Exploring the Sensitivity of Arctic Winter Climate to Aerosol Loading as Simulated in CMIP6

1 Introduction

The global near-surface atmospheric temperature (SAT) has increased over time since the 19^th century, and the most warming occurred in the recent decades after 1975 (Hansen et al., 2010; Morice et al., 2021; Craigmile and Guttorp, 2021). The recent warming over the land is more significant than that of the oceans, and the most affected regions are the high northern latitudes (Morice et al., 2021). In the Arctic, the average temperature north of 66.5°N has increased approximately four times more than the global increase between 1979 and 2021, referred to as Arctic amplification, though this warming difference differs by season and depends on the time period considered (Rantanen et al., 2022). Wendisch et al. (2023) also observed that the Arctic region north of 60°N has warmed faster than the lower latitudes between 20°S and 60°N, particularly in spring and winter, but this trend is less observed in summer. The enhanced Arctic warming is caused by many factors, including sea ice loss (Dai et al., 2019), enhanced heat and moisture transport in the atmosphere from the North Atlantic into the Arctic (Alekseev et al., 2020), and local climate feedbacks within the Arctic region (Block et al., 2020). Several reasons are behind the lower Arctic warming in summer, which mainly include the large heat uptake by the Arctic Ocean in summer and its release into the atmosphere in autumn and early winter (Laîné et al., 2016), as well as the larger increase in the evaporation rate over the ice-free Arctic lands in summer compared to winter (Laîné et al., 2016).

The recent global climate change is mainly caused by anthropogenic emissions of greenhouse gases (GHG) like carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) (Ciais et al., 2013). These gases modify the atmospheric energy balance by absorbing the upward long wave radiation and then emitting it in different directions (Kiehl and Trenberth, 1997). A part of the emission is directed downward, which reduces the heat loss from the surface and the lower atmosphere. Besides the GHGs, the anthropogenic emissions of aerosols have a significant impact on the global climate (Myhre et al., 2013). Atmospheric aerosols are liquid or solid particles suspended in the air that impact the climate through scattering and absorption of incoming solar radiation, as well as through interactions with terrestrial radiation via absorption and re-emission, referred to as the direct effect (Naik et al., 2021). Atmospheric aerosol also affects the climate indirectly by acting aerosol as cloud condensation nuclei (CCN, Twomey, 1974) and ice nucleating particles (INP, DeMott et al., 2010) through modifying the cloud micro- and macro-physical properties that are related to the cloud-radiation interactions like the cloud albedo. The effects of aerosols on the global climate differ by the aerosol type, but their overall impact, represented by the effective radiative forcing (${\text{ERF}}_{\text{aer}}$)—which includes both direct and indirect effects of the aerosols—is estimated as a cooling effect in the context of human-induced climate change reducing a part of the GHG warming, with uncertainties about the impact’s magnitude, which is estimated to be between –2.0 to –0.4 W m^–2 with a 90% likelihood in the period 2005 to 2015 compared to 1850 (Bellouin et al., 2020).

Several responses occur in the climate system due to the impacts of the anthropogenic emissions of GHG and aerosols on the climate. These responses include changes in water evaporation rates and alterations in the extent of sea ice and vegetation, which in turn affect surface albedo. Such changes can influence the atmospheric energy balance differently across various regions, seasons, and altitudes, leading to varying rates of cooling and warming (Mauritsen et al., 2013). Although climate change is globally observed, several studies have focused on specific regions due to their significant impacts and responses to climate change. One of these regions is the Arctic, which is experiencing some of the most pronounced warming effects of global climate change. The melting ice in Greenland contributes to rising global sea levels (Pritchard et al., 2009). Many studies on Arctic warming have revealed that various mechanisms contribute to this warming beyond the GHG forcing (Taylor et al., 2022; Previdi et al., 2021). For instance, Previdi et al. (2021) reported that aerosol forcing has been found to warm the Arctic SAT despite its cooling effect on the globe.

