Unit 12 Lab Climate Change Fall 23
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1 UNIT 12: CLIMATE CHANGE Bradley Deline, edited by Randa Harris I
NTRODUCTION
Climate is an average of the long-term weather patterns across a geographic area, which is a complicated metric controlled by factors within the lithosphere, atmosphere, cryosphere, hydrosphere, biosphere, and anthrosphere as well as factors beyond our own planet. It is helpful to separate out humans from other life (anthrosphere verses biosphere) for several reasons, primarily because many of our activities are unique amongst life (industrialization) and it is helpful in understanding our role in climate change. Therefore, the science examining past, current, and future climate is extremely complex and interdisciplinary. You may not think of climate as a geological field of study, but the history of climate is recorded within rocks, the current climate is altered by geologic events, and future climate will be influenced by our use of geological resources such as fossil fuels. In addition to the complex nature of this subject, it is also one, if not the most, important scientific fields of study both in terms of understanding the dynamics and implications of future climate change as well as attempting to combat or mitigate the potential effects. Though the basic science behind climate and climate change has been well studied to a point of near consensus within the scientific community, there is still significant debate amongst the broader population. This is likely related to many factors beyond science including economics, politics, the portrayal of the science by the media, and the overall public’s scientific literacy. Gaining a better understanding of this issue is difficult given the enormous wealth of information and disparity of literacy available. This lab will explore climate change indicators and examples and how it relates to our understanding of the world around us. Learning Outcomes: After completing this chapter, you should be able to:
•
Describe the climate system and how different variables are related •
Discuss how ancient climate patterns are reconstructed •
Understand feedback mechanisms, both positive and negative •
Understand climate proxies and how they are used to reconstruct climate •
Describe the information needed to make conclusions regarding scientific patterns and how climate models should be constructed Key Terms: Albedo Climate Proxies Climate System Greenhouse Gases Ice Extent Negative Feedback Positive Feedback
2 T
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As was previously mentioned, climate is the long-term weather pattern across a region. It is important to emphasize the long-term portion of the definition to establish that climate is different from weather. Weather is the local and short-term patterns in temperature, humidity, precipitation, atmospheric pressure, wind, and other meteorological variables. As you well know, weather fluctuates throughout the day, week, month, and year such that it is difficult to see any trends beyond the random noise in the system. If you take a long-term view of weather we can begin to see patterns across time and geography that help to better understand and identify the factors that influence the climate system. The climate system is the interconnected network of variables that influence the earth’s climate, which includes components from the lithosphere, atmosphere, hydrosphere, cryosphere, biosphere, anthrosphere, and solar system. The heat that feeds this system comes from two primary sources. First, there is heat radiating from the Earth itself, which is coming from the decay of radioactive material and residual heat from the formation of the earth. This heat is not distributed equally, with more heat escaping in areas where the crust is thinner, such as divergent boundaries. More significantly, the earth receives heat from solar radiation. Again, this heat is not distributed equally across the earth’s surface and the amount of energy received is related to the angle at which the solar radiation hits the surface of the earth (Figure 1). If the solar radiation hits perpendicular to the surface more heat is absorbed than if it hits at an oblique angle, which is why the tropics are warmer than the poles. Figure 1.
