Long‐term temperature trends in the middle and upper atmosphere

Abstract

We analyse data from weekly rocket temperature soundings up to 75 km carried out since mid‐1960s at polar (Heiss Island, 80.6°N and Molodezhnaya, 67.7°S), temperate (Volgograd, 48.7°N and Balkhash, 46.8°N) and tropical (Thumba, 8.5°N) latitudes. All records show significant cooling which is of the order of a few degrees K at 30–40 km, 10 K at 50 km and 20 K at 60–70 km. In the mesosphere the temperature trends are estimated from the hydroxyl rotational temperature records which start in 1957 at Zvenigorod (55.7°N) and Abastumani (41.8°N). These are related to the mesopause at 87 km and also show a cooling of about 30 K during the time. The cooling is qualitatively consistent with increasing concentration of greenhouse gases but may also reflect the changing chemistry of stratosphere and mesosphere, which is clearly seen in increasing emission intensities of hydroxyl during the last decades. Therefore the stratosphere and mesosphere may be regions with the strongest signals of global change.