In addition to global climate change, there are natural fluctuations in the form of climate variability, individually known as modes of oscillations. One of these is the Arctic Oscillation (AO), which is presented as the leading mode of interannual atmospheric variability in the northern hemisphere (NH) (Thompson and Wallace, 2000). The AO plays a vital role in shaping the climate of the NH, particularly across the Arctic and mid-latitudes. Specifically, it has a profound impact on winter weather patterns (Thompson and Wallace, 2000). The phase and strength of the AO alter the position and intensity of the jet stream, thereby modulating the prevailing circulation and associated weather systems in the NH (Thompson and Wallace, 2000). In recent years, it has been evident that the AO index (AOI), which quantifies the phase and strength of the AO, has shifted toward more negative values (Maturilli and Kayser, 2017). Variability in the AO can influence the transport of heat and moisture into the Arctic from lower latitudes. This, in turn, can modify the lapse rate feedback (LRF), which refers to the change in temperature with altitude. The LRF is a crucial component of the climate system, especially in the Arctic regions, where it can amplify warming (Linke et al., 2023).

As a contributor to climate change, especially by warming the Arctic, studying the influence of aerosols on the AO is sparse. Using the community atmosphere model, Allen and Sherwood (2011) suggested that the aerosol enhancement could have influenced the AO. Qu et al. (2021) reported that volcanic aerosols strengthen the AO by intensifying the Arctic vortex system. Additionally, modeling studies have linked the Southeast Asian haze to the AO variability (e.g., Chung and Ramanathan, 2003). Moreover, increased aerosol loading in the Arctic can influence the lapse rate by altering the vertical distribution of heat (e.g., Calì Quaglia et al., 2022; Stone et al., 2008; Treffeisen et al., 2007), which in turn affects the ${\text{ERF}}_{\text{aer}}$ and the AO. Many studies, such as Salvi et al. (2022), have highlighted the sensitivity of LRF to aerosol changes, demonstrating that higher concentrations of aerosols can lead to changes in feedback mechanisms.

Despite the amplified Arctic warming observed in recent decades, the overall effect of aerosols on Arctic warming remains highly uncertain due to the distinctive geographical conditions and the various sources, types, and transport pathways of aerosols entering the Arctic. As a contributor to climate change, particularly in relation to Arctic warming, studying the influence of aerosols on the AO and the LRF provides valuable insights into how the aerosols affect the atmospheric circulation patterns in the NH and the sensitivity of the Arctic winter climate to these effects. This study, therefore, investigates the sensitivity of the Arctic winter climate to aerosol forcing using the Coupled Model Intercomparison Project 6 (CMIP6, Eyring et al., 2016). CMIP6 provides a comprehensive set of coordinated climate model experiments that include state-of-the-art representations of aerosol radiative effects, historical and projected forcing, and Arctic-relevant processes, making it particularly suitable for investigating the regional climate response. We quantify how ${\text{ERF}}_{\text{aer}}$ shapes the AO variability and LRF to determine the Arctic’s climate response. Focusing on boreal winter allows us to isolate the radiative effects and the dynamical atmospheric responses that are most relevant to the Arctic climate change. By linking aerosol forcing to atmospheric circulation and the LRF mechanism, this work aims to improve the understanding of aerosol impact and the sensitivity of the Arctic climate to this impact.

2 Data and Methods

3 Results

3.1 Effect of present-day aerosols on the Arctic climate

The ${\text{ERF}}_{\text{aer}}$ under present-day conditions in the winter season (DJF) shows a positive forcing in the Arctic relative to pre-industrial conditions (Figure 1). The estimated average ${\text{ERF}}_{\text{aer}}$ in the Arctic region, between 66°N and the North Pole, is approximately 0.14 W m^–2 (Table A.2). This positive ${\text{ERF}}_{\text{aer}}$ over the Arctic can be attributed to the increased aerosol load resulting from the transport of aerosols from lower latitudes (Figure A.1). The enhanced present-day aerosol loading, relative to pre-industrial levels (as of the year 1850), interacts with the dominant long wave (LW) radiation during the polar winter, effectively reducing the amount of outgoing LW radiation at the TOA, which leads to positive ${\text{ERF}}_{\text{aer}}$ and consequent surface warming (Zhou and Savijärvi, 2014). In addition to the Arctic, the positive ${\text{ERF}}_{\text{aer}}$ persists over the Sahara and large regions in central and northern Eurasia with high surface albedo. In contrast to most of the Arctic and other snow-covered areas, the present-day aerosol results in a negative ${\text{ERF}}_{\text{aer}}$ over Greenland and the adjoining region. During winter, the primary pathway for aerosol transport to much of the Arctic, particularly the Eurasian sector, is through low-level transport from Eurasia (Law et al., 2014). However, this transport does not reach Greenland due to the positioning of the Arctic front and the prevailing transport from the North American region (Law et al., 2014). In addition, the high elevation of Greenland limits the efficiency of low-level aerosol transport to its interior, as discussed by Guy et al. (2021). They showed that when air masses are advected from the coast and surrounding ocean and forced to ascend the elevated topography, orographic lifting induces adiabatic cooling, cloud formation, and precipitation, which together enhance aerosol removal through wet deposition. Consequently, aerosol concentrations over Greenland decrease during such upslope flow events, particularly under anomalous cyclonic circulation over southeast Greenland, which occurs more frequently in winter (Guy et al., 2021; Schuenemann et al., 2009). At lower latitudes, the negative ${\text{ERF}}_{\text{aer}}$ is more dominant, with the average ${\text{ERF}}_{\text{aer}}$ in the NH between 20°N and 66°N being approximately –0.91 W m^–2 (Table A.3). Overall, the mean ${\text{ERF}}_{\text{aer}}$ for the NH domain from 20°N to 90°N is approximately –0.79 W m^–2 (Table A.1), reflecting the significantly larger magnitude of the negative forcing at mid- and low latitudes relative to the positive forcing in the Arctic (Figure 1).

