Whole Atmosphere Climate Change: Dependence on Solar Activity

Solomon, Stanley C.; Liu, Hanli; Marsh, Daniel R.; McInerney, Joseph; Qian, Liying; Vitt, Francis

doi:10.1029/2019ja026678

Cited by 43 publications

(80 citation statements)

References 55 publications

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“…This can therefore also push global mean trends to be more negative than they would be due to the increase in CO 2 concentration alone. This is true for the neutral temperature at 400 km as well and may help to explain why the trends in especially the neutral temperature and h m F 2 we found remained somewhat large compared to Solomon et al (2018, 2019) even after solar cycle influences were removed as much as possible.…”

Section: Discussionsupporting

confidence: 72%

“…field. This is the other key difference between our study and Solomon et al (2018and Solomon et al ( , 2019, who kept the Earth's magnetic field fixed. Since magnetic field changes and their effects on the upper atmosphere are location-dependent, it is appropriate to go beyond global mean quantities for this and examine the spatial variations in trends.…”

Section: Global Mean Trendsmentioning

confidence: 87%

“…Solomon et al (2018, 2019) performed controlled experiments with WACCM‐X to determine the magnitude of anthropogenic climate change throughout the atmosphere, comparing the intervals 1972–1976 and 2001–2005 with each other. Solar and geomagnetic activity levels were kept fixed in their simulations, which examined solar minimum and solar maximum background conditions separately.…”

Section: Global Mean Trendsmentioning

confidence: 99%

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Analysis and Attribution of Climate Change in the Upper Atmosphere From 1950 to 2015 Simulated by WACCM‐X

Cnossen

2020

JGR Space Physics

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Monitoring climatic changes in the thermosphere and ionosphere and understanding their causes is important for practical purposes. To support this effort and facilitate comparisons between observations and model results, a long transient simulation with the Whole Atmosphere Community Climate Model eXtension (WACCM-X) from 1950 to 2015 was conducted. This simulation used realistic variations in solar and geomagnetic activity, main magnetic field changes, and trace gas emissions, including CO 2 , thereby including all known drivers of upper atmosphere climate change. Analysis of the full 1950-2015 interval with a standard multilinear regression approach demonstrated difficulties in removing solar cycle effects sufficiently to obtain reliable trends. Results improved when an (F10.7a) 2 was included in the regression model, in addition to terms for F10.7a, K P , and the trend itself. Comparisons with previous studies and analysis of spatial variations in trend estimates confirmed that the increase in CO 2 concentration is the main driver of trends in thermosphere temperature and density, but at high (magnetic) latitudes effects of main magnetic field changes play a role as well, especially in the Northern Hemisphere. Spatial patterns of trends in h m F 2 , N m F 2 , and total electron content indicate a superposition of CO 2 and geomagnetic field effects, with the latter dominating trends in the region of ∼50-20 • N, ∼60 • W to 20 • E. Additional model experiments to investigate the indirect dynamical effects of climate change in the lower atmosphere (<50 km) on the upper atmosphere (>100 km) suggested that these effects are small and insignificant. However, current model limitations could mean that these effects are underestimated. Plain Language Summary A simulation with a state-of-the-art global model of the atmosphere from the surface up to about 500-km altitude was done for the period 1950-2015 to study climate change in the upper atmosphere (above 100-km altitude). The simulation included realistic variations in solar and geomagnetic activity, the Earth's magnetic field, and trace gas emissions, including CO 2. Solar and geomagnetic activity variations occur naturally as part of the ∼11-year solar cycle and have a large effect on the upper atmosphere. Still, by removing these effects as much as possible, we showed that the increase in CO 2 concentration is the main cause of cooling in the upper atmosphere, while effects of magnetic field changes also play a role near the poles, especially in the Northern Hemisphere. Long-term trends in the charged portion of the upper atmosphere, the ionosphere, are caused by both CO 2 and magnetic field effects, with the latter being most important in the region of ∼50 • S to 20 • N, ∼60 • W to 20 • E. Additional model experiments to investigate effects of climate change in the lower atmosphere (<50 km) on the upper atmosphere suggested that these are small. However, they might be underestimated by the model.

