A simple way to think about the structure of En-ROADS is by considering the drivers of climate impacts. In the simulator, the concentration of greenhouse gases drives up global temperature, which leads to various impacts (e.g., sea level rise and ocean acidification).
The concentration of greenhouse gases in the atmosphere is driven by four main sources:
- Energy CO2 Emissions from burning coal, oil, gas, and biomass. CO2 emissions from energy currently comprise about 65% of greenhouse gas emissions.
- Land Use CO2 Emissions such as forestry and land use change. CO2 emissions from land use currently comprise about 7% of greenhouse gas emissions.
- Carbon Dioxide Removal approaches that pull carbon dioxide out of the atmosphere and store it in plants, soils, or underground leading to a decrease in CO2 concentrations.
- Other Greenhouse Gas Emissions such as methane, N2O, and F-gases. Non-CO2 emissions currently comprise about 28% of total greenhouse gas emissions.
Going further, CO2 emissions from energy are driven by four factors, which is known as the “Kaya Identity”. Population, consumption (GDP/capita), energy intensity (energy use per dollar of GDP), and carbon intensity (CO2 emissions per unit of energy) are all multiplied together and the result is overall energy CO2 emissions. In this way, at a high level, reducing CO2 emissions is about four things: fewer people, less consumption, more efficiency, and less high-carbon energy supplies.