23: Climate / Energy Pathways 2100

Key questions for this investigation

  • How might global society’s energy production be changed to keep MGT increase to the Paris target of less than 2.0°C?
  • How could energy efficiency be changed to meet this goal?
  • How could carbon sequestration play a role in meeting this goal?

To investigate these questions you will design a pathway for achieving the 2015 Paris goal of keeping the increase in mean annual global temperature (MGT) to less than 2.0°C. To do so you will be using three tools, 1) a graph of world energy consumption and production, 2) a flowchart of global energy flow for 2011, and 3) an online energy / climate model.

Tools used in this investigation


Many proposals for reducing global carbon emissions involve doing one or more of the following…

  • Reducing carbon emissions from energy production.
  • Increasing the efficiency of energy consumption to reduce the amount of energy that needs to be produced to do the work we require.
  • Sequestration – Removing carbon from the atmosphere or removing it before it enters the atmosphere.

As a general rule of thumb, organizations like the Intergovernmental Panel on Climate Change and the Rocky Mountain Institute recommend that to achieve the Paris target we need to be pursuing all three efforts simultaneously. Of course, any strategy we propose in pursuing them comes with trade-offs. The trick in reducing global carbon emissions will be to select a mix of strategies that will create the most equitable, economical, and environmentally sustainable pathway possible.

You will be exploring these concepts by creating your own “blueprint” for energy production and consumption from now until 2100. To do this you’ll need to 1) determine how to create sizable increases in global energy efficiency, 2) select a mix of energy resources to produce lower carbon emissions, and 3) select strategies for sequestering CO2.


Activity A – History of global energy consumption and production

Begin this activity by launching the interactive graph of global primary energy consumption from Our World in Data <https://ourworldindata.org/grapher/global-primary-energy>. Use this tool to determine the total energy consumed and the percentage of that energy provided by the sources listed in table 1 on the following page for selected years between 1800 and 2017. Record your results in Table 1.  Then use your results to answer the questions following the table.

image image
Figure 1a Figure 1b
Figure 1 – Global primary energy consumption in Terrawatt-hours between 1800 and 2017 (figure 1a) and percentage of total consumption provided by nine principal energy resources for that same period (figure 1b). You can access the graph in 1b by checking on the “Relative” box in the lower left corner of the graph shown in 1a. In both figures an information panel showing energy consumption or percent total consumption for selected years appears when you scroll over the graph.
A terawatt hour is a unit of energy equal to outputting 1 trillion watts for one hour. As a point of reference, this is the equivalent of the amount of energy consumed by one billion average toasters operating for an hour
Table 1 – Worksheet for recording results of Part A








Total energy


Percentage of total energy provided by the following fuels

Traditional biofuels


Crude Oil

Natural gas





Other renewables

Questions – Historical energy productions and consumption

  1. When did the “fossil fuel age” begin? Fossil fuels include coal, oil, and natural gas.
  2. When does nuclear appear in the energy mix?
  3. When does hydropower appear in the energy mix?
  4. When does wind, solar, and other renewables appear in the mix?
  5. How has the percentage of the total energy provided by each of these fuel groups changed since they first appeared?


Activity B: Global energypresent

Begin Part B by accessing the world energy flow chart produced by Lawrence Livermore National Laboratory’s Flow Charts project <https://flowcharts.llnl.gov/content/assests/images/charts/Energy/ENERGY_2011_World.png >.


Energy sources and consumption by sector
Figure 2 World Energy Flow – This diagram shows the major energy sources used to power global civilization and how that energy is used (consumption by sector) for 2011.
The two boxes on the right edge of the graph show how much of the energy consumed does useful work (energy services) vs. how much is simply released to the environment as heat (rejected energy). The lines connecting the various boxes represent energy flow between sources and consuming sectors.
The energy units in this graph are petajoules (PJ). One petajoule is 0.3 terawatt hours.

Questions – Present energy production and consumption

  1. What is the overall energy efficiency of global consumption? How do the four sectors on the right side of the diagram compare in terms of energy consumption and efficiency? The box non-energy is excluded from these sectors. Eenergy efficiency (SEE) is calculated this way               
               EE=Energy consumed by a sector that does useful work Total Energy consumed by that sector

   2. What percentage of the world’s total energy production is converted into electricity?

   3. What is the efficiency of the world’s electric power generation?

Part C – Global energy 2100

In Part C you will be designing a global energy mix for the year 2100 that will keep the increase in annual mean global temperature (MGT) in the year 2100 to less than 2.0°C. To do so you will be using the climate / energy simulator En-Roads.

