On April 22, 2020, Bloomberg News published an interactive exploring the impact of different climate solutions using Climate Interactive’s En-ROADS simulator. Below you will find detailed explanations and technical notes of the settings used in the article and the model dynamics at play.
The En-ROADS Climate Solutions Simulator is a fast, powerful climate simulation tool for understanding how we can achieve our climate goals through changes in energy, land use, consumption, agriculture, and other policies. The simulator focuses on how changes in global GDP, energy efficiency, technological innovation, and carbon price influence carbon emissions, global temperature, and other factors. It is designed to provide a synthesis of the best available science on climate solutions and put it at the fingertips of groups in policy workshops and roleplaying games. These experiences enable people to explore the long-term climate impacts of global policy and investment decisions. Led by the team at Climate Interactive, En-ROADS has benefited from a close collaboration between Climate Interactive, Tom Fiddaman of Ventana Systems, Prof. John Sterman of MIT Sloan, and Prof. Juliette Rooney-Varga of UMass Lowell’s Climate Change Initiative.
For additional information, please explore these resources:
- The En-ROADS User Guide for background on the dynamics of En-ROADS, tips for using the simulator, general descriptions, real-world examples, slider settings, and model structure notes for the different sliders in En-ROADS.
- The En-ROADS Reference Guide for extensive model details, including data sources, model assumptions, dynamics, and structure.
- Our Confidence Building Webinar to understand how confidence in the model was built.
- This page to learn more about the Business as Usual scenario used in En-ROADS.
No Silver Bullets
In this section, the Bloomberg article explores five well-known climate solutions and demonstrates their individual impact on net greenhouse gas emissions by 2100 using En-ROADS.
The scenario tested in the article moves the growth in the percentage of final transportation energy that comes from electricity from its Business as Usual (BAU) path to a “highly incentivized,” fast growth scenario that increases the growth by 4% per year, leading it to reach 65% by 2080 (up from 16% in 2080 originally).
Note that the amount of transportation that becomes electric is limited by the broad definition of transportation energy in En-ROADS – it encompasses areas that are less conducive to electricity use such as shipping and air travel.
To understand why the system delivers the modest results in emissions reduction in this scenario, consider that much of the extra electricity generation sparked by the increase in electrified transport comes from the existing electric energy mix which is dominated by coal, leading the amount of energy that comes from that high-density energy source to go up, even as the amount of energy from oil goes down. Absent other policy support for growth in renewable energy or other zero carbon energy sources, the increased demand for electricity doesn’t drive use of low emissions energy supply like wind and solar.
Overall, the world burns less oil but more coal and, on net, warming is reduced modestly but less than many would hope, prompting a push to explore policies that decarbonize the grid in tandem with boosts to electric transport.
The scenario tested in the article moves the growth in nuclear primary energy demand from its BAU path of steadily increasing through the end of the century, to a ‘highly subsidized’ scenario of $0.07/kWh where we see a sharp and continued increase in nuclear demand beginning in 2030.
In this scenario, primary energy demand from nuclear reaches 76 EJ/year in 2050 and 295 EJ/year by the end of the century. To compare to the projections for the SSP2 2.6 scenarios for the six Integrated Assessment Models (IAMs), the 2050 values are 112 for PBL IMAGE, 130 for IIASA MESSAGE-GLOBIOM, 74 for NIES AIM/CGE, 269 for PNNL GCAM4, 130 for PIK REMIND-MAGPIE, and 103 for EIEE WITCH-GLOBIOM.
Nuclear capacity grows steadily to accommodate the increased demand, and by 2050 reaches 2,795 GW. The International Atomic Energy Agency (IAEA) projects a much lower 715 GW by 2050 in their high case scenario.
With nuclear energy highly subsidized, the demand for coal and natural gas decreases as nuclear becomes less expensive. The demand for oil decreases only slightly since nuclear energy cannot replace many of the non-electric uses fulfilled by oil, namely fuel engines in vehicles.
While a nuclear subsidy drives demand for fossil fuels down, it is important to note that it also competes with the demand for renewables (wind, solar, hydro, and geothermal). A decrease in renewable energy negatively impacts temperature change and counteracts some of the climate benefit from subsidized nuclear energy. Another dynamic at play is the ‘rebound effect,’ where the subsidy leads to a decrease in the cost of energy which leads to an increase in energy consumption.
The scenario tested in the article moves the growth in renewable primary energy demand from its BAU path of steadily increasing through the end of the century, to a ‘highly subsidized’ scenario of $0.07/kWh where we see sharp exponential growth in demand beginning in 2030 and continued linear increase from around 2050 through the end of the century. In En-ROADS, the Renewables slider includes hydro, wind, solar, and geothermal power.
In this scenario, energy production from Renewables reaches 208 EJ/year by 2050 and 448 EJ/year by the end of the century. This is above the projections for the SSP2 2.6 scenarios for the six Integrated Assessment Models (IAMs). Under these projections for 2050, the EJ/year of renewable energy production is around 65 for PBL IMAGE, 118 for IIASA MESSAGE-GLOBIOM, 114 for NIES AIM/CGE, 77 for PNNL GCAM4, 146 for PIK REMIND-MAGPIE, and 161 for EIEE WITCH-GLOBIOM. Some additional projections, such as Shell’s Sky scenario, estimate a higher value than that in En-ROADS, of about 264 EJ/year in 2050.
