Solving the Carbon Dioxide Problem

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Students use information from Project Drawdown to learn about the sectors where climate solutions are being implemented to help slow down climate warming. Students construct a plan for using specific solutions to reduce and remove the amount of carbon dioxide in the atmosphere, and make a claim describing how their plan could work to keep global temperature change below 1.5 °C .

Learning Goals

  • Students will analyze the sources and sinks of carbon dioxide in the atmosphere to determine the complexity and uncover questions.
  • Students will investigate and evaluate current solutions for reducing the amount of carbon dioxide in the atmosphere
  • Students will propose a plan to use viable mitigation strategies for meeting the demand of reducing atmospheric carbon dioxide and consider the challenges associated with each strategy
  • Students will make a claim, supported by evidence and reasoning, as to how their plan will remove enough carbon dioxide from the atmosphere to limit global warming to 1.5 °C.



  • Students will benefit from having some knowledge of the carbon cycle and the role of carbon dioxide emissions in climate change. Plan to have a discussion or lesson to introduce these ideas before beginning this activity.
  • Plan for student grouping arrangements in advance. In Part 1, six groups of students are needed; each group will focus on analyzing a different sector. In Part 2, it might be best to create new groups that contain one student from each of the sector groups from Part 1.


Part I: Uncovering the Parts, Purposes, and Complexities of Reducing Carbon Dioxide in the Atmosphere (70 minutes)

  1. Ask students to think about the challenge of slowing climate warming by reducing the amount of carbon dioxide in the atmosphere. How would we get started? What actions would we need to take as a society?
  2. Share the diagram (below) of sources and sinks of carbon dioxide with your students. The diagram is accessible as a PDF and as slide image from the Materials list above.
    • Ask students to share observations from this diagram. What do you notice? What do you wonder about? (They might notice that there are more sources than sinks, that more than half of the carbon dioxide that enters the atmosphere is staying there, that some sources are adding more carbon dioxide than others, etc.)
    • Make connections between student wonderings and previous experiences your class has had about the carbon cycle and carbon dioxide sources/sinks.

This is a diagram showing the current sources of carbon emissions into the atmosphere: 25% electricity production; 24%food, agriculture, and land use; 21% industry; 14% transportation; 6% buildings; and 10% other energy related emissions. It also shows current carbon dioxide sinks: 24% land sinks, 17% coastal & ocean sinks. 59% of the carbon dioxide added to the atmosphere remains in the atmosphere.

  1. Tell students that to address climate change, we need to transform the way humans impact the world in each of these different areas, or sectors, that we see in the diagram, and focus on reductions and removals:
    • reducing greenhouse gases and sources of carbon dioxide entering the atmosphere
    • increasing sinks to remove carbon dioxide from the atmosphere
    • improving society through education and health (not shown as part of the diagram, but an important cross-cutting component).
  2. Tell students that coming up with solutions to reduce and remove carbon dioxide within each sector is complex, but not impossible. Share the quote from Project Drawdown: “Almost daily, there is promising evolution and acceleration of climate solutions.”
  3. Create six groups in your classroom, and assign each group to analyze a different sector from the diagram, using information from the Project Drawdown- Sectors webpages:
    • Electricity Production
    • Food, Agriculture, and Land Use
    • Industry
    • Transportation
    • Buildings
    • Sinks: Land, Coastal & Ocean, Engineered

Note: you could split Sinks into two groups if needed, making land sinks its own group and coastal, ocean and engineered sinks another group.

  1. Tell each group that their task is to analyze their sector and come up with a way to share information about its parts, purposes, and complexities with the class. Reading about their assigned sector linked from the Project Drawdown- Sectors webpages, they should find both a description of how the sector is contributing to climate change, as well as many different solutions that are linked to each sector. Groups should organize their analysis as a visual presentation (for example: a chart, diagram, or slides). Give each group copies of the Sector Analysis Planning Sheet to use as a place to capture and organize their thinking.
    • Parts: Define the components of this sector. How does the sector contribute to the problem of climate change? In what different areas are solutions needed? Provide information to help us really understand this sector and how to address it. Include data where possible.
    • Purposes: Explain how addressing different parts of this sector will help reduce atmospheric carbon dioxide. What is their role? Provide 1-2 examples of the type of solutions that are currently being implemented in this sector, and explain how they will help. 
    • Complexities: What are the challenges with implementing solutions to this sector? What further developments are needed to make reducing atmospheric carbon dioxide in this sector successful? What questions do you have?