To begin part C, launch EN-ROADS < https://en-roads.clim­­­­ateinteractive.org/scenario.html?v=2.7.6 >. Figure 3 shows what you should see after EN-ROADS has launched.

Figure 3 – The default screen for En-Roads.
The graph in upper left shows global primary energy sources projected from 2000 to 2100 in exajoules. An exajoule is 277.8 Terawatt hours. The graph on the right shows the increase in MGT given that energy mix and a variety of other factors. The sliders below the graphs are how you control those factors. These factors include energy supply, the efficiency and degree of electrification of sector consumption, global population and economic growth, land and industry emissions, and carbon sequestration strategies.


This default screen shows the “business as usual” (BAU) scenario. The BAU is what we might expect to see if stay on our current development pathway of increased energy use matched with increased use of fossil fuels. In this scenario the increase in MGT in 2100 is 4.1°C, nearly 2°C above the upper target of the 2015 Paris Accord. To reach the Paris target you will need to adjust some, or all of the factors controlled by the sliders in the bottom half of the screen. Here are the questions you will be addressing as you do so.

  1. Beginning with any of the existing energy sources (coal, oil, natural gas, bioenergy, renewables, and nuclear) what does it take to reduce or increase the amount of energy provided by that source? Watch the caption underneath each slide as you adjust that energy source.
  2. Given that in 2017 three fossil fuels provided nearly 85% of global energy consumption and produced 95% of all energy / industry related CO2 emissions, what would be the impact on the 2100 MGT increase of reducing all three fuels the maximum amount?
  3. Reducing which fuel has the greatest impact on the 2100 MGT increase? To do this reset the simulation and adjust each fuel separately, making sure to set it back to status quo before trying the next fuel.
  4. For the BAU scenario (reset the simulation) what impact does maximizing carbon price have on 2100 MGT increase? What is carbon price? Click on the three dots above the carbon price slider for an explanation?
  5. For the BAU scenario, what impact does setting population and economic growth to a minimum have on 2100 MGT increase? What impact does setting population and economic growth to a maximum have?
  6. What impact does setting all three fossil fuels to minimum, while increasing renewables to maximum have on 2100 MGT increase? Make sure to reset all sliders to status quo before doing this.
  7. What impact does setting all three fossil fuels to minimum, while increasing nuclear to maximum have on 2100 MGT increase? Make sure to reset renewables to status quo before maximizing nuclear.
  8. For the BAU scenario, what impact does setting electrification to maximum for transport, and buildings and industry have on 2100 MGT increase?
  9. For the BAU scenario, what impact does setting energy efficiency to maximum for transport, and buildings and industry impact 2100 MGT increase?
  10. For the BAU scenario, what is the 2100 MGT increase if land and industry emissions are reduced and carbon removal is increased the maximum amount?
  11. What is meant by deforestation, methane and other, afforestation, and technological carbon removal? Click on the three dots next to each title for an explanation.

Having done this background work, adjust energy supply, sector energy efficiency and electrification, land and industry emissions, and carbon removal, population, and economic growth to achieve the Paris target – 2100 MGT increase below 2.0°C with concerted effort to stay as close to 1.5°C as possible.

Record your results in Table 2 on the following page. Once this is done complete the graph in figure 4 to show your global energy plan from now until 2100. Finally, write a paragraph summary of your plan that outlines its major features and the tradeoffs inherent in the plan (strengths, limitations, risks, and benefits).

Table 2 – Worksheet for recording your results for the final problem in part C

2.1 Increase in MGT by 2100 ___________°C

2.2 Energy Supply

Energy produced by each source as read from the graph is in exajoules (EJ). Once you have recorded the contribution of each source, sum them to derive the total global consumption for each year.



% Total


% Total


% Total



Natural Gas



New Tech

Total Consumption


2.3 Carbon Price _________________________

2.4 Sector Consumption


Energy Efficiency



Buildings and Industry

2.5 Growth



2.6 Land and Industry Emission


Methane & Others

2.7 Carbon Removal




Figure 4 Global energy consumption and production from 1820 to 2100. Complete this figure by continuing the black line at the top of the stack out to 2100 based on each of total global consumption for 2020, 2060, and 2100. Then divide the space under the consumption curve at each of these years into segments based on the %total provided by each energy source.


Share This Book