Understanding the Scientific Method in Physical Geography

Spring 2024 Name: ______________________________ Laboratory Investigation 1 The Scientific Method in Physical Geography 3. QUESTIONS 3.1. L1 Why is geography considered a science? (1 pt) 3.2. L1 What component of the scientific method is necessary if observation does not produce sufficient data? (1 pt) 3.3. L2 Using the scientific method, you have this research question:  Why does rice need irrigation during the summer in California? Rice grows mostly in the summer, and since California is a Mediterranean climate, summers are hot and dry. Your hypothesis is:  California receives insufficient rain to maintain rice during hot summers. Based on the information above, what types of data do you need to test the hypothesis? (1 pt) 3.4. L1 When does a hypothesis become a theory? (1 pt)

GEOG 1114 Lab Lab 1: The Scientific Method 4. PRACTICE AND APPLY YOUR KNOWLEDGE 4.1. Scientific evidence of the causes of recent ice melt in the Arctic Ocean. The North Pole is dominated by the Arctic Ocean, which is mostly capped by an ice pack formed by frozen seawater. Its average thickness varies between 3 and 4 meters (9.1 and 13.1 ft). Its surface size varies depending on the season, reaching its smallest extent in the late summer-early fall (September). However, every summer the ice pack becomes smaller and smaller as more ice melts. The shrinking of the ice pack has been happening throughout the 20 th century (Fig. 4.1.1), but has increased dramatically in the past four decades (map and upper graph in Fig. 4.1.2). Fig. 4.1 Sea ice cover maps for the annual minimum in September, for the periods 1850-1900, 1901-1950, 1951-2000, and 2001-2013. The maps show the sea ice extent in the lowest minimum during each period, which are in years: 1879, 1943, 1995, and 2012. Source: https://www.carbonbrief.org/guest-post-piecing-together-arctic-sea-ice-history-1850 2

GEOG 1114 Lab Lab 1: The Scientific Method Based on: Walsh, J. E., Fetterer, F., Stewart, J. S. and Chapman, W. L. (2016) A database for depicting Arctic sea ice variations back to 1850. Geographical Review, doi:10.1111/j.1931-0846.2016. 12195.x Fig. 4.1.2 Summer Arctic sea ice has declined dramatically since satellites began measuring it in 1979. The map shows the comparison of extent between 1980, 1998, and 200. The graph on top shows the changes in size from 1979 to 2015. The graph below shows the estimated volume of the ice for the periods 2003-2008, 2010-2011, and 2011-2112. Source: National Climate Assessment at https://nca2014.globalchange.gov/report/our-changing-climate/melting-ice/graphics/decline-arctic-sea- ice-extent The decline in extent means also a decline in the volume of ice, which the lower graph shows for three periods between 2003 and 2008 (lower graph in Fig. 4.1.2. As you can see the more time passes, the rate of melting and the loss of ice increases. This has serious consequences for the rest of the world, as that meltwater contributes to the rise of sea level. 3

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GEOG 1114 Lab Lab 1: The Scientific Method Now you may wonder the reason for the rapid melting of the Arctic ice pack. The hypothesis says: “The Arctic ice pack is melting because global temperatures increase due to the higher concentration of greenhouse gases in the atmosphere.” To test this hypothesis, observe the data in the graphs below. For the first part of the hypothesis (“the Arctic ice pack melts because global temperatures increase”), you can use the graph in Fig. 4.1.3. This graph shows the global temperature anomalies from 1900 - 2018 in relation to a “normal,” temperatures between 1981 and 2010. Fig. 4.1.3. Temperature anomalies for the period 1900-2018 in relation to the 1981-2010 average for Arctic and Global Temperatures. Note that the Arctic has been warming up faster than the rest of the world since 2000. Source: NOAA Research news at https://research.noaa.gov/article/ArtMID/587/ArticleID/2351/Study-In-2016%E2%80%99s-record-Arctic- warmth-a-glimpse-of-the-future 4

