Climate Changes in the Upper Atmosphere: Contributions by the Changing Greenhouse Gas Concentrations and Earth's Magnetic Field From the 1960s to 2010s

Abstract

Greenhouse gases (GHGs) in the Earth's atmosphere, including CO 2 , CH 4 , H 2 O, and O 3 , absorb as well as emit infrared radiation. At lower altitudes where the air is dense, they are optically thick to outgoing infrared radiation and thus produce a heating effect. In contrast, at higher altitudes where the air is increasingly tenuous, they become optically thin to outgoing infrared radiation and therefore, produce a cooling effect. Note that the main role of O 3 in the atmosphere is as a solar ultraviolet (UV) absorber in the stratosphere. Therefore, the stratospheric temperature response (and consequently the density response at higher altitudes) to O 3 increases is opposite to that of the other three major GHGs. The stratospheric O 3 trend is not monotonic (Figure 1), and until recently was negative, thus contributing to cooling like the other three GHGs, but for a different reason. Observational and modeling studies found that since the 1960s, the long-term changes of these GHGs have caused warming in the troposphere (∼0.

Long‐Term Trends in the Upper Atmosphere Using the Incoherent Scatter Radar Observations Over Arecibo

“…Over Millstone Hill above the altitude of 220 km, cooling trends are stronger in ISR measurements than in the WACCM-X model. These discrepancies between the WACCM-X model and ISR data sets were also reported by Qian et al (2021).…”

“…The increasing concentration of anthropogenic greenhouse gases (GHGs) leads to global warming in the lower atmosphere but can cool the upper atmosphere (Laštovička, 2015, 2021; Laštovička et al., 2006; Roble & Dickinson, 1989). However, the observed upper atmospheric cooling could also be caused by long‐term changes in geomagnetic activity (Liu et al., 2021; Mikhailov, 2006), secular changes in the Earth's magnetic field (Cnossen, 2014, 2020a; Qian et al., 2021; Yue et al., 2018), increased gravity wave activity (Oliver et al., 2013), and also other drivers which are in debate (Laštovička, 2015; Oliver et al., 2014, 2015, 2013).…”

A Realistic Projection of Climate Change in the Upper Atmosphere Into the 21st Century

“…These auroral changes in TEC are therefore also likely to be driven primarily by changes in the Earth’s magnetic field. However, in other parts of the world, the increase in CO 2 concentration probably plays a more important role, causing a negative trend in peak electron density and TEC (e.g., Qian et al., 2021).…”

“…The increase in atmospheric CO 2 concentration is thought to be the main driver of the global mean cooling and contraction of the upper atmosphere (e.g., Laštovička et al., 2006), with other trace gases playing a relatively minor role (Qian et al., 2013). The secular variation in the Earth's magnetic field also drives significant long‐term trends in the upper atmosphere, in particular in the ionosphere, although these vary strongly with location and largely cancel out in a global average (Cnossen, 2014, 2020; Qian et al., 2021).…”

Long-term variations and residual trends in the E, F and sporadic E (Es) layer over Juliusruh, Europe

“…are of natural origin. However, lately using whole atmosphere model simulations Qian et al (2021) found that trends in the thermosphere were predominantly driven by greenhouse gases, whereas in the foF2, hmF2 and Te the role of greenhouse gases and of the secular change of the geomagnetic field were comparable in some regions. However, globally the role of magnetic field change is negligible because locally it is both positive and negative.…”