Brodie Baile Global Climate Change Lab
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Colorado State University, Fort Collins *
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Course
121
Subject
Geology
Date
Apr 3, 2024
Type
Pages
10
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GEOL 121 Name_________________________________ Lab Section ____________ This module was initially developed by O’Reilly, C.M., D.C. Richardson, and R.D. Gougis. 15 March 2017. Project EDDIE: Climate Change. Project EDDIE Module 8, Version 1. http://cemast.illinoisstate.edu/data-for-students/modules/climate-
change.shtml
. Module development was supported by NSF DEB 1245707. GLOBAL CLIMATE CHANGE LAB Student Handout Learning objectives: •
To analyze global temperature data to see if Earth’s average global temperatures are really increasing •
To analyze CO
2
data to see if atmospheric levels are really increasing •
To correlate CO
2
data with global temperature to see if there is a relationship •
To compare current trends with rates of change during pre-historic periods using ice core data •
To interpret what these results mean for understanding current climate change Why this matters: Current climate change is affecting many aspects of the environment, with socio-
economic consequences. For example, a warmer climate can allow new diseases to be introduced and persist (e.g. West Nile became established in the United States after an unusually warm winter allowed the mosquitos that carry the virus to survive and spread). We are concerned not only with the actual temperature, but also with the rate that the temperature changes. Very rapid changes make it more difficult for humans to adapt and more likely that other species cannot adapt and will go extinct. Activity A: How much are temperature and atmospheric CO
2
changing? Changes in air temperature -
Scientists from the Goddard Institute for Space Studies, NASA, compiled temperature datasets from weather stations all over the world to create the dataset you are going to be working with today to answer the question: Is earth “warming”? The data you will use are from years 1880-2022. 1.
Before you conduct your analysis, you should first make your predictions. What slope would indicate a warming Earth? What slope would indicate Earth’s average global temperature was not changing? What slope would indicate a cooling Earth? Sketch lines in the axes below to show what the expected slopes would be in these different scenarios. cooling warming no change o
C
o
C
o
C
time time time
GEOL 121 Global Climate Change Lab 2 Getting the air temperature data: These data are compiled by the Goddard Institute for Space Studies, NASA, and are made available at https://data.giss.nasa.gov/gistemp/
. For this lab, the data has been organized into an Excel spreadsheet for you, which you can find on the lab Canvas page. Open up the Global Temperature dataset by selecting the correct tab at the bottom of the spreadsheet.
2.
Examine Graph A.
Describe in words how global temperature has changed between 1880 and 2022. exponentially increasing 3.
We will now determine the rate of temperature change. Determining rates of change graphically is straightforward. The average rate of change is just the change in temperature divided by the change in time, or change in y divided by the change in x, or the slope of a line that fits through the data. Excel can calculate the slope of a line very easily. In Graph B
, a linear trendline has been added to the global temperature data (
black dashed line
). The equation for the trendline is also shown (outlined in black). The equation is written in the form y = mx + b
, where m
is the slope and b
is the intercept. Another name for the slope (
m
) is the rate of change. The R-squared (R
2
) is a statistic resulting from a linear regression analysis, which is the statistical name for what we just did by adding a trendline. It describes the proportion of variation in the dependent variable explained by the independent variable. When R
2
~1, the data form a perfectly straight line. As the data become more scattered from the line, R
2
decreases toward 0. Higher R-squared values indicate a stronger relationship between the two variables. Record the R
2
value down with your slope. a.
Equation for the line: y=.0077x-15.053 b.
R
2
= .763 c.
Rate of air temperature change (include units): .0077 c/year d.
Given your analysis, is Earth warming? How do you know? It is warming because of the positive rate of air temperature change.
GEOL 121 Global Climate Change Lab 3 4. Many scientists suggest that drastic changes in global temperature began in the mid-1900s when fossil-fuel-powered transportation became a mainstay for most families. We can test this hypothesis by adjusting the trendline so that it only looks at the most recent decades, after personal transportation became common. The red solid line
on Graph B
only includes data from 1965-2022. Record the values for the red solid trendline below. a.
Equation for the line: .0183x-36.109 b.
R
2
= .9194 c.
Rate of air temperature change (include units): .0183 c/year d.
