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Broken Line Graphs - Answer Key

Analyzing Global Greenhouse Gas Emission Rates in Broken-Line Graphs


Analyzing Global Greenhouse Gas Emissions Rates in Broken-Line Graphs


  • Broken-line graph

Student Exploration

Who monitors pollution across the Earth? How can you use broken-line graphs to analyze the greenhouse gas emissions of different countries?

The United Nations Framework Convention on Climate Change (UNFCCC) is an international environmental treaty, also known as the Earth Summit, which meets to try and stabilize the greenhouse gases (GHG) emitted globally. GHG are emitted every time we burn fossil fuels to power our homes, cars or to make the items we consume, causing carbon dioxide to be emitted up into the atmosphere.

Examine their report on the GHG emission profiles of countries across the global at the website below. Choose your own country and one other country and compare the total GHG in the broken-line graph of your country and the second country.


Image of a power plant.

Answers will vary based on the countries that students choose, or they could be assigned different countries by their teacher. This example compares the GHG emission profiles of the United States and the Czech Republic.

The United States GHG emissions are much higher than those of the Czech Republic. In the last twenty years the GHG emissions of the United States have overall increased at a slow and constant rate. They have been between the CO_2 levels of 6,000,000 and 7,200,00. The rates increased at and slow and constant rate from the years of 1991 to 2007, expect in the years of 2001 and 2006 when there were slight decreases. In the years of 2008 and 2009 the emission decreased relatively significantly. But then in 2010, emissions rose again to just under 7,000,00.

The GHG emissions in the Czech Republic were at their highest in 1990 at just under the 200,000 Gg CO_2 level. Overall since 1990, the GHG emissions in the Czech Republic have decreased. There have been a few years when they increased slightly, such as in 1996, 2000 and 2003. In 2009 the emission were at their lowest, at approximately 140,000.

Extension Investigation

Answer the following questions about the two countries you chose:

  1. In what year were the GHG emissions the highest?
  2. In what year were the GHG emissions the lowest?
  3. How have the GHG emissions changed from 1990 to 2010?
  4. What can you conclude about the GHG emissions of the two countries?
  5. What is another type of graph that would be useful for representing this data? Explain why it would be useful.

Resources Cited


Connections to other CK-12 Subject Areas

  • Basic Graph Types
  • Energy Conservation
  • Introduction to Energy Resources

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