GEOG 1114 Lab Lab 1: The Scientific Method For the second part of the hypothesis (“global temperatures increase due to the higher concentration of greenhouse gases in the atmosphere”) use the graph in Figure 4.1.4. The graph shows the concentrations of CO 2 , the most abundant of the greenhouse gases, between 1900 and 2018. As we will see in Lab 8, greenhouse gases trap heat in the atmosphere resulting in higher temperatures, a process known as global warming. Fig. 4.1.4 Fossil fuel emissions estimated using records in metric tons of carbon. Source: Boden, T.A., Marland, G., and Andres, R.J. (2017). Global, Regional, and National Fossil-Fuel CO2Emissions . Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. Department of Energy, Oak Ridge, Tenn., U.S.A. doi 10.3334/CDIAC/00001_V2017. Finally, it is important to mention that scientists use data to model ice melting in the future. Such a model would be a predictive model, and would involve computing simulation models of ice melting in the future decades. That model would serve to assess the possible global consequences of rapid ice melting that will cause levels to rise and flood of shallow islands and low lands around the world. 5

GEOG 1114 Lab Lab 1: The Scientific Method Questions: 1. L1 If the data in Figures 4.1.3 and 4.1.4 explain the melting of Arctic ice, consider the statement:  The Arctic ice pack melted as a result of increased global temperatures due to a higher concentration of greenhouse gases in the atmosphere. Is this statement a hypothesis, theory, or law? (1 pt) Explain your answer. (1 pt) 2. L3 If ice in the Arctic is melting at the rate shown in the graphs of Figure 4.1.2, what can you expect generally for the ice cap during the 2020-2030 period? (1 pt) 3. L2 Using the boxes and arrows below, construct a causality sequence that explains the flooding of lowlands originating from global warming. Write directly on the boxes or on the designated spaces for 1, 2, and 3 below. Clue: Remember A causes B, B causes C. (1 pt) 6

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GEOG 1114 Lab Lab 1: The Scientific Method 1. ________________________________________________________________ 2._________________________________________________________________ 3.__________________________________________________________________ 4. Seawater floods lowlands 4.2. The extinction of mammoths and other megafauna in North America. Hypotheses and data. Megafauna is a term that refers to any animal that weighs more than 44 kg (97 lb). That is, they are large animals, some of which may include horses, bison, lions, and elephants. During the Pleistocene (also known as the ice age), a number of mammal fauna of considerable size roamed the subcontinent of North America. Examples of such megafauna include woolly mammoth ( Mammuthus primigenius ), the Columbia mammoth ( Mammuthus columbi ), the short-faced bear ( Arctodus simus ), the saber- toothed cat ( Smilodon fatalis ), the giant beaver ( Castoroides ohioensis ) the Shasta ground sloth ( Nothrotheriops shastensis ), and a number of other not-so-larger animals, such as camel ( Camelops spp.), dire wolf ( Canis dirus ), and wild horse ( Equus spp.) (Figure 4.2.1) 7

GEOG 1114 Lab Lab 1: The Scientific Method Figure 4.2.1 Select North American extinct mammals Source: Wikimedia Commons. All these animals were part of 90 genera of mammals that disappeared during the American megafaunal extinction event around 12,700 years ago. The causes of their disappearance are not known. However, along with extensive scientific research, several theories have been proposed to explain the causes of this massive extinction of megafauna. The hypotheses that explained the causes of the megafauna extinctions are: 1. Climate change hypothesis. Animals could not adapt to the rapid climatic changes occurring around the time of the extinctions. 2. Overkill hypothesis. Humans killed the animals through exhaustive hunting. 3. Disease hypothesis. Diseases brought in to the continent from Asia by humans and other animals infected the North American fauna. 4. Meteorite impact hypothesis. A meteorite hit North America causing massive fires and sudden climatic change. 8

GEOG 1114 Lab Lab 1: The Scientific Method Of the four hypotheses, number 3 and 4 lack strong scientific evidence. For example, no sign of the impact of the meteorite has been found and no direct evidence of fires appear clear for that time. Likewise, the dead animals found do not present evidence of dying of sickness. However, hypotheses 1 and 2 have stronger evidence in the form of extensive sets of data. A group of two scientists by the names Jack Broughton and Eric Weitzel compiled data to test the climate change and the overkill hypotheses. They published their result in Nature Communications , a very prestigious scientific journal. They obtained data from different parts of the United States (See the map on Figure 4.2.2). Figure 4.2.2 Map of the contiguous United States and southern Canada. Indicated are the frequency of dates by state or province for the directly dated megafauna sample and the distribution of archeological radiocarbon dates. Source: Broughton, J.M. and Weitzel, E.M., 2018. Population reconstructions for humans and megafauna suggest mixed causes for North American Pleistocene extinctions. Nature communications , 9 (1), pp.1-12. Source: Nature Communications https://www.nature.com/articles/s41467-018-07897-1 9