Sector Analysis Example (for teacher reference)

Sector - Electricity *Note: most all of this information can be found on the Project Drawdown website.

PARTS: Many parts of our everyday lives (if you live in a developed or developing nation) require electricity, from our homes to transportation, work, and manufacturing of goods and services. Most electricity today is created by burning fossil fuels, which releases lots of carbon dioxide in the atmosphere. About 25% of greenhouse gas emissions comes from generating electricity. Climate solutions are needed in the following areas: we need to enhance the efficiency of things that use electricity, we need to shift the production of electricity from fossil fuels to renewable energy, and we need to improve technologies for transmitting and storing electricity so that renewable energy supply can meet demand.

PURPOSES: Enhancing energy efficiency in buildings and industry will decrease the amount of electricity that needs to be generated. Buildings and industry are the largest users of electricity, so decreasing their energy draw will decrease the amount of fossil fuels that are burned at the power plants. Using alternative energy sources like wind, solar, water, or even nuclear will allow us to move away from burning fossil fuels for electricity, which will drastically decrease the amount of carbon dioxide that is entering the atmosphere. Upgrading our entire electricity system will allow us to use electricity generated from alternative sources better. Advancements in storing energy from the Sun and wind will make these energy sources available even when Sun and wind are not present. Examples of ways to improve efficiency are adding insulation and using LED lighting. And installing micro wind turbines provides a clean source of electricity to rural areas without access to a centralized grid.

COMPLEXITIES: Efforts to transfer electricity production away from fossil fuels need to increase so that this can happen on a much shorter timeline. And it is challenging to provide equal access to electricity solutions to everyone. The technology to improve energy storage is underway, but it is not yet usable on a global scale. It seems uncertain if every community will be able to afford the new technologies that are needed to shift away from fossil fuels. Possible questions: How much of an impact does improving energy efficiency in my home make? How can we speed up the transition away from fossil fuels? What is a bigger obstacle-- cost or innovation (ie, do we have the technology but lack the funds, or do we still have a long way to go to invent the technology)?

  1. Have students spend the remainder of the class period developing their parts-purposes-complexities analysis and creating their visual aid.
    • Students will be successful finding most all of the information to complete this part of the assignment from the Project Drawdown- Sectors webpages, but encourage them to research further (from reliable sources!) as needed and to spend time learning about any terms or concepts they encounter along the way that are unfamiliar to them.
  2. At the beginning of the next class period, have students present their sector analyses as a gallery walk, or as group presentations. Spend about 20 minutes before moving on to Part 2.

Part II: Exploring Solutions (80 minutes)

