Week 13_climate-change (1)
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El Paso Community College *
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1301
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Geology
Date
Dec 6, 2023
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Uploaded by jessikadenn28
1 Name ________________________ GEOL1111 Principles of Earth Science Laboratory 13—Understanding Recent Climate Change (based on materials developed by Rondi Davies, Paul Ashwell, Erica Bigio, Jesse Kelsch, Mark Peebles and Xin Sun)
Activity 1 — Paleoclimate from Tree Rings (based on Carpenter et al., 2016)
Examine the figure below that shows tree growth rings. Notice the line that points to the growth ring that formed 550 years before the tree was cut. 1) Where are the youngest and oldest growth rings located? Youngest: Oldest: 2) How are the rings on the outer part of the tree different to the ones in the center? Outer rings: Inner rings: Mark the spot on the figure where the change in tree rings thickness occurs. Figure 1
. Cross-section of Douglas-fir archaeological beam from Broken Flute Cave, Arizona from Leavitt, S. & Bannister, B. (2009).
2 3) From the 550-year growth ring, count the number of rings to the center of the tree and record your findings. Then count the number of rings from 550 to the change in ring thickness and record this number. Assuming each ring represents one year of growth, how old is the tree? 550 to center = ________________, 550 to change = ________________, Age of tree = ________________ 4) Assume that the tree was cut down in the year 2000, what year did the tree rings begin to look different from the wider ones in the center? 5) Compare the date you calculated for when the tree ring pattern changed, to the graph in Figure 2. What was happening to the climate during that time? 6) From these observations, what would you suggest is the relationship between the tree ring thickness and climate? 7) From the graph in Figure 2, how much did temperature change over the 400 years between AD 1600 and 2000 relative to the decrease going into the Little Ice Age? Figure 2. Temperature data from the northern hemisphere for the last 1000 years relative to an average temperature (dashed line) (IPCC 1990 report)
0 0.5 -0.5
1 Activity 2 — Plotting Atmospheric Temperature and Carbon Dioxide data In this module you will be graphing recent average global temperatures and atmospheric carbon dioxide measurements from 1999 to 2019 (Table 1) versus time. Some background… Greenhouse Gases Gases that trap heat in the atmosphere are called greenhouse gases. These include: •
Carbon Dioxide (CO
2
): Carbon dioxide enters the atmosphere through burning fossil fuels (coal, natural gas and oil), solid waste, trees and wood products, and also as a result of certain chemical reactions (like the manufacture of cement). Carbon dioxide is removed from the atmosphere when it is absorbed by plants as part of the carbon cycle or by weathering of rock and soil. •
Water Vapor (H
2
O): This greenhouse gas likely accounts for 50% of Earth’s greenhouse effect. More water vapor is present in the air as the temperature of the air increases. •
Methane (CH
4
): Methane is emitted during the production and transport of coal, natural gas and oil. Methane is also emitted by livestock (e.g., cows) and other agricultural practices. It is emitted by the decay of organic waste in municipal solid waste landfills and by the thawing of permafrost in Arctic regions. •
Nitrous Oxide (N
2
O): Emitted during agricultural and industrial activities, as well as during combustion of fossil fuels and solid waste. The above information is from EPA (2012) “Greenhouse Gas Emissions” Table 1 Average global atmospheric temperature and carbon dioxide data. Year Temperature (˚C) CO2 (ppm) 1999 16.4 368.3 2000 16.4 369.5 2001 16.5 371.0 2002 16.6 373.1 2003 16.6 375.6 2004 16.5 377.4 2005 16.7 379.6 2006 16.6 381.8 2007 16.7 383.6 2008 16.6 385.5 2009 16.7 387.4 2010 16.7 389.9 2011 16.6 391.6 2012 16.7 393.9 2013 16.7 396.6 2014 16.8 398.6 2015 16.9 400.9 2016 17.0 404.3 2017 16.9 406.6 2018 16.9 408.6 2019 17.0 411.5
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2 Figure 3 Time versus Temperature and Carbon Dioxide Plot
3 Using your plot of time versus temperature and carbon dioxide, answer the following questions: 8) Between 1999 and 2019, how does the average global temperature change? (quantify your answer using degrees centigrade) 9) Between 1999 and 2019, how do atmospheric carbon dioxide values change? (quantify your answer using parts per million or ppm) 10) Based on your graph, what is the relationship between temperature and carbon dioxide? 11) What do you predict will happen to atmospheric water vapor if rising CO
2
leads to rising temperatures? How will changes to atmospheric water vapor further affect global temperatures? Be sure to explain your reasoning. 12) How might rising CO
2
levels lead to rising methane (CH
4
) levels?
1 Activity 3 – Interpreting paleotemperature and carbon dioxide data measured from the EPICA Ice Cores in Antarctica Your instructor will show a video about scientists in Antarctica extracting ice cores from the 800,000 year old continental glacier to learn about how the data in Figure 4 was collected. Link: https://www.youtube.com/watch?v=VjTsj-fi-p0 (also on Blackboard) Figure 4 Temperature change (light blue) and carbon dioxide change (dark blue) measured from the EPICA Dome C ice core in Antarctica (Jouzel et al. 2007; Lüthi et al. 2008). 13) How does the relationship between carbon dioxide and temperature in the ice core data (Figure 4) compare to your graph (Figure 3)? Explain. 14) What is the greatest temperature range (or the difference between the highest and lowest value) measured from the ice core data? How does this compare to the temperature variation during the Little Ice Age starting about 1400 years ago (Figure 2)? 15) What is the approximate time difference in years between two neighboring temperature peaks (representing a cycle of warming (interglacial) and cooling (glacial)).
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2 16) How does the duration of the Little Ice Age between 1400 and 1800 (Fig. 2) compare to the past ice age, or the time between the two most recent interglacial or warm periods from Figure 4. What does this inform you about natural cycles of warming and cooling? 17) What are the lowest carbon dioxide values measured during cooling or glacial periods? What are the highest carbon dioxide values measured during warming or interglacial periods? CO
2
during glacials: _______________, CO
2
during interglacials: _______________. 18) What is the atmospheric carbon dioxide value in 2019 (refer to Table 1)? Discuss the causes for the difference between this value and the 800,000 year record from the EPICA ice core. Activity 4 — Global changes versus local changes
So far in this lab we have looked at global average temperature trends. However, local temperature variations may appear very different to this global trend. A plot of the mean temperature trend from 1979 to 2020 in El Paso County is shown to left (based on the Historical-Climate-Tracker toolbox).
3 19) How does the value of the Best Fit trend line compare to the rate of temperature increase you plotted in Figure 3? (note, you will have to convert between ºF & ºC). 20) How has the mean temperature in the El Paso area changed when compared to the mean global temperature? Why do you think this is?