CU1_HW_ANSWERS_Spring2022

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Columbia University *

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Geography

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Oct 30, 2023

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1 Homework Questions for Climate and Us Week 1 Due the week of April 18 ANSWER KEY 1. Factors affecting Earth’s climate In lecture this week, Prof. McManus discusses the various factors that influence Earth’s climate. Consider what you learned in lecture to answer the following questions. A. Which of the following statements is/are true about Earth’s climate system? Select all that apply. a. Climate involves interactions with the ocean, the atmosphere, and the biosphere. b. El Niño-Southern Oscillation (ENSO) is an example of a climate phenomenon that has global impacts. c. Climate includes multiple factors, such as temperature and precipitation. d. Atmospheric circulation impacts Earth’s climate, but ocean circulation does not. a), b), and c) are correct answers. d) is incorrect because atmospheric AND oceanic circulation impact regional climate as both involve the redistribution of heat and energy across the globe. B. Which of the following statement(s) is/are true regarding factors that influence Earth’s temperature? Select all that apply. a. A higher number of sunspots decreases the amount of solar energy reaching the Earth’s surface, resulting in cooler temperatures. b. Large increases in albedo lead to warmer temperatures, as we have witnessed in recent decades. c. Greenhouse gases reflect incoming solar radiation, thus changing Earth’s temperature. d. Greenhouse gases absorb outgoing infrared radiation, thus changing Earth’s temperature. e. Greenhouse gases in the atmosphere increase the temperature of the Earth. d) and e) are the correct answers. a) is incorrect because a higher number of sunspots is a proxy for higher solar activity, which will lead to a greater amount of solar energy reaching the Earth’s surface and a small increase in temperatures on Earth . b) is incorrect because an increase in albedo would suggest more reflectance and cooler temperatures. c) is incorrect because greenhouse gases are transparent to incoming solar radiation, but absorb/re-emit outgoing infrared (longwave) radiation.

2 C. As you learned in lecture, the Earth currently has an albedo (or total reflectivity) of about 30%. Imagine a dystopian future where almost all of the glaciers and ice sheets on the planet have been replaced by dark, asphalt shopping mall parking lots. Assuming that only albedo changes and all of the other factors that influence climate on Earth remain constant, how would you expect Earth’s temperature to change relative to today? a. Temperature would be lower because Earth becomes more reflective. b. Temperature would be higher because Earth becomes less reflective. c. Temperature would be higher because Earth becomes more reflective. d. Temperature would be lower because Earth becomes less reflective. b) is the correct answer. The darker colored asphalt parking lots will result in less reflectivity at the Earth’s surface and therefore more absorption of radiation, increasing the temperature of the Earth. 2. Earth’s Energy Balance Any given planet’s climate is determined by an energy balance. Earth’s energy bal ance is such that it creates a livable environment for humans and other life, unlike those of nearby Venus or Mars. Climate forcings are factors that drive changes in climate and alter the Earth’s energy Balance. Use Figure 1 (below) to answer the following questions. Figure 1. Energy balance diagram showing the flow of energy (in Watts per square meter, or W/m 2 ) from the sun, Earth’s surface, and through the atmosphere. Yellow regions show incoming solar (shortwave) radiation. Red regions show outgoing infrared (longwave) radiation.

3 A. TRUE OR FALSE (correct the statement if false): This diagram represents a balance between incoming and outgoing energy. TRUE B. What three values illustrate the balance between incoming and outgoing energy? a. Incoming solar radiation + radiation absorbed by the surface = outgoing longwave radiation b. Radiation emitted by the atmosphere + surface radiation = outgoing longwave radiation c. Incoming solar radiation – reflected solar radiation = outgoing longwave radiation d. Incoming solar radiation – radiation absorbed by the atmosphere = outgoing longwave radiation c) is correct. Incoming solar radiation (342 W/m 2 ) - reflected solar radiation (107 W/m 2 ) = outgoing longwave radiation (235 W/m 2 ). C. TRUE OR FALSE (correct the statement if false): Greenhouse gases largely absorb incoming solar (shortwave) radiation. FALSE. Greenhouse gases largely absorb outgoing longwave (infrared) radiation. OR FALSE. Greenhouse gases do not absorb incoming solar (shortwave) radiation. Extra note: The only greenhouse gas that does significantly absorb in the shortwave (solar) part of the electromagnetic spectrum is ozone, which is why it is such an important component of our atmosphere that protects against excessive solar radiation. D. If the amount of energy reflected by the Earth’s surface decreases due to melting snow and ice cover, which of the following will be true? Select all that apply a. The amount of solar radiation absorbed by the Earth’s surface will increase b. The amount of solar radiation reflected by the Earth’s surface will increase c. The amount of solar radiation absorbed by the Earth’s surface will decrease d. The amount of solar radiation reflected by the Earth’s surface will decrease a) and d) are correct answers. With less snow and ice cover, the amount of solar radiation reflected by the Earth’s surface will decrease and so the amount absorbed by the Earth’s surface will increase. This contributes to the overall increase in global average temperature. 3. Recent Climate Change and Impacts Figure 2 (next page) shows measurements of atmospheric CO 2 from the Mauna Loa Observatory station collected by the ALOHA station off the coast of the Hawaiian island O’ahu (see inset map) starting in 1958. Seawater pH has also been measured at station ALOHA since approximately 1990, as shown in Figure 2.

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