  1. Transition to the second part of the activity. Share with students that they will now make a plan for climate solutions based on their new understanding of the sectors.
    • Even if we could reduce carbon dioxide emissions to zero immediately, the climate has already warmed about 1 °C above what it was in pre-industrial times, and will continue to warm for many years.
    • Thus, to prevent environmental changes that will be extremely difficult to adapt to, scientists have determined that we must limit global temperature increase to 1.5°C (which means only 0.5°C more in warming).
  2. Present the challenge: Even with rapid emissions reductions, the world will need to remove about 10 gigatons of CO2 from the atmosphere every year by mid-century and 20 gigatons of CO2 per year by 2100. (Source: National Academies of Sciences, Engineering, and Medicine)
  3. As a class, calculate how much carbon dioxide (in gigatons) must be removed from the atmosphere by 2100.
    • Use 2050 as "mid-century" and assume that carbon removal ramps up steadily from 10GtC/year in 2050 to 20 GtC/year in 2100.
    • Example: Starting from the year 2020, we need to remove 300 GtC by 2050 (at a rate 10 GtC/year). From 2050-2100, we need to remove an additional 751.2 GtC, which means an extra 0.2 GtC each year to ramp up to 20 GtC/year by 2100. This means we need to remove a total of 1051.2 GtC between 2020-2100.
    • For the purposes of this activity, we will use removal of 1000 GtC by 2100 as our target goal. You may choose to use the exact value calculated, adjust the directions accordingly if so.
    • Optional: To help students conceptualize the amount of carbon dioxide that must be removed, consider a brief units review:
      • GtC = gigatons of carbon; 1 gigaton = 1 billion metric tons; a metric ton = 1000 kilograms or 2204.6 pounds (an English system ton is 2000 pounds).
      • Have students calculate how many kilograms or pounds are equal to 1000 GtC.
  4. Share the diagram for staying below 1.5 °C of global warming (below) with students. Spend a few minutes having students discuss the following prompts with a partner while examining the diagram:
    • About how much carbon dioxide are we currently adding to the atmosphere each year? (about 40 Gt/yr)
    • What is significant about 2050, according to the diagram? Explain. (2050 is the target to reach net-zero carbon dioxide emissions, which means human activities are no longer increasing the amount of carbon dioxide that is in the atmosphere. Mitigation and carbon removal actions are needed to make this happen.)
    • Why are negative emissions needed in the future? (Because we are already experiencing climate warming due to increasing the amount of carbon dioxide in the atmosphere, it is not enough to stop adding carbon. We must also remove the excess carbon dioxide from the atmosphere to slow down climate warming.)
    • Why is the conventional mitigation techniques (blue) part of the plan so much larger than the carbon removal approaches (green) part? (Mitigation, or reducing the amount of carbon dioxide that we are adding to the atmosphere, is the biggest priority right now. Carbon dioxide removal is important too, but large-scale carbon removal requires technologies that are not widely available at this time. To get to net-zero, wide-scale mitigation solutions are needed.)
  5. Have some students share out from their partner discussions, making sure that the class understands the diagram before moving on.
    • Discuss terms used in the diagram, such as "net-zero" and "negative emissions" to ensure common understanding.
    • Point out that in 2018, global carbon dioxide emissions totaled 37 billion tons, which is a value that might be helpful in the next steps as students begin to construct their plan.

This is a diagram that shows the amount of carbon dioxide reduction needed to get to net-zero carbon emissions, and the additional carbon dioxide removal that is needed beyond the reductions to keep global warming below 1.5 degrees Celcius.

