This project is based on the International Energy Agency’s 2015 Energy Technology Perspectives (ETP) report, which constructed three alternative scenarios of fossil-fuel related annual carbon-dioxide emissions for the world from 2012 to 2050. The cumulative amount of greenhouse gases, specifically carbon dioxide, emitted into the atmosphere from today onward determines the increase in global temperature that will occur in the long-term (2100 and beyond) as a result of those emissions. In other words: More pollution means higher temperatures. However, it is not possible to know exactly how much the global average temperature will increase. For this reason, we presented temperature ranges, rather than specific degree marks.
Carbon dioxide (CO2) is the only greenhouse gas in the IEA’s scenarios, as it accounts for the largest amount of the greenhouse gases and solely determines the long-term temperature change due to its long lifetime in the atmosphere. Although there are other greenhouse gases, such as methane and nitrous oxide, focusing on only CO2 gives a good approximation of how various actions on emissions will affect overall long-term temperature.
The ETP scenarios, which IEA calls 6DS, 4DS, and 2DS, give cumulative CO2 emissions to 2050 that lead to different levels of global warming (temperature increases) by 2100. The scenarios track the fossil fuel related CO2 emissions of the Intergovernmental Panel on Climate Change’s RCP (“Representative Concentration Pathways”) scenarios that give 4 degrees, 3 degrees, and 2 degrees temperature changes by 2100, respectively. These RCP scenarios include post-2050 emissions and all sources of greenhouse gas emissions (including those from agriculture and land use change). On this basis, the IEA concludes that their 6DS, 4DS, and 2DS scenarios are consistent with being on an overall emissions pathway leading to a 50% likelihood of 4 degree, 3 degree and 2 degree temperature changes by 2100, respectively.
In our game, there are over 30,000 possible combinations of answers to the eight questions. The starting combination (before you pick your own set of answers) gives cumulative emissions to 2050 that equal those of the 6DS scenario leading to a likely temperature change of 4 degrees Celsius by 2100. For combinations of answers that give cumulative emissions greater than the 6DS cumulative emissions, the temperature change indicator will show greater than 4 degrees Celsius. For combinations of answers that give cumulative emissions that fall between those for the 6DS and 4DS scenarios, the indicator will show 3 to 4 degrees. Similarly, if the cumulative emissions fall between 4DS and 2DS cumulative emissions, the indicator reads 2 to 3 degrees. For cumulative emissions less than 2DS emissions the indicator shows <2°C.
Adam Schlosser, from the Massachusetts Institute of Technology, and Fabian Wagner, from the International Institute for Applied Systems Analysis, in Vienna, helped develop and review the methodology used for the Two° online challenge.