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Graphs in Environmental Science

Graphs in Environmental Science

Author: Sophia Tutorial
Description:

Recognize the design element for a misleading graph.

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Tutorial

what's covered
In this tutorial, we're going to cover the topic of graphs in environmental science. Today's lesson will cover four different examples of graphs that are used in environmental science, though there are more that will not be discussed here. We will also explore how graphs can be manipulated to present false or misleading information, and discuss examples of environmental photos and their purpose.

Our discussion breaks down as follows:

  1. Examples of Graphs in Environmental Science
    1. Line and Bar Graph Combination
    2. Line Graph
    3. Scatter Plot
    4. Pie Chart
    5. Bar Graph vs. Area Chart
  2. How Graphs Can Be Misleading
  3. Use of Photography


1. Examples of Graphs in Environmental Science

As mentioned above, we're going to explore four different examples of graphs that are used in environmental science. Each graph will be paired with a verbal equivalent of what the graph is communicating.

1a. Line and Bar Graph Combination

For example, this first chart communicates that Edinburgh, Scotland's capital, has a mean peak maximum temperature of about 19 degrees Celsius in the month of July, and a low mean minimum temperature of about zero degrees Celsius in the month of February. The line and bar chart combination, shown below, are the visual representation of this information.

Edinburgh Climate

The title of the graph is "Edinburgh Climate." As shown at the bottom, the legend explains that the red line graph is for mean daily maximum temperature, and the blue line is mean daily minimum temperature. The x-axis indicates time with the months of the year, while the y-axis indicates temperature in Celsius on the left. This graph also shows precipitation in Edinburgh year-round in millimeters on the right, making for a second y-axis.

1b. Line Graph

The next graph is of an ice core sample taken from Vostok, Antarctica. It shows multiple things, one of which is that the Earth has had multiple peaks in temperature and CO2 concentrations in the atmosphere over the last 400,000 years.

Vostok Antarctica Ice Core

Looking at the graph, you can see the title, "Vostok Antarctica Ice Core," at the top. There is no legend in this line chart, but the x-axis shows time in thousands of years, starting at the making of the graph and going back 400,000 years. There are three y-axes showing three separate units: dust in parts per million, carbon dioxide concentration in parts per million by volume, and change in temperature in degrees Celsius. The graph shows a cycle of rises and falls in temperature, CO2, and dust over the last 400,000 years.

1c. Scatter Plot

Next we're going to look at a visual chart first, and then examine a written representation of it. The title of the scatter plot below explains that this chart is about particulate matter pollution of a certain size, that was recorded as a daily mean concentration for Kern County, California. The x-axis shows time from the year 2001 to 2010, with a data point for every day of the year. The y-axis shows the particulate matter concentration measured at 2.5 micrograms per cubic meter. Note that the majority of data points fall below 20, but spike seasonally.

Pollution Graph

A written version would look something like this:
Kern County, California's daily mean particulate matter, at 2.5 micrograms per cubic meter, from 2001 to 2010, had the vast majority of days at or below 20. There is a seasonal variation in the middle of the year, where a spike occurs.

1d. Pie Chart
Let's do one more like this. The title of the chart below is "Annual world greenhouse gas emissions, in 2005, by sector." This pie chart doesn't have any axes or legend, but its subdivisions are separated by sector. As you can see, certain sections take the majority of the pie, while a few others make up the last small bit.

Pie Chart Greenhouse Gas Emissions

A textual version might look something like this:
In 2005, the majority of greenhouse gas emissions came from the electricity and heat sector, followed closely by Industry and Transportation. A few other sectors produced as well, but were only minor emitters.

1e. Bar Graph vs. Area Chart

In our last example, we're going to look at two different graph types presenting the same information. The first one is a bar graph of a fictional region. The title "Fictional Region Precipitation" is at the top of the graph. The legend indicates that the bar chart and its color represent rainfall. The x-axis represents units of time in years from 2012 to 2014. The y-axis represents rainfall in millimeters. From this graph, it can be concluded that the year with the highest amount of precipitation was 2014.

Region Precipitation

Next is a different chart called an area chart, using the same data. Once again, you can see the title indicating that this is a graph about rainfall in a fictional region. The legend is the same as the last. The x-axis is the same, and the y-axis is also the same. However, the data points are represented as shaded-in sections of the graph underneath them. This makes the graph look different, even though it is the same information. Despite appearances, the same conclusions can be drawn: 2014 had the highest precipitation in millimeters.

Region Precipitation


2. How Graphs Can Be Misleading

Now we're going to discuss how graphs can be misleading. Common ways that graphs mislead viewers are:

  • Using a manipulated scale that doesn't begin at zero
  • Using a title that is misrepresenting
  • Using uneven increments on an axis
  • Creating a gap in the scale
  • Using a 3D or confusing design to mislead viewers

EXAMPLE

Consider the graph below. It is a made-up graph about a fictional corporation's sulfur dioxide emissions over time. The graph appears to indicate that the company's emissions are going down. However, there's a gap in the scale. The graph only shows data from the years 2010, 2012, 2014, and 2015. The years 2011 and 2013 are entirely missing. This can mislead the viewer's conclusion.

Now let's look at what the graph is like with those two years included. You can see that 2011 was the same as 2010, and 2013 was higher than all the rest. This graph provides a more accurate picture of what the fictional corporation's sulfur dioxide emissions look like from year to year.

Sulfur Dioxide Emissions


3. Use of Photography

Photography can be used to convey information and generate emotions. Photography of environmental science issues, like the image below of trash collecting in a large jumble in the middle of the Pacific Ocean, can convey information on environmental science topics, such as oceanic waste.

Ocean

However, it is not necessarily a purely scientific endeavor. This photo may also have been taken with the purpose of generating feelings of sadness, guilt, or ecological stewardship. The goal of the photo may have been to encourage better ecological behavior, such as recycling, or regulation on ocean waste dumping.

hint
Always remember what platform you are consuming scientific information from, and what biases might be incorporated, depending on the source — be it a scientific journal, an environmentalist magazine, a political source, or popular media.


summary
We discussed several examples of graphs used in environmental science, and how graphs can be designed to be misleading. We also learned about how environmental photos can convey both information and emotion.

Source: Adapted from Sophia instructor Jensen Morgan, EDINBURGH PD HTTP://BIT.LY/17VSLGB ICE CORE CC HTTP://BIT.LY/1WYDLXV CALIFORNIA PM CC HTTP://BIT.LY/1WJE9AY PIE CHART CC HTTP://BIT.LY/1DYNG6D CHART TOOL CC HTTP://BIT.LY/1BUNHIZ DEFORESTATION, PD HTTP://BIT.LY/1CI1X9N OCEAN TRASH CC HTTP://BIT.LY/1DYPKDY