Compare the slopes of these two lines (1880 through 2022 (black) versus 1965 through 2022 (red)). Does your analyses support the hypothesis that the rate of global average temperature is greater in recent decades? It supports the hypothesis because the slope as the years pass gets steeper. Changes in atmospheric CO
2
- In 1958, Dr. Charles David Keeling (1928-2005), who was a scientist at Scripps Institute of Oceanography, began collecting data on atmospheric CO
2
concentration at the Mauna Loa Observatory located in Hawaii. This dataset is what allowed us to understand the degree to which climate change is human-caused through our burning of fossil fuels and release of CO
2
into the atmosphere. Due to his scientific achievements, Dr. Keeling was awarded the National Medal of Science by President George W. Bush in 2002. This is the highest award for lifetime scientific achievement that can be granted in the U.S. Today, you get to analyze this same dataset, except that you have more data than was available to Dr. Keeling and his colleagues, because your dataset extends up to current time. Getting the atmospheric CO
2
data: The longest measurements of atmospheric CO
2
concentrations have been done in Mauna Loa, Hawaii. The simplest way to access the data is directly from the Mauna Loa page. http://www.esrl.noaa.gov/gmd/ccgg/trends/ For this lab, the data has been organized into an Excel spreadsheet for you, which you can find on the lab Canvas page. Open up the dataset by selecting the Mauna Loa CO
2
tab at the bottom of the spreadsheet.
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GEOL 121 Global Climate Change Lab 4 1.
Examine Graph C. Describe in words how atmospheric CO
2 has changed between 1959 and 2022. It increased 2.
The black dashed line on Graph C
is a linear trendline applied to the CO
2
data. Record the equation and R
2
for this trendline below. Determine the current rate of change for atmospheric CO
2
data, as you did for air temperatures. a.
Equation for the line: 1.6244x-2875.2 b.
R
2
= .9818 c.
Rate of air CO
2
change (include units): 1.6244 ppm/year d.
Based on your analysis, has atmospheric CO
2
concentration increased? How confident are you in these results? Yes, the slope is positive, CO2 levels increased. I'm confident.
GEOL 121 Global Climate Change Lab 5 Activity B:
How related are the changes in temperature and CO
2
? 1.
To determine whether a change in CO
2
corresponds well with a change in air temperature, you can plot temperature against CO
2
.This is done for you in Graph D
. Describe in words the relationship between atmospheric CO
2
and global temperature. global temperature increases as atmospheric CO2 increases. 2.
The blue solid line is a linear trend line through the CO
2
and temperature data. Record the equation and R
2
below. a.
Equation for the line: .0104x-3.726 b.
R
2
= .9259 c.
Based on your analysis, could atmospheric CO
2
concentration explain the increase in average global temperature? How strong is the relationship between CO
2
and temperature? How can you tell? CO2 is a greenhouse gas that traps heat in the atmosphere. If CO2 increases, more heat will be trapped in the atmosphere which will lead to an increase in global temperature. This is a strong relationship between them.
GEOL 121 Global Climate Change Lab 6 Activity C: How do current trends compare to pre-historic rates of change? An exploration of the Vostok Ice Core - When analyzing Earth’s climate, it is important to remember that Earth is 4.54 billion years old. Our analyses so far have only looked at recent history. How can we compare the recent data to pre-historic time? Are the current rates of change similar or different than those the earth has experienced in the past? To explore this, we can use data taken from ice cores that were drilled at the poles. Hundreds of ice cores have been extracted from polar ice because they contain valuable data on atmospheric chemistry over pre-historic time. These valuable data exist in tiny air bubbles that are trapped in the ice. These air bubbles contain the same gases in the same ratios as the atmosphere at the time when the ice formed. The data you will be analyzing today are from ice cores extracted from the Vostok research station in Antarctica. As you have probably assumed, the depth of the ice core is related to how old the ice is; deep ice is older. There are two other variables that you will be analyzing from the ice cores. The first is temperature, which is reflected by isotopic ratios in the ice of the core so that these isotopic ratios can be converted into air temperatures. The second variable you will analyze is CO
2
concentration, which has been measured from air bubbles trapped in the ice. We can use these data to see what rates of change were like during this pre-historic period, during which human activity has been minimal. The Vostok ice core data is available through the Carbon Dioxide Information Analysis Center (CDIAC) http://cdiac.esd.ornl.gov/
. For this lab, the data has been organized into the Excel spreadsheet for you in the Vostok CO
2
and Vostok Temp tabs. In these data, temperature is calculated from the ‘delta D’ content
. Deuterium, or delta D, stands for the relative proportion of two types of hydrogen (
2
H: 1
H). Changes in the proportion of these two types of hydrogen in ice-water correlate to the amount of evaporation and the temperature of the atmosphere. In the next column, paleo-temperatures at Vostok are calculated based on the formula describing the empirical relationship between temperature and deuterium concentration: Temperature (in degrees C) = -55.5 + (delta D + 440) / 6 1.
