This paper briefly reviews long-term trends in the mesosphere, thermosphere and ionosphere as a part of global climate change. Anthropogenic emissions cause cooling in the upper atmosphere due to optical thinning of CO_2 layer. CO_2 is the dominant trend driver but anthropogenic changes of stratospheric ozone, long-term changes of geomagnetic and solar activity, atmospheric wave activity and water vapour content, and secular change of the Earth’s magnetic field also play a role. This makes the pattern of trends spatially as well as temporally unstable. A consistent, although incomplete, scenario of trends in the upper atmosphere and ionosphere is presented. More realistic height profiles of CO2 helped to reduce substantially (or even remove) the quantitative difference between observational and modelled trends. Decreasing thermospheric density causes the lifetime of orbiting space debris to increase, which is becoming a significant threat to important satellite technologies.
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