3.1: Climate Data

Climate At A Glance

Numerous weather and climate data, including observations of temperature, wind, air pressure, and precipitation, make up the climate record, and climatologists are particularly interested in these variables to describe a location’s climate. In the United States, Climatologists can access the NCEI Climate at a Glance (CAG) website to access and analyze real-time or near-real-time recorded data. You can access the CAG website: Climate At A Glance. For many of the activities we’ll do in this investigation, the data and any plots will be given to you, but it is still a worthwhile skill to explore the CAG website and pull up climate data for a location.

To do so, do the following:

1. Go to the Climate At A Glance website.
2. In the tabs at the top, click “Nation,” then under “Time Series,” click “Launch.”
3. The National Time Series page has five drop-down menus near the top that let you change settings for the parameter (variable), time scale, month, start year, and end year.
   1. Under Timescale, click the dropdown menu, select “12 months,” then under month, select “December.”
   2. You shouldn’t need to change anything else. Before proceeding, make sure the parameter is set to “Average Temperature” and that the start and end years are 1895 and 2026, respectively. This will give you annual temperature averages for the United States from 1895 to 2026.
4. Under the "Base Period" and "Trend" menus, click on both the "display base period" and “display trend" checkboxes.
5. Hit Plot. You should now see a time series of Annual Average Temperatures for the United States for the 12-month period ending in December.

Questions based on above procedure

Let’s start answering some questions based on this plot:

1. The 20th-century (1901-2000) temperature average (mean) for the United States was approximately:
   1. 51.09℉
   2. 49.37℉
   3. 52.01℉
   4. 53.36℉

The blue trend line shows how temperatures are trending over time. Trend lines are useful for identifying a discernible trend in the data. When a line slopes upwards as it moves right, that indicates a warming trend; when it slopes downwards, a cooling trend.

2. Average temperature data from the United States show that temperatures are experiencing a _________ trend.
   1. warming
   2. no
   3. cooling
3. This indicates that, if the trend were to continue, we could expect temperatures in the United States to __________ in the next several decades.
   1. level off
   2. begin falling
   3. keep rising
4. Hover your cursor over the time series to see individual years (which will appear as a vertical line in the time series with an average temperature at the bottom of the line). You could also scroll down and view the data presented in the table below the chart. The last time an individual year was BELOW the 20th century average was:
   1. 1976
   2. 1996
   3. 1989
   4. 2020

Now let’s look at the US Precipitation data.

• Scroll back up to the top of the page, where the drop-down menus were.
• Under the dropdown menu next to “Parameter,” select “Precipitation.”
• Keep Everything else the same. Hit “Plot.”

Now you should see a time series with an average, trend, and individual years for precipitation in inches and millimeters. Scrolling down further, you can see the same data in table form.

5. The 20th average precipitation for the United States is ______ inches.
   1. 30.37”
   2. 28.74”
   3. 31.39”
   4. 29.92”
6. Based on the per-decade trend, the United States is, on average, becoming:
   1. Wetter
   2. Drier
   3. Neither Wetter or Drier.
7. Based on your analysis of the last two charts, the United States is, on average, becoming:
   1. Colder and drier
   2. Colder and wetter
   3. Warmer and drier
   4. Warmer and wetter

The NCEI CAG website also contains data for individual regions and even cities. Let’s examine California specifically.

• Scroll back up to the top of the page, where you can see the “National Time Series” title. Above that, there should be a menu with options such as “Global,” “Nation,” “Region,” “State,” etc. Hover over “State” and select “Statewide Time Series.”
• You’ll see a page similar to the National Time Series page, but with an extra box for State.
• Select “Average Temperature” as your parameter, “12-Month” as your time scale, 1895 and 2025 as your start/end times respectively, and California as your State. Then press “Plot”.
• Make sure you click the "display base period" and “display trend" checkboxes again.

You should now see a very similar time series to what you saw for the United States, but now for California.

8. The 20th-century average temperature for California is a bit warmer than the United States average (makes sense since California is in one of the warmer climates of the country), with an average of:
   1. 57.4℉
   2. 59.37℉
   3. 55.32℉
   4. 56.18℉
9. Look at the trend line and the calculated trend, which you can see in the upper-right of the graph. The plotted trend line and the calculated trend show that California is:
   1. Getting cooler
   2. Not changing much
   3. Getting warmer.
10. Now scroll up to the dropdown menus again and change the parameter to “Precipitation” and click “Plot.” Based on the Time series for average precipitation, California’s wettest year was:
    1. 1998
    2. 2015
    3. 2023
    4. 1983
11. Based on the plotted and calculated trend, California is getting:
    1. Drier
    2. Wetter
    3. Experiencing little to no change in average precipitation