Upper Atmosphere Responses to IPCC's Worst Scenario of CO2 Increase in the 21st Century
Han Ma1,2, Huixin Liu, Hanli Liu3, Libo Liu4 (2025) (link to paper)
1Key Laboratory of Planetary Science and Frontier Technology, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
2Heilongjiang Mohe Observatory of Geophysics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
3High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO, USA
4College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
(Figure 2) The latitude‐height distribution of parameters in 2008 (the top panels) and their responses to tripled CO2 emission (the bottom panels) in June. These normalized data are a series of zonal mean value at fixed altitude and latitude. (a1, a2): atmospheric temperature (T) and its response (∆T); (b1, b2): neutral mass density (ρ) and its response (∆ρ); (c1, c2): electron density (Ne) and its response (∆Ne). The symbol “∆” represents the difference of normalized data: Y (2088)‐Y (2008).
This study uses a sophisticated climate model (CESM2/WACCM-X) to predict how Earth's upper atmosphere (100–500 km altitude) will respond to a worst-case CO₂ increase scenario by 2090, where concentrations nearly triple from ~350 ppm to ~1,000 ppm. The simulations reveal three primary effects:
First, thermospheric temperature, neutral density, and electron density decrease overall due to CO₂'s cooling effect, with electron density showing a transition from increase to decrease above ~220 km altitude. Second, the north-south (meridional) wind circulation accelerates by 5–10 m/s, especially during June, indicating a faster global wind pattern. Third, atmospheric tides—24-hour cycles weaken above 200 km but strengthen below it, while 12-hour cycles weaken throughout the thermosphere. These dynamical changes align with predictions from another model (GAIA), confirming that CO₂-induced cooling accelerates upper-atmospheric circulation. The findings help anticipate impacts on satellites, navigation systems, and space weather.
Impact of Increasing Greenhouse Gases on the Ionosphere and Thermosphere Response to a May 2024‐Like Geomagnetic Superstorm
Nicholas M. Pedatella1,2, Huixin Liu, Hanli Liu1, Adam Herrington3, Joseph McInerney1 (2025) (link to paper)
1High Altitude Observatory, NSF National Center for Atmospheric Research, Boulder, CO, USA
2COSMIC Program Office, University Center for Atmospheric Research, Boulder, CO, USA
3Climate and Global Dynamics Laboratory, NSF National Center for Atmospheric Research, Boulder, CO, USA
(Figure 4) Storm‐time change in total electron content (ΔTEC) in (a) 2016, (b) 2040, (c) 2061, and (d) 2084. The ΔTEC is calculated as the difference between the TEC on May 11 and the average TEC on May 8–9. Difference in the magnitude of the storm‐time change from the 2016 baseline in (e) 2040, (f) 2061, and (g) 2084. (h–n) Same as (a–g) except the results are for the relative storm‐time change in TEC.
Using the Community Earth System Model with thermosphere-ionosphere extension (CESM WACCM-X), this study investigates how increasing greenhouse gas concentrations affect the ionosphere and thermosphere's response to geomagnetic storms. The May 2024 geomagnetic superstorm is simulated under four different CO2 scenarios, ranging from present-day levels (403 ppmv) to nearly doubled concentrations (918 ppmv) projected for 2084. The results show that higher CO2 concentrations significantly weaken the absolute response of both the ionosphere and thermosphere to geomagnetic storms. Specifically, the thermosphere neutral density response decreases by 20-25% and the ionospheric response weakens by up to 50% as CO2 levels increase from current to future projected levels. However, when expressed as relative changes compared to background conditions, the storm responses actually strengthen with higher CO2 concentrations, primarily because the background neutral densities become much smaller in a high-CO2 atmosphere. The weakening absolute response occurs due to reduced Joule heating at higher altitudes, which is the primary energy source driving storm-time changes in the upper atmosphere. This study provides the first comprehensive assessment of how climate change may alter space weather impacts on Earth's upper atmosphere.
This paper has received much attention from the public. Here are links from CNN, Astronomy, and NCAR.
https://www.astronomy.com/science/satellites-face-new-challenges-from-solar-storms/
https://edition.cnn.com/2025/08/14/climate/solar-storms-satellites-global-warming
https://news.ucar.edu/133035/atmosphere-changes-so-will-its-response-geomagnetic-storms
https://www.kyushu-u.ac.jp/f/63050/2508_Huixin_climate_change_geomagnetic_storms_UCAR_new.pdf
Sporadic-E layer responses to super geomagnetic storm 10-12 May 2024
Lihui Qiu, Huixin Liu (2025) (link to paper)
(Figure 1) Geographical distribution of the (a) daily averaged Es layer intensity derived from S4 data, (b) daily averaged Es layer intensity derived from S4 data on 11 May, (c) Es layer perturbation on 11 May. (d-f) is the same as Figure a-c, but for SNR data. The magnetic equator is indicated as a red dashed curve.