Much of the dynamics at play are similar to what we saw when highly subsidizing nuclear energy, in that fossil fuels are displaced, nuclear and renewables compete with each other, and there is a rebound effect. With renewable energy highly subsidized, the demand for coal and natural gas decrease as renewables become an attractive alternative. The demand for oil decreases only slightly since renewable energy cannot replace many of the non-electric uses fulfilled by oil, namely fuel engines in vehicles.
While a renewable subsidy drives demand for fossil fuels down, it is important to note that it also competes slightly with the demand for nuclear energy. The rebound effect is also noticeable here, where the subsidy leads to a decrease in the cost of energy which leads to an increase in overall energy consumption.
Direct Air Capture
The scenario tested in the article explores the impact of Direct Air Capture (DAC) being deployed in the year 2020 and achieving its maximum potential by 2100. This max capacity is based on The Royal Society’s Greenhouse gas removal report, that outlines the range of DAC’s global carbon dioxide removal potential to be 0.5-5 Gigatons CO2/year. We used the middle of the range to set the max potential in En-ROADS for DAC to be 2.8 GigatonsCO2/year by the end of the century. To adjust this maximum in En-ROADS, go to Simulation > Assumptions > Carbon dioxide removal maximum.
To understand the seemingly modest impact of a large DAC effort, it is important to compare this removal effort with the total amount of CO2 being emitted. With no action on emissions reductions, CO2 emissions alone reach 86 Gigatons/year, with the DAC effort removing 2.8. In this case, CO2 concentration levels continue to steadily increase through the end of the century.
The scenario tested in the article moves the growth in global afforestation efforts from its BAU path of zero to “high growth,” or 100% of available land for afforestation being utilized. This high growth scenario results in 6.4 Gigatons CO2 removed annually from afforestation by 2100.
Note that the simulation allocates 10 years to secure land for afforestation and 30 years to plant new trees around the world. These settings can be adjusted in the Advanced View of the Afforestation slider. Additional assumptions, such as afforestation growth time (set to 80 years), max available land for afforestation (set to 700 Mha), max carbon density on afforested land (set to 0.6 Gigatons C/Mha), and percent loss per year of afforestation (set to 2%/year) can be adjusted under Simulation > Assumptions > Afforestation settings.
These delays in implementation and time required for mature growth alongside the amount of land required to fulfill these afforestation efforts provide insight into the modest impact in emissions reductions form afforestation efforts. In particular, note the time it takes for removals to reach their peak – after 2080.
Viewing the sources of greenhouse gas emissions provides additional insight into the small fraction of emissions comprised by land use (notice the area of removals below the “zero” line relative to the emissions above it). Overall, land use emissions do become net negative, but absent other actions, emissions from Energy CO2 (and to a lesser extent Methane, Nitrous Oxide, and the F-gases) continue to be the major source of greenhouse gas emissions.
Other analysis with En-ROADS of afforestation (e.g, a video and a blog post) supplements this above and notes the importance of planting trees and also setting modest expectations about the positive impact on climate change.
The scenario tested in the article explores a $75/ton CO2 carbon price, achieved by ramping it up over ten years.
Demand for coal decreases significantly, as it is hardest hit by the carbon price due to its high carbon density. To reduce their carbon emissions, coal producers deploy increased Carbon Capture and Storage (CCS) technology. As demand for all other carbon emitting energy sources (oil, natural gas, and bioenergy) decreases as well, we see an increase in demand for low carbon energy sources such as renewables and nuclear.
Important factors to consider when examining a carbon price are some of the financial outcomes. With the proposed carbon price, we see an increase in cost of energy. The $75/ton price yields a revenue of approximately 4.3 trillion $/year by the end of the century.
Play the Game
In this final section, users can select from a combination of 10 different climate solutions to test in En-ROADS. Selecting all solutions limits temperature increase to 2 degrees by 2100.
The settings for each solution used in the 2 degree scenario are as follows:
Build renewable power
Renewable energy (from wind, solar, hydro, and geothermal power) is ‘subsidized’ at $0.03/kWh.
Enact a carbon price
A ‘high’ carbon price of $75/ton of CO2 is implemented.
Make transportation more energy efficient
Energy efficiency of the transport sector is ‘increased’ to 1%/year energy intensity improvement.
The electrification of the transport sector is ‘highly incentivized’ to mandate that 4% of new transport per year be powered by electricity rather than fuels.
Make buildings and industry more energy efficient
Energy efficiency of buildings and industry is ‘highly increased’ to 3.7%/year energy intensity improvement.
Electrify buildings and industry
The electrification of buildings and industry is ‘incentivized’ to mandate that 2.7% of new building construction, industry, and appliances be powered by electricity rather than fuels.
Deforestation is ‘highly reduced’ to a reduction in land use & forestry emissions of 8%/year.
Cut methane and other pollution from agriculture and industry
Emissions from Methane & other GHGs are ‘moderately reduced’ by 50%.
There is ‘high growth’ in afforestation efforts, with 70% of land available for afforestation being utilized.
Mass-produce CO2 removal technologies
Technological Carbon Removal (includes Bioenergy Carbon Capture & Storage (BECCS), Direct Air Capture, Enhanced Mineralization, Agricultural Soil Carbon Sequestration, and Biochar) sees ‘medium growth’ of 50% effort out of 100% maximum potential, with that potential defined as the mid-point of the estimates in the The Royal Society’s 2018 Greenhouse gas removal report.