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GEOG 1114 Lab Lab 1: The Scientific Method Broughton and Weitzel, compiled five datasets to test hypotheses 3 and 4: 1. Radiocarbon ages of the bones of dead animals, which permit placing their deaths in time. These data are used as proxy to reconstruct the populations of each animal species during the period before, during, and after the extinction. 2. Radiocarbon ages from hunter’s sites. These data are used as proxy to reconstruct the populations of hunters at a certain time during the period before, during, and after the extinction. 3. Temperature data obtained from oxygen isotopes in the water that forms the ice of ice caps (Greenland and Antarctica). 4. Carbon dioxide (CO 2 ) concentrations obtained from air trapped in bubbles in the ice caps. 5. The difference in energy from the sun between summer and winter in North America before, during, and after. The researchers plotted their datasets in the graphs below. However, before you proceed with the graphs and the questions, familiarize yourself with the graph below, which shows the change in population of mammoths in the present territory of the United States through time. Fig. 4.2.3 Key. The x axis (horizontal axis). Notice that you have to multiply the number by 1000, so 10 means 10,000 years in the past. The y axis (vertical axis) is size of populations. The time of the Clovis hunters is marked with the narrow red vertical strip. The time of the climatic event known as Younger Dryas is marked by the light blue strip. The purple shadow and the line behind the graph is the projection of mammoth population if they had not gone extinct. Source: Broughton, J.M. and Weitzel, E.M., 2018. Cited above. 10

GEOG 1114 Lab Lab 1: The Scientific Method The y-axis (the vertical axis) is the relative amount of radiocarbon ages. Thus, the grey curve tells you the relative population numbers of each animal. The x-axis (horizontal) is the time span between 20,000 and 10,000 years ago. Notice : the axis begins with the present and moves to the past as you go to the right. The time of the Clovis hunters is marked with the vertical red strip, roughly around 13,000 years. The time of the Younger Dryas is a time when climate changed considerably and is marked by the cyan strip, roughly indicating a time between 12,900 and 11,700 years ago. The line and purple shadow behind the animal population graphs shows a projection of the population of each animal into the future if they had not gone extinct. In other words, the line is a predictive model . Now, look at the graphs showing the population data for mammoths and all other megafauna and the populations of human hunters (Fig. 4.2.4). Analyze the graphs, make notes if necessary, and proceed to answer the practical questions below. 11

GEOG 1114 Lab Lab 1: The Scientific Method Figure 4.2.4 Population graphs for a) mammoths, b) mastodons, c) Shasta ground sloths, d) horse, e) saber-toothed cat, and f) human hunters. Graphs for g) temperature changes, h) carbon dioxide (CO2), and i) seasonal differences in insolation between summer and winter. Source: Broughton, J.M. and Weitzel, E.M., 2018. Cited above. 12

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GEOG 1114 Lab Lab 1: The Scientific Method Questions 4.2.1. L3 Analyze the lower part of the graph in Figure 4.2.4. What climatic changes do you see occurring during the Younger Dryas? (2 pts) 4.2.2. L1 Based on your interpretation of the above data choose the most likely cause of the extinctions. (1 pt) A) Overkill B) Climate Change C) Both Climate Change and Overkill. D) Neither overkill nor climate change. Provide reasoning for your choice. (2 pt) 4.2.3. L2 Look at the graphs Figure 4.2.4. What similarities do you find between the populations of the now-extinct species? (1 pt) 13

GEOG 1114 Lab Lab 1: The Scientific Method 4.2.4. Compare and contrast the curves of the saber-toothed cat and the human hunters beginning with the appearance of the Clovis hunters (red strip) and ending with the present (left-hand side of graph). (1pt) 4.2.5. L1 Why is the Disease Hypothesis a hypothesis and not a theory? (1 pt) 6. L1 What would you propose to do to test the meteorite hypothesis? Using the steps in the scientific method, explain your proposed experiment. (2 pt) 14

GEOG 1114 Lab Lab 1: The Scientific Method Points Section 1: Section 2: Total: ____________ out of 18 points 15

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Lab 1-3

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