Begin with the temperature data, and examine Graph E
. Keep in mind that the x axis refers to how many years ago; so the years go up as you go back in time. This is the custom for research that investigates patterns over long time periods. Describe in words how Antarctic temperature has changed over the last 420,000 years. Many glacial and interglacial periods.
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GEOL 121 Global Climate Change Lab 7 2.
On this graph, the colder times correspond to glacial periods (ice ages) and the warmer times correspond to interglacial periods. a.
Are we currently in a glacial or interglacial period? Interglacial b.
Approximately, how long does a glacial and interglacial period last? i.
Glacial: 36000 years ii.
Interglacial: 36000 years
3.
On Graph F
a trend line has been added to the ice core temperature data (black dashed line). Take a look at the R
2
value. Do you think this line is a good representation of long-term rates of temperature change? Yes, the average only is shown, which gives a realistic look into the change 4.
The next step is to calculate what the fastest rate of change might be. To do this, you want to identify a section of your data where the temperature is changing very rapidly. If you hover your mouse over a data point, it will tell you the data values for that particular point. What are the data point values at the beginning and end of the time period segments that you think have the steepest slopes: 120000-0 years
GEOL 121 Global Climate Change Lab 8 5.
The time periods with the greatest rate of temperature change tend to be at the end of the glacial periods. These are call deglaciations. The red solid line and the blue solid line on Graph F are trend lines fit to the data during the two most recent deglaciations. (Note that the slopes of these lines are negative because the time on this graph increases as we go back in time.) What are the rates of pre-historic temperature change (with units) during each of these deglaciations? -.0012 c/year (blue) and -.001 c/year (red) 6.
How do these rates of temperature change compare to what you found for the recent global temperature in Activity A? The temperature change slope is greater than the slope in activity A. Now move to the Vostok ice core CO
2
data 7.
Examine Graph G
. This is a plot of CO
2
concentration as a function of (gas) age. Describe in words how CO
2
has changed over the last 420,000 years. CO2 has a negative slope over glacial periods, currently it is positive though.
GEOL 121 Global Climate Change Lab 9 8.
According to the CO
2
data from ice cores, during which time frame(s) was there the greatest rate of change in atmospheric CO
2
concentration? How does this change in atmospheric CO
2
concentration correspond to what you see in the ice-core temperature record? From 20000 years before present until present is the greatest change in CO2 concentration. As CO2 concentration increases the temperature does as well. 9.
How do the CO
2
concentrations recorded over time in the ice core compare to the current values for today, which you can see in the Mauna Loa data? There is a positive slope indicating increasing CO2 concentration. 10.
Linear trendlines have been added to the Vostok CO
2
data in Graph H
. The black dashed line includes all of the data. The red and blue solid lines just include the two most recent deglaciations (same time periods that we included for the Antarctic temperature). What are the rates of pre-historic atmospheric CO
2
change (with units) for the two deglaciations: -.0101 ppm/year (blue) and -.0104x ppm/year(red) 11.
How do these natural rates of change compare with the modern rate of change? How do current (i.e., in the past ~200 years) changes in atmospheric CO
2
concentration and average global temperature compare to pre-historic (i.e., in the past hundreds of thousands of years) changes in these variables? What does this suggest about whether recent changes in temperature are due to natural or anthropogenic (human) factors? It is plausible that recent increase in atmospheric carbon dioxide is a result of natural fluctuations and not human-induced? The changes in CO2 concentration and average global temperature are bigger and faster than the ones observed in pre-historic changes. It is plausible that the increase in atmospheric carbon dioxide is human-induced and not natural fluctuations.
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GEOL 121 Global Climate Change Lab 10 12.
If atmospheric CO
2
concentrations continue to rise in the future, how would you expect global temperatures to change? Global temperatures are going to be warming. 13.
What is still unclear about changing global temperatures and the relationship between atmospheric CO
2
and global temperature? What questions do you have? N/A