Earth Science ALBEDO LAB INVESTIGATION Driving Question: What effect does albedo have on surface temperature? Background Earth’s albedo is the fraction of incoming radiation (sunlight) that is reflected into space. The Earth has an average albedo, which describes how much sunlight is reflected on average for the whole planet and the whole year. That value is about 0.3. The Earth also has a local albedo, which determines how much of the Sun’s light is reflected from a particular place at a particular time. The local albedo depends on the particular local surface, which can change seasonally as vegetation changes. It also depends on more rapidly changing things such as snow and clouds. For reference, the values of albedo range from 0.0 to 1.0, where a value of 0.0 is for a surface that absorbs all radiation (reflects 0 percent) that strikes its surface, and a value of 1.0 represents a surface that reflects 100 percent of the radiation that strikes it. § Fresh snow has an albedo ranging from 0.75 to 0.90. § Dry dark soil has an albedo of approximately 0.13. § Open ocean has an albedo of approximately 0.10. How fast the planet warms in response to adding greenhouse gases to the atmosphere depends in part on climate feedbacks. These natural processes can amplify/hasten the warming (a positive climate feedback) or counteract some warming (a negative climate feedback). How snow and ice respond to warming and the resultant impact on surface albedo is an important positive climate feedback. As the climate warms, snow and ice melt, the earth’s surface becomes less reflective (especially if sea ice melts, revealing open ocean, which is very dark), more solar energy is absorbed by the earth’s surface rather than being reflected back to space, causing the temperature to increase and the cycle to continue. from climateclassroom.org Prediction Predict which cup, white, black, or silver, will heat up faster. Which cup will reach the highest temperature the fastest, thus having lower albedo? Include a reason for your prediction. Think about different surface temperatures in the summer. Experiment In this investigation, identical metal cups have been painted black and white and one cup has been left its original silver color. Each cup will be fitted with a Styrofoam top to trap heat and a temperature probe will be inserted. The cups will be heated for 10 minutes using a heat lamp and the temperature will be measured each minute. The heat lamp will then be switched off and the temperature of the cups will be monitored each minute for an additional 10 minutes. Please record your data in the data table and/or Google sheets. Analysis 1. Which color cup reached a higher maximum temperature? Explain why you think this occurred? Think about reflection and absorption. 2. What did you notice about the rate of heat loss after the light was turned off? How did the heat gained over the first 10 minutes compare to the amount of heat reduction during the last 10 minutes? Did color appear to affect the rate of heat reduction? 3. Which cup would have a higher albedo? Why? 4. Which cup would have a lower albedo? Why? 5. Look at a globe or map of the world. Think about different types of surfaces on the Earth such as ice, oceans, forests, and large cities. a. What surfaces are best represented by the white cup? b. What surfaces are best represented by the black cup? c. Which surfaces absorb more solar radiation? d. Which surfaces reflect more solar radiation? 6. How does the color of the Earth’s surface affect air, land, and sea temperatures? Compose a well-written paragraph that addresses the investigative question: What effect does albedo have on surface temperature? Support your conclusion with evidence (data) from the albedo experiment.