  1. Tell students that they are going to work with a group to create a plan for how to meet the challenge of removing 1000 GtC from the atmosphere by 2100. Their plan will include a combination of many different solutions. Tell students that they will present their plan to the class.
    • Rather than having students return to their group from the day before, it might be best to create new groups that contain one student from each of the sectors (E.g. one student who was in the electricity group; one from the Food, Agriculture, & Land Use group; one from the Industry group; one from the Transportation group; one from the Buildings group; and one from the Sinks group).
  2. Return to the Project Drawdown website, this time focusing on the specific solutions for each sector.
    • Orient students to the website, showing them that each solution can be accessed from the Solutions page, and also in the Table of Solutions. From the table, solutions can be sorted by sector, which might be helpful. Students should focus on carbon dioxide removal values from the Scenario 2 column, which aligns with the 1.5 °C goal. Scenario 1 values align with the 2 °C goal. Note: The Paris Agreement of 2015 set the goal of keeping global temperature increase below 2 °C, while also striving to meet the 1.5 °C goal, which is why both scenarios are presented.
    • Point out that the solutions are based on a "reasonable yet optimistic" forecast for how the solution will be enacted in the future. Thus, it is important to consider a range of potential impacts from each solution.
    • Choose one solution to look at together as an example, pointing out the various information that can be found (carbon dioxide reduction value, cost, description, etc.) and also the Technical Summary link, which often contains more information than is needed for the assignment, but could be helpful when thinking about limitations and other details.
  3. Point out that the carbon dioxide reduction values provided for each solution only get us to 2050, so students will need to make a plan to get us to a reduction of 1000 GtC by 2100 using their best estimations for carbon reduction between 2050 and 2100.
    • Students should consider the Staying Below 1.5 Degrees of Global Warming diagram as well, to help them approximate the proportion of carbon dioxide emissions reduction to carbon dioxide removal approaches that might work best.
    • There are more potential solutions than are provided on the Project Drawdown website. In fact, more innovations come about all the time. Encourage students to research additional ideas about solutions if they desire, but remind them that they will need to make sure there is a way to include how much carbon dioxide will be saved from any solution they include. Have students brainstorm how they could include solutions that they cannot quantify in their plan (perhaps as a section about possibilities for the future, for example).
  4. Give each group copies of Carbon Dioxide Solutions: Plan Guide to use as they develop their plan. Explain that each group will construct a visual way to share their plan with the rest of the class as part of their presentation (for example: a chart or diagram on a poster or slides). Their plan should include:
    • A Claim that explains their plan for reducing atmospheric carbon dioxide by 1000 Gigatons by 2100. A diagram that walks us through their plan may be helpful here.
    • Evidence, such as the mathematical explanation for the plan, and information about each solution that is part of the plan. For each solution:
      • Name and briefly describe how it reduces the amount of carbon dioxide in the atmosphere.
      • What sector does it address?
      • How much carbon dioxide can it remove by 2050?
      • How much does it cost to implement and/or maintain?
      • What, if any, limitations are there to this solution?
      • Are there places that the solution might work better than others, or will it likely work well anywhere on Earth? Why? (E.g., consider how ecological, economic, political, or social conditions might affect how well the solution works in a particular area.)
    • Reasoning that justifies their climate solution choices. In the reasoning, they should also mention any questions that remain unanswered or limitations to their plan.
  5. Give students the remainder of the second class period, and the entire third class period, to work on their plan within their groups.
    • Provide students access to Internet-enabled devices and the link to the Project Drawdown Solutions website.
    • Students might find it helpful to use sticky notes and/or chart paper as they design their plans.
    • Discuss additional supplies needed for group presentations, such as poster board, or presentation tools (like Google Slides or PowerPoint).
    • Consider what scaffolds or supports your students might need to be successful during extended group work, such as assigning group roles.

Part III: Sharing Our Plans (50 minutes)

  1. At the beginning of the fourth class period, have students present their plans to the class. Allow time for rich conversations and exchange of ideas between groups. Hopefully, students will be interested in comparing their own plan to those of their peers.
    • If students have made posters to communicate their plans, consider holding a gallery walk, and encouraging 1-2 group members to remain at their group’s poster to answer any questions their classmates might have about their plan. Group members could take turns staying to answer questions and visiting other group’s posters throughout the classroom.
    • Alternatively, each group could present their plan to the entire class one at a time with presentation slides that share their visuals. Encourage questions and answers following each presentation.
  2. Hold a wrap-up discussion, asking students to call out commonalities between plans and any new ideas that came up during the gallery walk. Ask students to share any questions they still have, and to consider the uncertainties, and the opportunities, around climate change solutions.
    • Consider having students rank solutions and discuss why they chose to rank them as they did. You could rank according to: solutions with the greatest impact on carbon dioxide reduction, solutions with the greatest implementation range, or solutions with the greatest likelihood of success.
    • Steer students towards a final concluding idea: there is no one solution to climate change. All of the solutions are needed, including more that we haven’t discovered yet. Climate change solutions will vary from one community to the next, depending on their unique needs and capabilities, but our ability to reach the 1.5 °C goal is greatest when the entire global community participates in finding solutions.


The Carbon Cycle and Climate Change

Most of the carbon on Earth is sequestered in rocks, but it is also stored in the ocean, the atmosphere, soils, and plants. Carbon cycles between the Earth's spheres (geosphere, hydrosphere, biosphere, and atmosphere), sometimes quickly, like when fossil fuels are burned, and sometimes slowly, like when layers of sediment and shells form rock on the ocean floor. The movement of carbon between Earth's spheres is naturally balanced, but human activities since the Industrial Revolution are adding carbon to the atmosphere in a way that is out of balance. Rapid increases in the amount of carbon dioxide entering the atmosphere is causing the climate to warm. The extra carbon dioxide that is added to the atmosphere can remain there for centuries. To put the system back into balance, we must drastically reduce the amount of carbon entering the atmosphere and also remove carbon dioxide from the atmosphere to the other spheres.