The Earth’s shape influences the angle at which the sun’s rays hit the surface, from perpendicular at the equator to parallel at the poles. This creates large climate differences across the Earth. The material on the Earth’s surface is also important in that materials react differently to solar radiation. Some materials, normally dark in color, absorb and reradiate heat, most of which is retained at the surface of the planet. You are likely familiar with this if you have ever walked barefoot on dark concrete or asphalt in the summer. Other materials that are shiny or light in color reflect the solar radiation off the Earth’s surface. Materials such as snow or ice are particularly effective at reflecting solar radiation. This is the reason Arctic explorers must use
3 eye protection to avoid snow blindness. The proportion of solar radiation that is reflected off the Earth’s surface is called albedo
, which can vary depending on the type of ground cover. For instance, the Earth’s albedo is higher when it is covered with large expanses of glacial ice and thus the amount of sunlight absorbed and the temperature measured are lower. Once heat is reradiated off of the Earth’s surface it travels up into the atmosphere. Certain gases in Earth’s atmosphere, called greenhouse gases
, allow sunlight to pass but absorb terrestrial energy and radiate it in all directions including back to the surface of the Earth. These gases, such as water vapor, carbon dioxide, and methane represent a tiny, though important fraction of the material in the atmosphere. Different greenhouse gases vary both in how effectively they absorb and reradiate energy and their relative proportions in the atmosphere, such that a higher concentration of potent greenhouse gases can retain more thermal energy within the atmosphere. The rest of the reflected and radiated energy escapes from the atmosphere and dissipates into space. Several factors can influence the simplified version of the climate system described above. The amount of radiation produced from the sun varies over time. In addition, the shape of our orbit around the sun varies over time from more circular to more elliptical because of the gravitational influences from other planets in our solar system. The angle at which solar radiation hits the planets’ surface is influenced by the tilt and wobble of the Earth’s axis. The distribution of water, ice, snow, vegetation, and other materials on the Earth’s surface control the Earth’s albedo and can change over time. The proportion of greenhouse gases can change dramatically depending on the rate of plate motion as well as the amount of volcanism, photosynthesis, weathering of rocks, burning of fossil fuels, and many other factors (to examine trends on climate and carbon dioxide levels see Figure 5 later in the lab). The efficiency of the transportation of heat across the surface of the Earth also influences climate. Heat is transferred across the surface of the planet by wind, ocean currents, and storms. Therefore, the position of the continents as well as air and ocean currents affect climate and can change over time. The components in our atmosphere are also important, including water vapor and aerosols (dust). Water vapor in the atmosphere is a greenhouse gas, can reflect incoming solar radiation, and is the source of precipitation. Aerosols can come from the Earth’s surface, ash from volcanoes, and the burning of fossil fuels and can alter climate by reflecting incoming solar radiation before it reaches the Earth’s surface. There are numerous additional factors that also have some level of effect on the climate system. At this point you should be able to recognize the complexity of the climate system based on the number of variables and how those variables can change over time. It is also important to recognize that all of these variables are connected. For instance, if a volcano erupts it adds some thermal energy to the climate system; it produces aerosols that block solar radiation from hitting the Earth’s surface, and produces greenhouse gases that retain heat. Notice that these factors do not all influence climate in a consistent way. The change of one variable as the result of another is called feedback, which can be either positive or negative (Figure 2). Positive feedback
reinforces the initial change no matter the direct of that change. For instance, if the Earth warms, ice melts and reduces the albedo, which causes even more warming. This can also occur in the opposite direction, if the Earth cools, ice forms and increases the albedo, which causes more cooling. Negative feedback
counteracts the initial change no matter the direction of the initial change. For instance, if the Earth warms, more area becomes arid, resulting in an increase in the amount of dust in the atmosphere, which reflects solar radiation causing cooling. Again, the
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4 opposite works, if the Earth cools, less area is arid resulting in a decrease in the amount of dust in the atmosphere, which causes warming. Therefore, an understanding of the climate system requires an identification of all of the important climate variables, how they are related to each other, the speed at which they can change, and the magnitude and direction of change of each feedback loop. The ideal way to gain a better understanding of the climate system is to study it through geologic history. Figure 2.
