Fall (SON) average temperatures in the Greater Yellowstone Area are projected to warm by 4.3° to 4.9°F (2.3 to 2.7°C) by the middle of the 21st century (2030-2059). This projection is the average of 10 global climate models using the IPCC’s A1B emissions scenario. A1B is the middle-level scenario for both carbon dioxide emissions and economic growth, with atmospheric concentrations of CO2 rising from 390 ppmv at present to 550 ppvm by mid-century.