Learn more about the carbon cycle:

The Role of Carbon Dioxide in Climate Warming

Carbon enters the atmosphere both through natural processes, such as decomposition or volcanic eruptions and also as a result of human activity, such as burning fossil fuels. Carbon dioxide and methane (CH4) are two types of greenhouse gases that trap energy from the Sun in the atmosphere, which causes the planet to warm. Without any greenhouse gases, the Earth would be too cold to sustain life at current levels, but with the current rapid increase of greenhouse gases, the climate is warming too much. Human-caused carbon emissions have been rising since the 1850s when the Industrial Revolution brought about wide-scale use of combustion engines and the burning of coal for electricity. The concentration of CO2 in the atmosphere is increasing along with the increase in human-caused carbon dioxide emissions, as seen in the graph below.

This is a graph showing carbon dioxide concentration in the atmosphere over the past 800,000 years. Concentrations fluctuate between just below 200 ppm and 300 ppm until we reach the present and levels skyrocket to over 400 ppm.

The warming climate is causing many changes on Earth, such as melting ice sheets, sea level rise due to thermal expansion of ocean waters, and changing weather patterns which lead to drought in some areas and intensified storms in others. As more carbon dioxide enters the water, the oceans are becoming more acidic, which is harmful to marine ecosystems. The effects of increased carbon dioxide in the atmosphere are compounded by feedback loops, in which warming leads to more warming. For example, when warming surface temperatures cause ice sheets to melt, less energy from the Sun is reflected from the darker, ice-free surface, and instead is absorbed, which leads to more warming. Because of these and other types of feedback loops, the effects of adding carbon dioxide to the atmosphere are often compounded.

Learn more about the role of carbon dioxide in climate warming:

Reducing and Removing Greenhouse Gases to Slow Climate Warming

To stop climate change, we need to reduce the amount of greenhouse gases, like carbon dioxide, in the atmosphere. There are two main ways that we can stop the amount of greenhouse gases from increasing: we can stop adding them to the air and we can increase the Earth's ability to pull them out of the air.

This is called climate mitigation. There is not one single way to mitigate climate change. Instead, we will have to piece together many different solutions to stop the climate from warming. Many of these solutions are already being implemented in places around the world. Some can be tackled by individuals, such as reducing energy use, riding a bike instead of driving, driving an electric car, and switching to solar power. Other actions to mitigate climate change involve communities, regions, or nations working together to make changes, such as: switching power plants from burning coal or gas to renewable energy sources, and growing public transit.

Learn more about removing carbon dioxide from the air:

Project Drawdown

Project Drawdown is a non profit research organization that exists as a resource to educate about climate solutions. They help to advance climate actions by reviewing and assessing climate solutions to ensure that communities, businesses, and even governments, are armed with the information they need to implement effective actions. "Drawdown" refers to the time in Earth's future when levels of greenhouse gases in the atmosphere are steadily declining. Many resources, including a download of The Drawdown Review publication, are available from their website at no cost.

Parts, Purposes, and Complexities Routine

The Parts, Purposes, and Complexities routine is one of Harvard’s Project Zero Thinking Routines which provide structure to help make student thinking visible. The Parts, Purposes, and Complexities routine can be used when introducing and exploring ideas to help students think about the complexity of a system or object and is used in this activity as a way to help students analyze the complexity of the different sectors where climate solutions are needed. As with any new classroom practice, the first time students engage with it they may need extra support. There are tips for launching the Parts, Purposes, and Complexities routine with your students provided along with the description of the routine at the link above.


  • Compare the Project Drawdown Table of Solutions rankings for Scenario 1 and Scenario 2 to student rankings created during the wrap-up. Note: you can reorder the solutions on the Drawdown website by sorting the columns of the table.
    • Ask students to consider the following: Project Drawdown is ranking solutions based on their carbon dioxide reduction potential, but what other factors did you consider when making your plan?
    • Have students make a list of the pros and cons of considering other factors (such as cost, unique needs of certain communities, social implications) and not just carbon dioxide reduction.
    • Hold a discussion, using the students' list of pros and cons.

Related Resources

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This activity was developed by Melissa Rummel at the UCAR Center for Science Education.