Figure 1

The increase in atmospheric aerosols over the NH and its impact on the ERF have, in turn, modified the AO (Figure 2). It shows significant positive SLP anomalies in the Arctic region, which extend even into northern North America. In contrast, negative SLP anomalies are prevalent in the northern Atlantic, northern Pacific, most of the United States, and north and central Eurasia. These changes in SLP result in a positive anomaly in AOI in piClim-aer compared to piClim-control (Figure 3). Similar findings were reported by Zanis et al. (2020), who demonstrated that aerosol-induced circulation changes exhibit a characteristic dipole pattern, characterized by the intensification of the Icelandic low and an anticyclonic anomaly over southeastern Europe.

Figure 2

Figure 3

3.2 Transient effect of aerosols

3.2.1 Aerosol loading and its impact on radiative forcing

The temporal variation of the mean aerosol optical depth (AOD) in NH (20°N–90°N) during the winter is illustrated in Figure 4a. The AOD has shown an increasing trend since 1850, peaking in the second half of the 20^th century (AOD ≈ 0.15). Later, it decreases toward the end of the 21^st century (AOD ≈ 0.1). The ${\text{ERF}}_{\text{aer}}$ also shows a similar pattern, increasing from 1850 toward the end of the 21^st century (Figure 4b). A negative ${\text{ERF}}_{\text{aer}}$ indicates that aerosol loading in the NH results in net cooling at TOA. This increase in aerosol-induced cooling is reversed in the second half of the 20^th century due to the reduction in aerosol concentrations (Figure 4a and b). The most significant changes in ${\text{ERF}}_{\text{aer}}$ occurred between 1970 and 1980, contributing to an increase in the upward SW radiation at TOA (Figure A.2a), which also peaks at the same time and exceeds 1.5 W m^–2. Meanwhile, upward LW radiation at TOA shows negative anomalies on average between 1900 and 2050, reaching a maximum reduction of approximately 0.7 W m^–2 between 1970 and 1980 (Figure A.2b), corresponding to a positive radiative forcing. However, this reduction in LW radiation does not offset the contribution from increased SW radiation in the context of net negative ${\text{ERF}}_{\text{aer}}$.

Figure 4

Likewise, in the Arctic region (66°N to 90°N), changes in AOD are qualitatively similar to those observed in the NH. There was a significant increase in aerosol burden between 1970 and 1980, indicating enhanced aerosol transport to the Arctic region (Figure 4c). The ${\text{ERF}}_{\text{aer}}$ in the Arctic fluctuates between positive and negative values, as depicted in Figure 4d. However, the 30-year moving average demonstrates that the ${\text{ERF}}_{\text{aer}}$ has been negative since 1920, reaching its lowest point between 1970 and 1980, in line with the AOD trends. Unlike the ${\text{ERF}}_{\text{aer}}$ in the NH, the variation in the winter ${\text{ERF}}_{\text{aer}}$ over the Arctic is mainly influenced by changes in the upward LW (Figure A.3b), which are stronger in magnitude than the changes in upward SW (Figure A.3a), highlighting the key role of LW radiative processes in modulating the Arctic energy budget in response to aerosol forcing. The negative ${\text{ERF}}_{\text{aer}}$ and increased outgoing LW flux at TOA indicate a net cooling at TOA, but do not directly describe surface temperature changes. Due to aerosol-induced modifications of the AO and LRF, energy can be redistributed within the Arctic column, and surface warming in winter can coexist with negative ERF and increased outgoing LW flux at TOA, as shown later in Sections 3.2.2. and 3.3.