A simple diagram showing the relationship between two variables with either positive or negative feedback following a positive (A) or negative (B) initial change. C
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The first method most students think about when we talk about recording climate is using a thermometer to directly measure temperature. There are actually a few problems reconstructing climate patterns this way, including that a thermometer gives a very local signal and more importantly, thermometers are a relatively recent invention. Given that direct observations do not give us the long-term trends needed to establish climate change or patterns, we must look at a natural recorder of climate called a climate proxy
. As climate changes it affects the deposition of sedimentary rock, rock chemistry, and fossil organisms that scientists can detect in order to reconstruct ancient climate patterns, in a field called paleoclimatology. An individual climate proxy may not give a clear signal of global climate for a couple of reasons. First, proxies show a history of the area in which they were formed, not of an entire region. Second, an individual proxy, which may have a long or a short record, can record the short-term
5 variability of weather events. And third, most climate proxies are influenced by multiple factors. For instance, the thickness of tree rings (dendrochronology) is a wonderful proxy for temperature. Trees grow more in warmer years (producing thicker rings) and less in colder years (producing thinner rings). However, a tree could also grow slowly because of a drought or because of an infestation of pests even if it was a warm year. If all of the individual proxies show local patterns, with some degree of weather related noise, and possibly influenced by other factors, how do we then reconstruct long-term global temperature records? The answer lies in increasing the size of the dataset. If temperature is the most important variable influencing the proxies, and we combine hundreds to thousands of individual proxy records, an overarching pattern emerges from the noise. Again, an individual proxy record may be contrary to the overall trend, but that is expected since a local region can have a cold winter in the midst of an overall hot year for the planet. To illustrate this consider the following: say we want to reconstruct overall economic patterns over the past few hundred years in the United States of America. We could examine lots of proxies for economic growth, such as employment, the stock market, individual wealth, or rates of home ownership to name a few. If we only looked at one of these proxies we likely would not get a clear picture of change. Also, if we only looked at Macon, Georgia, for example, we would be unlikely to see a trend that mimics the entire country. For instance, if a new factory opened outside of Macon, GA that would be a huge economic benefit for the city, but not for the country overall. Again, the more data we have, whether it is for economics, or climate, or any other complex system, the clearer the signal becomes over the local and random noise. One of the most commonly used climate proxy is the measurement of oxygen isotopes. Isotopes are atoms of the same element that differ in their weights because of differences in the number of neutrons in the nucleus of the atom. Multiple isotopes of oxygen are stable, meaning they do not radioactively decay over time. Oxygen has two stable isotopes that occur in a constant ratio on Earth. However, certain minerals (like calcite or ice) prefer one of the isotopes over the other within their crystal structure (a slightly larger or smaller atom fits better). This preference results in a ratio of oxygen isotopes that is different from the ratio found in other materials; this difference is called fractionation. The amount of fractionation in oxygen isotopes is temperature dependent, such that the mineral calcite has a different ratio of oxygen isotopes if it was formed in near freezing versus warm water temperatures. Using oxygen isotopes we can get climate records from many different sources, including coral, clams and other mollusks, the skeletons of single-celled organisms, and ice cores to name a few. Ice cores (as shown in Figure 3) can contain a wealth of climate data in addition to temperature data from oxygen isotopes, such as air bubbles that record the levels of greenhouse gases, concentrations of windblown aerosols, and ash from volcanic eruptions.
6 Figure 3. A short segment of an ice core that records ancient climate patterns. Image courtesy of Ludovic Brucker, NASA Other proxies include the extent of glacial sediment, sea level curves, pollen (palynology), and fossils. For instance, climatologists have used several features within fossil plants to reconstruct climate, largely because these organisms are sensitive to climate. These proxies include the thickness of tree rings, the shape of the leaves (toothier leaves are more common in colder climates), and the density of pores on leaf surfaces (more pores are needed with lower concentrations of carbon dioxide, which is necessary for photosynthesis). As was mentioned before, by combining hundreds to thousands of individual climate records we can start to gain insight into overall climate trends. For instance, the Intergovernmental Panel on Climate Change (IPCC) and the National Oceanic and Atmospheric Administration (NOAA) regularly compile multiple types of proxy records from across the world (Figure 4) to reconstruct climate patterns (Figure 5). The accuracy of the climate records very much depends on the time frame being considered, with more certainty in the patterns of the recent past (Cenozoic) and less the further back in geologic time we are examining. There is debate surrounding the interpretation of individual proxies and the resulting climate records, which largely stems from the economic and political aspects of climate change. At any point when investigating climate change, it is wise to learn more about the data involved – how much data was used, over what time period, from how many locations across the Earth, over what months of the year, using what proxy or proxies. Erroneous conclusions can be drawn from limited data sets.