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Section: Discussionsupporting

confidence: 72%

Section: Global Mean Trendsmentioning

confidence: 87%

Section: Global Mean Trendsmentioning

confidence: 99%

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Analysis and Attribution of Climate Change in the Upper Atmosphere From 1950 to 2015 Simulated by WACCM‐X

Cnossen

2020

JGR Space Physics

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“…Recent modeling studies by Solomon et al (2018) and Solomon et al (2019) found that the increase in CO 2 concentration between the 1972-1976 and 2001-2005 periods caused a decrease in global mean N m F 2 of 1.2% per decade. Changes in global mean TEC would probably be somewhat smaller than this, as the F 2 peak is the part of the ionosphere that shows the largest response to CO 2 changes.…”

Section: Discussionmentioning

confidence: 99%

Simulated Trends in Ionosphere‐Thermosphere Climate Due to Predicted Main Magnetic Field Changes From 2015 to 2065

Cnossen

Maute

2020

JGR Space Physics

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The strength and structure of the Earth's magnetic field is gradually changing. During the next 50 years the dipole moment is predicted to decrease by ∼3.5%, with the South Atlantic Anomaly expanding, deepening, and continuing to move westward, while the magnetic dip poles move northwestward. We used simulations with the Thermosphere-Ionosphere-Electrodynamics General Circulation Model to study how predicted changes in the magnetic field will affect the climate of the thermosphere-ionosphere system from 2015 to 2065. The global mean neutral density in the thermosphere is expected to increase slightly, by up to 1% on average or up to 2% during geomagnetically disturbed conditions (K p ≥ 4). This is due to an increase in Joule heating power, mainly in the Southern Hemisphere. Global mean changes in total electron content (TEC) range from −3% to +4%, depending on season and UT. However, regional changes can be much larger, up to about ±35% in the region of ∼45 • S to 45 • N and 110 • W to 0 • W during daytime. Changes in the vertical ⃗ E × ⃗ B drift are the most important driver of changes in TEC, although other plasma transport processes also play a role. A reduction in the low-latitude upward ⃗ E × ⃗ B drift weakens the equatorial ionization anomaly in the longitude sector of ∼105-60 • W, manifesting itself as a local increase in electron density over Jicamarca (12.0 • S, 76.9 • W). The predicted increase in neutral density associated with main magnetic field changes is very small compared to observed trends and other trend drivers, but the predicted changes in TEC could make a significant contribution to observationally detectable trends.

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“…However, the actual observation of climate change contains both effects in several different time scales. Modeling efforts have been made to separate these two mechanisms (e.g., Egorova et al 2018;Solomon et al 2019). Comparison of these modeling efforts with longterm observation becomes increasingly important to identify the mechanisms on solar forcing to climate change.…”

Section: Separation Of Anthropogenic Effect and Solar Variability Effectmentioning

confidence: 99%

A review of the SCOSTEP’s 5-year scientific program VarSITI—Variability of the Sun and Its Terrestrial Impact

Shiokawa

Georgieva

2021

Prog Earth Planet Sci

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The Sun is a variable active-dynamo star, emitting radiation in all wavelengths and solar-wind plasma to the interplanetary space. The Earth is immersed in this radiation and solar wind, showing various responses in geospace and atmosphere. This Sun–Earth connection variates in time scales from milli-seconds to millennia and beyond. The solar activity, which has a ~11-year periodicity, is gradually declining in recent three solar cycles, suggesting a possibility of a grand minimum in near future. VarSITI—variability of the Sun and its terrestrial impact—was the 5-year program of the scientific committee on solar-terrestrial physics (SCOSTEP) in 2014–2018, focusing on this variability of the Sun and its consequences on the Earth. This paper reviews some background of SCOSTEP and its past programs, achievements of the 5-year VarSITI program, and remaining outstanding questions after VarSITI.

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Whole Atmosphere Climate Change: Dependence on Solar Activity

Cited by 43 publications

References 55 publications

Analysis and Attribution of Climate Change in the Upper Atmosphere From 1950 to 2015 Simulated by WACCM‐X

Analysis and Attribution of Climate Change in the Upper Atmosphere From 1950 to 2015 Simulated by WACCM‐X

Simulated Trends in Ionosphere‐Thermosphere Climate Due to Predicted Main Magnetic Field Changes From 2015 to 2065

A review of the SCOSTEP’s 5-year scientific program VarSITI—Variability of the Sun and Its Terrestrial Impact

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