The above analysis highlights the significant role that aerosols play in the Arctic climate and its variability. However, our understanding of how sensitive the changes in the Arctic climate are to aerosols is still limited. For this, we have examined periods of low and high aerosol loading based on transient simulations. The temporal distribution of AOD in the transient simulations indicates a peak between 1965 and 2014, specifically around 1988, while showing minimal AOD loading between 1851 and 1900 (50 years each). We have therefore designated these periods as high and low aerosol loading scenarios, respectively, to examine the aerosol sensitivity to the Arctic climate.

While it may be tempting to simplify the analysis by comparing only the pre-industrial conditions represented by the piClim-control (1850) with the high-aerosol period (1965–2014), our choice to include the early industrial low-aerosol period (1851–1900) is deliberate. This interval captures the initial rise in anthropogenic aerosol emissions while still representing a period of relatively low aerosol concentrations. Including it enables us to assess how the Arctic responds to any changes in aerosol loading. It also gives us an intermediate forcing level, allowing us to see how the Arctic responds to incremental changes, not only to the most substantial aerosol forcing. This approach allows us to examine whether the climate response increases linearly, slows down, levels off, or even reverses beyond certain forcing thresholds—insights that would be missed by comparing only zero versus maximal forcing. In this way, the early industrial period provides an informative ‘middle ground’ that strengthens the robustness of our sensitivity estimates and enhances our understanding of aerosol-climate interactions in the Arctic.

3.2.2 Aerosol-sensitivity of Arctic Oscillation (AO)

Figure 5 illustrates the distribution of the AOI for high and low aerosol loading scenarios. The figure shows that the AOI distribution is positively skewed compared to piClim-control for both aerosol conditions. This skewness suggests a relative decrease in SLP over the Arctic and an increase in mid-latitude SLP. The positively skewed AOI distribution indicates a stronger polar vortex and a more stable jet stream, which reduces the frequency and intensity of Arctic air incursions into mid-latitudes (Limpasuvan and Hartmann, 2000), suggesting a substantial aerosol impact on the Arctic climate. However, the sensitivity of the AOI to aerosols shows less influence on the extreme AOI distributions (90^th and 10^th percentile). The variability in the AOI induced by aerosols suggests that aerosol forcing could moderate AOI variability, resulting in a more constrained range of AO patterns. This has important implications for winter climate variability in the NH. From the AOI distribution, the estimated AOI anomaly illustrates that the anomaly is larger (0.25) for the low aerosol conditions compared to the high aerosol scenario, which has an anomaly of 0.1. This suggests that changes in the AO are driven by varying aerosol concentrations, leading to significant effects on both regional and global climates despite the magnitude of the sensitivity to aerosols.

Figure 5

A marked difference is evident between the AOI probability density functions (PDFs) during the piClim-histaer periods (Figure 5) and the AOI PDF in piClim-aer (Figure 3). This difference primarily arises from how aerosol forcing is represented in the two simulations. piClim-aer uses fixed present-day aerosol concentrations (as of 2014) throughout the simulation. This idealized setup imposes a steady radiative forcing, so the atmosphere settles into a relatively stable circulation response. In contrast, piClim-histaer includes the historical evolution of aerosols, capturing the rise and fall of aerosol emissions over time, which drives stronger variability in AO and thus changes the AOI distribution more.

