Geographic Perspectives on Earth System Science
Geography 210
Assignment #3: Observed Global Temperature Change
Due via Canvas Friday March, 7 at 11:59 pm
Goal: The goal of this assignment is to quantitatively assess instrumental (i.e., observed) records of global temperatures. You will download and collate data into Excel for analysis, make two plots, and assess trends using Excel’s =SLOPE function. You should plan to download the full version of Excel to your computer or work in a computer lab that has Excel installed. Using the web version of Excel (or Google sheets) may be possible, but the instructions included here pertain to the desktop version of Excel. Read all instructions carefully!
You are responsible for two deliverables to be uploaded to Canvas:
1. A PDF document with the written answers and your plots. To get your plots into your writeup, you can simply right-click it in Excel, select Copy, and paste it into a Word document (by right-clicking or Edit->Paste).
2. Your Excel workbook where you’ve assembled the data, created the plots, and done any other calculations. Name this LastName_TempData_GEOG210_A3.xlsx. Submissions not including an Excel file that includes the analysis shown in the writeup will be penalized 50%.
Specific objectives:
• To obtain and analyze observed temperatures.
• To assess trends in data by calculating linear slopes.
Global mean temperature
Global mean temperature datasets are assembled by multiple scientific agencies using air and ocean temperature observations collected from across the world. In the United States, NASA’s Goddard Institute of Space Studies (GISS) and the National Oceanographic and Atmospheric Administration (NOAA) both compile important global temperature datasets. Similar datasets come from international groups including the Japan Meteorological Agency and the UK’s Hadley Center Climate Research Unit (HadCRU). More recently, a group in the US called Berkeley Earth began creating their own independent global temperature record, initially motivated by their founder’s climate change skepticism.
Step A: Download global temperature data
The first part of this assignment has you download, plot, and investigate the global temperature datasets yourself. For simplicity let’s just work with the NASA GISS, HadCRU, and Berkeley Earth data. Download each dataset as a csv (comma separated values) text file (you may need to right click and choose “save as” to do this).
NASA GISS data:
https://data.giss.nasa.gov/gistemp/
• Download: Combined Land-Surface Air and Sea-Surface Water Temperature Anomalies (Land-Ocean Temperature Index, LOTI) “Global-mean monthly, seasonal, and annual means” data.
• Important: get the CSV (comma separate values) file. Once downloaded, it can be opened directly by Excel!
UK Met Office/HadCRUTv5 data:
https://www.metoffice.gov.uk/hadobs/hadcrut5/data/HadCRUT.5.0.2.0/download.html
• Download: HadCRUT5 analysis time series: ensemble means and uncertainties -> global (NH+SH)/2 -> Annual data (CSV).
Berkeley Earth data:
http://berkeleyearth.org/data/ [GET FROM CANVAS – see below]
• Since the data are provided in a plain text file, it would take a few extra steps to get the data into Excel. Given this, we’ve converted them to CSV to make it easier for you – download the data from Canvas!
• Note that the original data are the: Global Time Series Data -> Global Monthly Averages
(1850 – Recent) -> annual summary (of the Monthly Global Average Temperature). This data file has a “header” that describes the data and the columns. In our analysis, we want to use the “Land + Ocean data using air temperatures above sea ice” data.
Step B: Collate the data into a single Excel workbook
Now that you’ve downloaded the three files containing the data, we will want to bring them into a single Excel workbook, but under separate worksheets (tabs). Make sure to label your tabs, so you know which dataset is which!
NASA GISS data:
• Double click the GLB.Ts+dSST.csv NASA GISS data file to open it in Excel. Immediately after opening save the notebook as an Excel Workbook (.xlsx) file (this is critical!). Name it
LastName_TempData_GEOG210_A3.xlsx.
• Rename the tab (aka worksheet) to “NASA GISS” by double clicking on the tab in the lower left.
HadCRUTv5 data:
• Double click the HadCRUT.5.0.2.0.analysis.summary_series.global.annual.csv file, which will open it in another Excel window.
• Let’s move this to the other workbook, by right clicking the tab at the bottom left and
clicking Move or Copy. In the “To book” select your LastName_TempData_GEOG210_A3.xlsx file, then click OK.
• Rename the tab to “ HadCRUT.5” by double clicking on the tab in the lower left.
Berkeley Earth data:
• Double-click the BerkeleyEarth_Feb2025.csv file, which should open in another Excel window.
• As with the HadCRUT data, let’s move this to our main workbook. Right click the tab at the bottom left and click Move or Copy. In the “To book” select your
Lastname_TempData_Lab5.xlsx file, then click OK.
• Rename the tab to BerkeleyEarth.
When all datasets are in the same Excel workbook, you’ll have three worksheet tabs that looks something like:
Step C: Analyzing global temperature data
Question 1 [20 pts]:
Create a single plot including all three datasets. Tip: the type of chart you’ll want to use a scatter plot with straight lines. Plot time along the x-axis and temperature along they-axis. Label your y-axis, limit your x-axis from 1840 to 2030, and set the major units to 20. Click they-axis and specify that the horizontal axis crosses at the minimum value on your y-axis (this places the x-axis at the bottom of the chart). Add a legend with appropriate names for the datasets you’ve plotted.
The data to plot are:
• NASA GISS: J-D (Jan-Dec average temp anomaly; Column N) over 1880-2024
• HadCRUTv5: Anomaly (degC) (Column B) over 1850-2024
• BerkeleyEarth: Annual Anomaly (Column B) over 1950-2024
Hints to get you started:
• Start in the NASA GISS tab. Select 1880-2024, then select the corresponding temps in the J- D column (note you’ll need to skip the last value as it’s for 2025 and incomplete!).
• Once the data (not the full columns!) are selected, go to the tab Insert -> Scatter -> Scatter with straight lines. This will plot the data!
• Next, right click the plot and click “Select Data … ”
• Give Series 1 a better name: NASA GISS
• Click the +
• Type a name for the dataset (HadCRUTv5)
• Click the button in right of the X values box to select data:
• Click to the HadCRUTv5 tab and select the rows with the years.
• Now clear out the ={1} in the Y values field, and select the corresponding temperature data for HadCRUTv5.
• Do the same for Berkeley Earth now!
• For full credit, tidy up your plot following the instructions in (a) above!
Question 2 [5 pts]:
Describe (qualitatively – in words) how the three datasets compare. Is there a consensus of how global temperature has changed over this time period?
Question 3 [10 pts]:
What are the annual trends in temperature from each dataset between 1970 and 2024? Use Excel’s SLOPE function (=SLOPE(known_y's, known_x's)) to calculate linear trends in the data.
• For theY data, use the temperature data. For X, use the years.
• The slopes are in °C/year.
• What are the decadal trends from each dataset? (Hint: you’ll need to multiply yearly trends by 10 to get the decadal trends).
• Again, how do these numbers compare between the datasets?
Question 4 [10 pts]:
Create a copy of the BerkeleyEarth worksheet by right clicking the tab, selecting “Move or Copy”
and checking the “Create a copy” check box. Clear the extra columns of data so you just have two columns: year and annual temperature anomaly. What are the 10 hottest years on record? What are the 10 coldest years on record?
Use Excel’s sort function to find hottest and coldest years:
• Select the temperature data, then use the Sort & Filter tool in the Home tab:
Be sure to tell it to expand the selection (this will reorder the years column as well):
Question 5 [5 pts]:
Based on your analysis, what would you say to someone that says the world is not warming? [5 pts]