A realistic projection of climate change in the upper atmosphere into the 21st century

Climate change in the upper atmosphere (∼90 − 500 km altitude) has important impacts on practical applications. To prepare for these, realistic projections of future climate change are needed. The first climate projection up to 500 km altitude is presented here based on a long transient simulation with the Whole Atmosphere Community Climate Model eXtension, following Shared Socio-economic Pathway 2-4.5, a moderate emission scenario. Effects of predicted main magnetic field changes and reasonable solar radiative and particle forcings are also included. The predicted global mean cooling in the thermosphere and associated decline in thermosphere density for 2015-2070 are significantly stronger than for the historical period, which is ascribed to the more rapid increase in CO2 concentration. Trends in global mean ionospheric parameters also increase in magnitude, but there are considerable spatial variations, caused by changes in the Earth’s magnetic field. The largest ionospheric changes are expected in the region of ∼50°S-20°N, ∼90-0°W