Using 37 ground-based ionosondes distributed globally and space-based COSMIC-2 radio occultation observations, this study investigates the responses of Es layers to the May 2024 super geomagnetic storm. The results show that Es layers were significantly enhanced during the recovery phase of geomagnetic storm. In addition, the enhanced Es layers mainly occurred over Southeast Asia, Australia, the South Pacific and the East Pacific. The temporal evolution of foEs disturbances over the Asian-Australian sector clearly shows the “wave propagation” characteristics from high to low latitudes, indicating that the enhancements of the Es layers are most likely caused by the disturbed neutral winds in the E region. This study presents observational evidence for the downward impacts of the geomagnetic storm on the E-region ionosphere.
Generation Of Quasi-periodic Dayside Medium Scale Traveling Ionospheric Disturbances (MSTIDs) By Intermittent Lobe Reconnection
Yating Xiong1 , Huixin Liu, Run Shi1 , Zanyang Xing2 , Sheng Lu2 , Qiang Zhang1 , Zhiwei Wang1 , Desheng Han1 (2025) (link to paper)
1State Key Laboratory of Marine Geology, School of Ocean and Earth Science, Tongji University, Shanghai, China
2Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Sciences, Shandong University, China
(Figure) (a-b) Polar projections of the fields of view (FOVs) of Hankasalmi radar and EISCAT Svalbard radar at 09:00 and 13:00 UT on 14 December 2012. The blue fan-shaped area represents the FOV of Hankasalmi radar beam 7. The green straight line shows the FOV of the EISCAT Svalbard radar Longyearbyen 32M, and the red five-pointed star marks the position of the EISCAT Svalbard radar. (c) Variations of the interplanetary magnetic field components BX(blue), BY (red), and BZ (black) between 08:00 and 13:00 UT. (d, e) The range-time plot of velocity and power (negative away, poleward from radar) observed by beam 7 of Hankasalmi radar in channel A on the same day.
The Medium-Scale Traveling Ionospheric Disturbances (MSTIDs) can be excited by many sources. Among those magnetic reconnections has been proposed as a potential driver for dayside MSTIDs, but direct evidence has been limited. Using ground-based radar data from the Super Dual Auroral Radar Network on December 14, 2012, we observed quasi-periodic multiple MSTIDs propagating from auroral latitudes to mid latitudes near magnetic local noon, which showed one-to-one correspondences to intermittent lobe reconnections with periodicities of about 20–30 minutes. Simultaneous EISCAT Svalbard incoherent scatter radar data revealed enhanced electric field and Joule heating within the cusp region following each lobe reconnection. These multi-instrument observations strongly suggest lobe reconnection as a possible driver for the dayside MSTID.
Modelling of three-dimensional structure and dynamics of the large-scale sporadic E layers over East Asia
Lihui Qiu, Huixin Liu (2025) (link to paper)
(Figure 1) An example of the 2-D slices of Fe+ density derived from the Es layer model, i.e., (a) horizontal slices, (c) longitudinal slices, and (d) latitudinal slices. (b) Same as Figure 3a, but at an altitude range of 100-125 km in order to show more details.
Using the Fe+ layer as a proxy for Es layer, in this study, we investigated the structural and dynamic characteristics of the large-scale Es layers extending thousands of kilometers over East Asia by using a 3-D Es layer numerical model driven by neutral winds from the Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension model (WACCM-X). The simulation results show that the Es layer is a tilted blanket rather than a narrow flat band. In addition, the Es layers mainly occur in the 3-D spatial position of the convergent vertical wind shear. The apparent horizontal velocity (~300-400 m/s) of Es structure is mostly westward and northward, which is different from the ion drift velocity (~100 m/s). This indicates that Es structure can develop rapidly over a large area simultaneously rather than drifting from one location to the next. COSMIC targets the locations of Es layers with all intensities that including much smaller intensity at a given time from a global perspective. The migration speed of hotspot of Es layer occurrence recorded by COSMIC satellites matches the apparent velocity. The GNSS receivers track the dense ion clusters (foEs > 14 MHz) to measure the drift direction and speed of extremely strong Es layer, which matches the ion drift velocity.
