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Surface solar radiation is fundamental for terrestrial life. It provides warmth to make our planet habitable, drives atmospheric circulation, the hydrological cycle and photosynthesis. Europe has experienced an increase in surface solar radiation, termed "brightening," since the 1980s. This study investigates the causative factors behind this brightening. A novel algorithm from the EUMETSAT satellite application facility on climate monitoring (CM SAF) provides the unique opportunity to simulate surface solar radiation under various atmospheric conditions for clouds (clear‐sky or all‐sky), aerosol optical depth (time‐varying or climatological averages) and water vapor content (with or without its direct influence on surface solar radiation). Through a multiple linear regression approach, the study attributes brightening trends to changes in these atmospheric parameters. Analyzing 61 locations distributed across Europe from 1983 to 2020, aerosols emerge as key driver during 1983–2002, with Southern Europe and high elevations showing subdued effects (0%/decade–1%/decade) versus more pronounced impacts in Northern and Eastern Europe (2%/decade–6%/decade). Cloud effects exhibit spatial variability, inducing a negative effect on surface solar radiation (−3%/decade–−2%/decade) at most investigated locations in the same period. In the period 2001–2020, aerosol effects are much smaller, while cloud effects dominate the observed brightening (2%/decade–5%/decade). This study therefore finds a substantial decrease in the cloud radiative effect over Europe in the first two decades of the 21st century. Water vapor exerts negligible influence in both sub‐periods. Plain Language Summary: This study explores the recent increase in surface solar radiation in Europe, commonly referred to as "brightening," which began in the mid‐1980s. Surface solar radiation is crucial for life on Earth, fostering warmth, shaping wind patterns, and fueling the hydrological cycle and photosynthesis. Utilizing data derived from satellites, we simulated surface solar radiation under different atmospheric conditions regarding clouds, aerosols, and water vapor. This allowed us to separate the individual effects and analyze their contributions to the observed brightening across 61 locations in Europe from 1983 to 2020. We find that the decrease in aerosols was the dominant driver for the brightening during the initial period from 1983 to 2002. Southern Europe and high‐elevation areas showed modest aerosol effects, while Northern and Eastern Europe experienced higher values. Cloud effects were predominantly negative (decreasing surface solar radiation) at most locations. However, between 2001 and 2020 the aerosol effect resulted much smaller and the brightening was mostly attributed to a decrease in cloudiness during that sub‐period. Water vapor was found to have a negligible impact on surface solar radiation trends. Key Points: Satellite application facility on climate monitoring (CM SAF) Land Flux v1.0 surface solar radiation data agree well with station‐based measurements over Europe, also at high‐altitude locationsThe direct aerosol effect was the main driver of the European brightening from 1983 to 2002. Changes in cloudiness rather counteracted itFrom 2001 to 2020 the brightening in Europe was dominated by the cloud effect and the aerosol effect resulted much smaller [ABSTRACT FROM AUTHOR]

Numerous studies have investigated the long-term variability in surface solar radiation (SSR) around the world. However, the large disparity in the availability of observational data between developed and less developed/developing countries leads to an under-representation of studies on SSR changes in the latter. This is especially true for South America, where few observational studies have investigated the SSR trends and usually only at a local or regional scale. In this study we use data from 34 stations distributed throughout all of the regions of Brazil to present the SSR trends in the first 2 decades of the 21st century and investigate their associated causes. The stations were grouped into eight composites according to their proximity. Our results show that in north and northeast Brazil a strong dimming occurred, with significant contributions from increasing atmospheric absorption, most likely due to anthropogenic emissions, and increasing cloud cover. In the southeast and midwest regions of Brazil, near-zero trends resulted from competing effects of clear-sky processes (attenuation of solar radiation under cloudless conditions) and strong negative trends in cloud cover. In the southern part of the Amazon and in south Brazil a statistically insignificant brightening was observed, with significant contributions from decreasing biomass burning emissions in the former and competing minor contributions in the latter. These results can help deepen our knowledge and understanding of SSR long-term trends and their causes in South America, reducing the under-representation of this continent when compared with regions like Europe. [ABSTRACT FROM AUTHOR]

Downward long-wave irradiance (DnLWI) is a variable that directly influences the surface net radiation, which in turn affects weather and climate. Due to the lack of abundant DnLWI observations, numerical weather prediction (NWP) models provide a very effective way to yield the DnLWI. Nevertheless, the reliability of the DnLWI predicted by the NWP models needs the evaluation based on the observations or accurate radiative transfer models. In this study, the DnLWI product of the China Meteorological Administration mesoscale model (CMA-MESO) was extensively validated using long-term high time-resolution (1 min) DnLWI measurements carried out at 42 sites in China. The results showed that the DnLWIs predicted by the CMA-MESO model generally agreed well with the observations, i.e., with a relative mean bias error (rMBE) of –2.0 %, but overestimated them under overcast (3.1 %) and underestimated them under dry (–5.3 %) and cloudless (–5.2 %) conditions. It is also found that the discrepancies in the DnLWI predicted by the CMA-MESO model exhibited spatial and diurnal variations, e.g., the discrepancies were significantly smaller at night than those during the day due to the stable nocturnal boundary layer. According to the results of the partial least squares analysis, the high cloud cover, medium cloud cover, planetary boundary layer height, and integrated cloud ice were the most important factors affecting the accuracy of the DnLWIs predicted by the CMA-MESO model under all sky conditions. By comparing the outputs of the CMA-MESO model and the MODerate resolution atmospheric TRANsmission (MODTRAN) model, it was found that the uncertainties in the DnLWI predicted by the CMA-MESO model mainly arose from an inappropriate consideration of the high and medium clouds under all sky conditions as well as shortcomings in the radiation scheme under cold dry cloudless conditions. [ABSTRACT FROM AUTHOR]

