Summer (JJA) average temperatures in the Greater Yellowstone Area are projected to warm by 4.7° to 5.4°F (2.6 to 3.0°C) by the middle of the 21st century (2030-2059). Summer average temperatures are projected to warm more than other seasons. 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.