Wave Spectral Changes in the Thermosphere and Ionosphere Related to the PEDE 2018 Dust Event on Mars Observed by MAVEN NGIMS
Noritsugu Nagata, Huixin Liu, Hiromu Nakagawa* (2025) (link to paper)
*Graduate School of Science, Tohoku University, Sendai, Japan
(Figure 5) The occurrence rate of apparent wavelengths for each species obtained during two periods : the low-dust period (upper) and the global dust period (lower), where altitudes between 165 and 205 km, X-bin is on a log scale
In 2018, Mars experienced a Planet Encircling Dust Event (PEDE-2018), which had significant impacts on the atmosphere. In this study, we examined changes in wave signatures (amplitudes and apparent wavelengths) associated with PEDE-2018. In-situ density measurements from the NGIMS (Neutral and Ion Gass Mass Spectrometer) instrument on MAVEN spacecraft allowed us to analyze densities of both neutrals and ions, providing insights into ion-neutral coupling in the upper atmosphere. As shown in Figure 5, we found that the rates of larger wavelengths enhanced during PEDE-2018 for both neutrals and ions (wavelengths are apparent along MAVEN trajectory, with a much larger horizontal than vertical scale). Moreover, high correlations among the wavelengths of various species (Figure 6, not shown here) were derived under both low-dust and PEDE-2018 conditions, may implying ion-neutral coupling and common dominant wave sources.
The Earth's upper atmosphere is the region between 100 and 1000 km in altitude where space stations, satellites, and rockets fly, and is considered the gateway to space. Because of its low density, it is a near-earth space region that exhibits complex behavior under the influence of both the sun and the lower atmosphere. It is a weakly ionized gas (plasma) due to ultraviolet radiation from the sun, and at the same time, it is a very dilute and hot atmosphere. The "ionosphere" is the name given to the weakly ionized gas, while the "thermosphere" is the name given to the dilute and hot atmosphere. The ionosphere has a direct impact on wireless communications, and the thermosphere has a direct impact on satellite orbits, so research in this area is called "space weather" and is closely related to modern social infrastructure. This research focuses on the three coupling processes in space weather with the keyword of "coupling between domains".
① Sun-driven space weather: Ionospheric and thermospheric disturbances caused by solar flares and large magnetic storms
② Atmosphere-Plasma Interaction in Weakly Ionized Media: Ionosphere-Thermosphere Coupling
③ Space weather driven by meteorological phenomena
The global fist motion of the thermospheric atmosphere associated with a large magnetic storm and a strong X17 class solar flare was shown from the observations of accelerometers onboard the satellite. The density variation of the thermospheric atmosphere associated with the magnetic storm and the propagation of the heated atmosphere in the polar region to the equatorial region were clarified. The thermospheric variability is considered to be a major contribution to space weather research because it shows the "diversity of the thermospheric atmosphere," which means that even if the external factors are the same, the subsequent variability depends on the state of the thermospheric atmosphere at that time.
The thermosphere, which is the neutral atmosphere that makes up most of the upper atmosphere, was generally believed to be "unaffected by magnetic fields. However, our papers published in 2005 and 2006 have changed this perception. By using the world's first high-precision accelerometer, which precisely measures gravity onboard a satellite, for thermospheric observations, we discovered anomalous thermospheric density anomalies (EMA) and thermospheric wind jets in the magnetic equatorial region. These discoveries revealed for the first time that the magnetic field dominates the behavior of the neutral atmosphere through atmosphere-plasma interaction, and provided a new perspective on thermospheric ionospheric dynamics. In addition, the accelerometer-based thermospheric observation method developed from our research has greatly stimulated research in the difficult-to-observe thermospheric region, and has become a pillar of upper atmosphere research in recent decades. This has stimulated research in the thermospheric region, which is difficult to observe.
In recent years, the study of atmospheric vertical coupling across the supercells and meteorological regions has made rapid progress due to the improved accuracy of ionospheric and thermospheric observations. Atmospheric waves originating from the lower atmosphere increase in amplitude as they propagate upward and decrease in atmospheric density, causing large fluctuations in the upper atmosphere (Fig. 2). For example, atmospheric tidal waves originating from the troposphere propagate up to several hundred kilometers above the surface, forming an ionospheric and thermospheric structure similar to the land/sea distribution of topography.(Paper 24,27)In addition, stratospheric sudden warming (SSW) causes ionospheric variability (ii, iii) and thermospheric cooling phenomena due to the interaction of planetary and tidal waves.(Paper 11,17,20,21)These studies suggest a spatio-temporal coupling between meteorological phenomena and cosmic phenomena at very high altitudes, and are being strongly promoted internationally as a new academic theme for global interdisciplinary research. We are also studying vertical coupling processes in the El Niño-Southern Oscillation, which is longer than the time scale, and in tropospheric convection, which is shorter.