The upper atmosphere is cooling as it compensates for the heating of the surface caused by the increased energy in the climate cycle due to human activity increasing Greenhouse Gases.
http://science.sciencemag.org/content/311/5764/1138
https://journals.ametsoc.org/doi/abs/10.1175/1520-0442(2002)015<1659:IADVOP>2.0.CO;2