Figure 6 illustrates the SAT anomalies for the low and high aerosol loading scenarios. The magnitude of temperature changes across the NH varies between periods. In both cases, an increase in the SAT is noticed over Eurasia and western North America, while temperatures mainly decrease in most lower latitude regions. Notably, in the high aerosol scenario, SAT warming is concentrated in the Arctic region, with temperature increases of up to approximately 1 K. However, warming in the Arctic region is less dominant in the low aerosol scenario. Importantly, the strong warming is localized over the Arctic in the high-aerosol scenario, creating a pronounced temperature gradient toward the lower latitudes. The profound changes in the Arctic and associated climate variability (AO) are also accompanied by variations in extreme weather events in the mid-latitudes, as extreme weather events are typically linked to the phase of the AO. Figure 7 illustrates the aerosol sensitivity to extreme SAT (90^th and 10^th percentile) during the positive AO phase. During this positive AO phase, the 10^th percentile of the SAT anomaly shows positive values over most of the NH for both low and high aerosol loading scenarios (Figure 7a and b). It indicates that the aerosol enhancement leads to less extreme cold winters. This less extreme cold winter is more pronounced in the high aerosol loading scenario, especially over the Arctic, compared to the low aerosol scenario. On the other hand, the anomalies of the 90^th percentile of annual winter temperatures are negative across most of the NH in both periods (Figure 7c and d), except for the Arctic. From the figure, it is seen that there is a strong aerosol sensitivity to Arctic warming, indicating that enhanced aerosol loading in the high aerosol scenario results in strong positive SAT anomalies (90^th percentile), particularly in the Arctic region, where extreme SAT has increased by up to 1.5 K. It suggests that aerosol enhancement leads to warmer winters in the Arctic. Furthermore, the significant changes in the SAT and AO also affect the position of jet streams, which influences the storm tracks and the magnitude and intensity of cold/warm air spells. Figure 8 illustrates the latitudinal position of the jet stream during the positive AO phase and its relation to the aerosol enhancement. During the positive AO phase, the jet stream shifted southerly, with the most significant shifts occurring in the high aerosol scenario. This southern shift of the jet stream during the positive AO phase reflects the weakened positive phase, with moderate impacts associated with the AO on the climate of mid-latitudes.

Figure 6

Figure 7

Figure 8

Similarly, during the negative AO phase, 10^th percentile SAT anomalies are positive over the NH, irrespective of the aerosol loading scenario. However, the magnitudes of these anomalies do not significantly differ between the two periods (Figures 9a and b), unlike the variations seen in the positive AO phase. In addition, some negative SAT anomalies are observed over Greenland, western North America, and the Mediterranean in the low aerosol scenario. Conversely, the anomalies of the 90^th percentile of annual winter temperatures are negative over most of the NH during both periods (Figure 9c and d). However, positive SAT anomalies appear in parts of Eurasia and the Arctic during the high aerosol scenario, similar to that observed in the positive AO phase. Moreover, during the negative AO phase, the position of the jet stream has been shifted northward in both low and high aerosol scenarios (Figure 10). It is important to note that aerosol enhancement is less sensitive to this northward shift of the jet stream.

Figure 9

Figure 10

3.3 Aerosol-sensitivity of lapse rate feedback (LRF)

In the Arctic, the vertically non-uniform warming of the troposphere results in a positive LRF, which has been identified as the contributor to Arctic amplification. The above analysis indicates that increased aerosol concentration significantly warms the Arctic. Likewise, the LRF is also sensitive to aerosol enhancement. Figure 11 illustrates the spatial distribution of LRF for low and high aerosol scenarios. In the high aerosol scenario, a strong positive LRF is observed over the Arctic and the adjoining regions, specifically over northern Eurasia and northern North America. In contrast, during the low aerosol scenario, a strong positive LRF appears only in a few regions of northern Eurasia and northwest North America. In the Arctic, the pronounced positive LRF correlates with the enhancement of aerosol loading. Conversely, during the high aerosol scenario, negative feedback affects a broader area across the continents at lower latitudes, showing higher absolute values compared to the low aerosol scenario. The positive LRF over the Arctic can be attributed to a greater warming near the surface compared to the upper troposphere, as illustrated in Figure 12. This warming has intensified during the high aerosol scenario, likely due to increased aerosol loading that reduces outgoing LW radiation during the polar night, trapping more heat near the surface. In contrast, the negative LRF at lower latitudes is associated with warming the upper troposphere that exceeds the relatively limited surface warming in some regions and even contrasts with surface cooling in others (Figure 12).

Figure 11

Figure 12

4 Summary and Conclusions

We conducted a comprehensive analysis of the impact of aerosol forcing on the Arctic climate during the winter, utilizing data from CMIP6 models. The study focuses on understanding the role of aerosols in Arctic warming/cooling and its consequences on the Arctic climate variability, specifically AO. The study also delved into how aerosol transport into the Arctic region affects the LRF.

