rises in response to increased greenhouse gases.

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