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7 Figure 4. Distribution of individual climate proxies used in the construction of Figure 5. Image from the National Ocean and Atmospheric Administration. Figure 5. Climate reconstruction over the last 1300 years using multiple climate proxies (different colored lines) from “Climate change 2007: the physical science basis”; Contribution of
8 Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change Jansen, E. J. Overpeck, K. R. Briffa, J. C. Duplessy, F. Joss, V. Masson-Delmotte, D. Olago, B. Otto-Bliesner, W. R. Peltier, S. Rahmstorf, R. Ramesh, D. Raynaud, D. Rind, O. Solomina, R. Villalba, and D. Zhang. Courtesy of NOAA. L
AB E
XERCISE Part A – Sea Level Rise The National Oceanic and Atmospheric Administration (NOAA) has created a Sea Level Rise Viewer, accessed here
. This web mapping tool can help you visualize the impacts of sea level rise at different amounts, and can be very useful for city planners along the coast. It bases it measurements on mean higher high water (MHHW), the average height of the highest tide recorded at a tide station each day. You can move the MHHW using a scale bar long the left side of the page and observe the changes at different heights. You can see the actual water rise simulation when you find a location with this symbol: You can also use the Local Scenarios tab on the left (and with this symbol on the map - to investigate different sea level rise scenarios in a particular area. The tab called Vulnerability adds social and economic data to the map, so communities can determine the impacts of sea level rise on those most vulnerable (the most vulnerable areas are marked in dark red, decreasing in vulnerability as the red lightens). 1. Using the Sea Level Rise Viewer, type in Sunset Beach, CA in the search box at the top. This beach is located outside of Los Angeles. Use the MHHW bar to raise the MHHW bar, 1 foot at a time and observe what happens to Sunset Beach and the wildlife and ecological reserves to the north and south of Sunset Beach. Lower the water level back to 0. Click on the water drop symbol at Sunset Beach, and raise the water level using the slider. At what point is the road in the left of the picture submerged? a. 1 foot b. 2 feet c. 3 feet d. 5 feet 2. Now select the Local Scenarios tab on the left, or choose the icon shown above in the text. Select the location of Los Angeles, CA, just to the west of Sunset Beach. Select View by Scenario along the top, and choose the Intermediate scenario. By 2060, how much will the water level have risen here? a. 0.89 feet b. 1.57 feet c. 2.66 feet d. 2.82 feet
9 3. Now select the Vulnerability tab on the left. Make sure the MHHW scale is at 0. Zoom in to the Long Beach area and examine its vulnerability. Which of the following areas is most vulnerable to sea level rise? a. Waggaman b. San Pedro c. Lomita d. Rolling Hills Part B – Climate Change and the National Parks Climate change is having an impact in all the national parks, though the parks may be vulnerable for different reasons. We will explore several parks to understand more about the issues they face. We are going to start with Everglades National Park in Florida. Do some research on the park at the nps.gov website (go to Learn About the Park, Nature, Climate Change – also check each tab at Climate Change), then answer the questions below. 4. Go to 25 13 50.02N 80 36 36.97W and zoom to an eye altitude of ~10 miles. These are saline glades, an area of sparsely vegetated marsh that has little freshwater. Only a few plant species can survive in these conditions, including the red mangrove. In the past 50 years, the red mangrove has moved further inland, displacing other species. What factors have made it easier for the red mangrove to move inland? a. sea level rise, canals, and roads have increased the exchange of saline and fresh water in the marsh b. localized flooding has brought more freshwater into the area c. none of the choices are correct 5. Which of the following steps has Everglades National Park made to combat climate change? a. use of solar powered water heaters b. increased the use of hybrid vehicles c. trams are fueled with biodiesel d. all of the answer choices are correct Kenai Fjords National Park and Preserve in Alaska is home to approximately one quarter of all of Alaska’s glaciers – over half of the park is covered by ice. Do some research on the park at