The present-day aerosol induces a positive ${\text{ERF}}_{\text{aer}}$, particularly in the Arctic, compared to pre-industrial conditions during winter (DJF). The estimated average ${\text{ERF}}_{\text{aer}}$ in the Arctic region is approximately 0.14 W m^–2, which is linked to enhanced aerosol loading resulting from strong transport from Eurasia and adjoining regions. This enhanced aerosol loading reduces the amount of outgoing LW radiation at the TOA, causing positive ${\text{ERF}}_{\text{aer}}$ and warming in the region. However, a significant negative ${\text{ERF}}_{\text{aer}}$ of approximately –0.91 W m^–2 is simulated at lower latitudes (between 20°N and 66°N) due to an increase in upward SW radiation caused by aerosol reflection. Furthermore, our analysis suggests that the enhanced aerosol loading and subsequent warming in the Arctic have a considerable impact on the AO. The positive aerosol ${\text{ERF}}_{\text{aer}}$ leads to significant positive SLP anomalies over the Arctic, which extend into northern North America, while negative SLP anomalies dominate in other parts of the NH. Importantly, the increase in aerosols has resulted in a positively skewed distribution of the AOI compared to the control simulation (piClim-control).

Similar to the present-day ${\text{ERF}}_{\text{aer}}$, the transient simulations also demonstrate a significant impact on the ${\text{ERF}}_{\text{aer}}$. However, aerosol concentrations exhibit considerable global and temporal variability. In the NH, the aerosol concentrations were at their lowest between 1850 and 1900. They then increased over time, peaking between 1964 and 2014, before declining to their minimum levels by the end of the century. Thus, to assess the sensitivity of aerosol loading in the Arctic climate, we compared periods of low and high aerosol emissions, specifically within the NH. During the high aerosol scenario, the SAT warming is concentrated in the Arctic region with a magnitude of anomaly up to ≈ 1 K from the pre-industrial conditions. In contrast, the Arctic is less affected by warming during the low aerosol scenario. In both low- and high-emission scenarios, the AOI distribution is positively skewed, indicating that variations in aerosol concentrations drive changes in the AO, leading to a predominance of its positive phase, which indicates a strengthened polar vortex and a more stable jet stream. However, the AOI distribution is less sensitive to the enhancement of aerosols. Consequently, the increased aerosol loading and its relationship to the AO may contribute to fluctuations in extreme weather. Our analysis indicates that aerosol enhancement results in extremely warm winters in the Arctic, in contrast to most of the NH, irrespective of the phase of the AO. Additionally, during the positive AO phase, the enhancement of aerosols causes the jet stream to shift southward, while it moves northward during the negative AO phase.

Furthermore, the positive LRF arises from the vertically non-uniform warming of the troposphere, which contributes to the amplification of the Arctic SAT. Our analysis indicates that aerosol enhancement leads to an increase in positive LRF in the Arctic. The enhanced positive LRF over the Arctic can be attributed to more significant warming near the surface compared to the upper troposphere, which is associated with the high aerosol scenario.

Our analysis suggests that aerosol loading has a substantial effect on the Arctic climate. Specifically, the present-day aerosol loading over the Arctic leads to a positive ${\text{ERF}}_{\text{aer}}$, implying surface warming during winter (DJF). Furthermore, aerosol-induced warming in the Arctic region also affects climate variability, especially the AO. The LRF, which acts as a positive feedback in the Arctic and plays a crucial role in Arctic amplification by enhancing SAT responses to radiative forcing under human-induced climate change, is further influenced by aerosol enhancement. However, the quantification and future projections of the effect of aerosols on the Arctic climate remain highly uncertain due to the spatial and temporal variability of aerosols. A better understanding of the ${\text{ERF}}_{\text{aer}}$ is essential for constraining the impact of aerosols on the Arctic climate and its associated variability, including the AO and related impacts, such as climate extremes. Furthermore, future studies could extend this work by exploring the indirect effects of aerosol-cloud interactions, which may further modulate the Arctic energy balance and feedback processes.

Data Accessibility Statement

All CMIP6 RFMIP model data used in this study were obtained from the Earth System Grid Federation (ESGF, https://esgf.llnl.gov/). The variables analyzed include: psl, tas, ta, rsdt, rsut, rlut, ua, and va. Radiative kernel datasets were obtained from Huang, Han; Huang, Yi (2023a), Data for ERA5 radiative kernels, Mendeley Data, V4, doi: 10.17632/vmg3s67568.4, available at https://data.mendeley.com/datasets/vmg3s67568/4. Processed datasets generated in this study are available from the corresponding author upon reasonable request.

Code Availability Statement

The analysis and plotting code used in this study is available from the corresponding author upon reasonable request.

Competing Interests

The authors have no competing interests to declare.

Author Contributions

K.A. designed the study, performed the calculations and plotting, conducted the analysis, and drafted the manuscript. S.D. supervised the work and contributed to the analysis, writing and revising the manuscript. All other authors provided comments and contributed to revising the manuscript.