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10 the nps.gov website (go to Learn About the Park, Nature, Environmental Factors, Climate Change. Make sure to click on the Learn more about the science link at the bottom of this page, and check out the articles at the bottom of this page), then answer the questions below. 6. How much has Bear Glacier retreated since its maximum in 1888? a. 2.1 miles b. 2.7 miles c. 3.2 miles d. 4.0 miles 7. Due to increased temperatures in the ocean off Alaska, harmful algal toxins have been able to thrive. During the last 20 years, what has been the increase in marine mammal deaths related to these harmful algal toxins? a. 14% b. 24% c. 37% d. 39% e. 40% Yosemite National Park in California is a varied landscape, with meadows, wilderness, giant trees, waterfalls, and large peaks. Climate change could have a great impact on this location. Do some research on the park at the nps.gov website (go to Learn About the Park, Nature, Environmental Factors, Climate Change), then answer the questions below. 8. Between 1950-2010, what was the rate of temperature rise within Yosemite? a. 1.6
o
F per century b. 3.4
o
F per century c. 4.3
o
F per century d. 6.1
o
F per century 9. Go to 37 44 29.65N 119 16 7.43W and zoom to an eye altitude of ~25,000 feet. This is Lyell Glacier, a body of ice within Yosemite that is technically no longer a glacier due to the fact that it hasn’t moved in recent years. Between 1883-2017, how much did the surface area of this glacier decrease by? a. 42-50% b. 51-60% c. 67-78% d. 70-81%
11 10. While a precise prediction is difficult, how long do scientists estimate that it will be before there are no longer any glaciers within Yosemite? a. within ~5 years b. within decades c. within a century d. within ~1,000 years
12 STUDENT RESPONSES 1. Using the Sea Level Rise Viewer, type in Sunset Beach, CA in the search box at the top. This beach is located outside of Los Angeles. Use the MHHW bar to raise the MHHW bar, 1 foot at a time and observe what happens to Sunset Beach and the wildlife and ecological reserves to the north and south of Sunset Beach. Lower the water level back to 0. Click on the water drop symbol at Sunset Beach, and raise the water level using the slider. At what point is the road in the left of the picture submerged? a. 1 foot b. 2 feet c. 3 feet d. 5 feet 2. Now select the Local Scenarios tab on the left, or choose the icon shown above in the text. Select the location of Los Angeles, CA, just to the west of Sunset Beach. Select View by Scenario along the top, and choose the Intermediate scenario. By 2060, how much will the water level have risen here? a. 0.89 feet b. 1.57 feet c. 2.66 feet d. 2.82 feet 3. Now select the Vulnerability tab on the left. Make sure the MHHW scale is at 0. Zoom in to the Long Beach area and examine its vulnerability. Which of the following areas is most vulnerable to sea level rise? a. Waggaman b. San Pedro c. Lomita d. Rolling Hills 4. Go to 25 13 50.02N 80 36 36.97W and zoom to an eye altitude of ~10 miles. These are saline glades, an area of sparsely vegetated marsh that has little freshwater. Only a few plant species can survive in these conditions, including the red mangrove. In the past 50 years, the red mangrove has moved further inland, displacing other species. What factors have made it easier for the red mangrove to move inland? a. sea level rise, canals, and roads have increased the exchange of saline and fresh water in the marsh b. localized flooding has brought more freshwater into the area c. none of the choices are correct 5. Which of the following steps has Everglades National Park made to combat climate change? a. use of solar powered water heaters b. increased the use of hybrid vehicles c. trams are fueled with biodiesel d. all of the answer choices are correct
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13 6. How much has Bear Glacier retreated since its maximum in 1888? a. 2.1 miles b. 2.7 miles c. 3.2 miles d. 4.0 miles 7. Due to increased temperatures in the ocean off Alaska, harmful algal toxins have been able to thrive. During the last 20 years, what has been the increase in marine mammal deaths related to these harmful algal toxins? a. 14% b. 24% c. 37% d. 39% e. 40% 8. Between 1950-2010, what was the rate of temperature rise within Yosemite? a. 1.6
o
F per century b. 3.4
o
F per century c. 4.3
o
F per century d. 6.1
o
F per century 9. Go to 37 44 29.65N 119 16 7.43W and zoom to an eye altitude of ~25,000 feet. This is Lyell Glacier, a body of ice within Yosemite that is technically no longer a glacier due to the fact that it hasn’t moved in recent years. Between 1883-2017, how much did the surface area of this glacier decrease by? a. 42-50% b. 51-60% c. 67-78% d. 70-81% 10. While a precise prediction is difficult, how long do scientists estimate that it will be before there are no longer any glaciers within Yosemite? a. within ~5 years b. within decades c. within a century d. within ~1,000 years