The variability of the shortwave radiative fluxes at the surface and top of atmosphere (TOA) is examined in a pre‐industrial modeling setup using the Pacific Decadal Oscillation (PDO) as a possible pacemaker of atmospheric decadal‐scale variability. Within models from the Coupled Model Intercomparison Project—Phase 6, downwelling shortwave radiation at the surface, the net shortwave fluxes at the surface and TOA, as well as cloud radiative effects show remarkably similar patterns associated with the PDO. Through ensemble simulations designed with a pure PDO pattern in the North Pacific only, we show that the PDO relates to about 20%–40% of the unforced year‐to‐year variability of these shortwave fluxes over the Northern Hemispheric continents. The sea surface temperature imprint on shortwave‐flux variability over land is larger for spatially aggregated time series as compared to smaller areas, due to the blurring effect of small‐scale atmospheric noise. The surface and TOA radiative flux anomalies associated with the PDO index range of [−1.64; 1.64] are estimated to reach up to ±6 Wm−2 for North America, ∓3 Wm−2 for India and ±2 Wm−2 for Europe. We hypothesize that the redistribution of clouds in response to a North Pacific PDO anomaly can impact the South Pacific and North Atlantic SSTs. Plain Language Summary: We investigate how solar radiation at Earth's surface and the top of the atmosphere, which are mainly controlled by cloudiness, can vary over decades as a response to a horseshoe pattern typical for the North Pacific sea surface temperatures (SSTs)—the Pacific Decadal Oscillation (PDO). We use idealized climate model simulations to show that about a third of the year‐to‐year changes in solar radiation over the Northern Hemispheric continents are related to this phenomenon. These changes are more noticeable when looking at large areas rather than small ones, as high frequency smaller scale atmospheric variations can obscure the bigger picture. By keeping the PDO fixed to a constant negative value, implying below average cold sea surface temperatures off the western coast of North America and warmer than average temperatures toward Japan, we show that North America and Europe exhibit a reduction in cloudiness, while clouds increase in India. The same with an opposite sign is true for a positive PDO anomaly. These changes in cloud patterns might further affect SSTs in the South Pacific and North Atlantic oceans. Key Points: The Pacific Decadal Oscillation (PDO) is a prominent pacemaker for variability, accounting for about 1/3 of the shortwave flux year‐to‐year variability over NH continentsA negative PDO anomaly leads to a reduction in atmospheric shortwave reflectivity (clouds) in North America and Europe and an increase in IndiaThe redistribution of clouds in response to a North Pacific PDO anomaly might influence SSTs in the South Pacific and North Atlantic [ABSTRACT FROM AUTHOR]

Extending across seven countries, the Alps represent an important element for climate and atmospheric circulation in Central Europe. Its complex topography affects processes on different scales within the atmospheric system. This is of major relevance for the decadal trends in surface solar radiation (SSR), also known as periods of global dimming and brightening (GDB). In this study we analyzed data from 38 stations in and around the Swiss and Austrian Alps, over a period ranging from the 1980s up to the 2020s, with the aim of characterizing the spatio‐temporal variations of the GDB and understanding the causes for such trends in this region. Our results show a different behavior in the SSR decadal trends in the western part of the Alps in comparison to the eastern part. Our results also suggest a remarkable difference between the causes of such trends at the stations at low altitudes in comparison to the stations at higher altitudes. Significant contributions from changes in cloud optical depth and surface albedo to the SSR decadal trends at high elevation sites were also found, in contrast to a substantial clear‐sky forcing that strongly dominates at low elevations. Results from previous literature and available data suggest that cloud optical depth changes at high altitudes and clear‐sky forcing at low altitudes could be associated with the indirect and direct aerosol effects, respectively, due to differing pollution levels at low and high elevation sites. Plain Language Summary: The incidence of surface solar radiation (SSR) is not constant, nor spatially homogeneous over decades around the globe. It undergoes trends, also known as Global Dimming (negative) or Brightening (positive). Such trends can have different causes, such as changes in cloudiness and aerosol concentrations. In regions with complex topography, like the Alps, understanding the processes leading to such trends might be challenging. In this study we investigated the causes of decadal trends in SSR at 38 stations in the Alpine region. The results show distinctly different decadal trends in SSR between the stations in the western and those in the eastern part of the Alps. We also identified that altitude plays a major role for the causes of the trends. While at low elevations changes in aerosol concentrations seem to largely affect long‐term SSR, at high altitude stations the changes in surface reflectivity and optical properties of clouds seem to also significantly contribute. This latter effect might be, however, also associated with changes in aerosol concentrations, since the amount of aerosols present in the cloud formation process significantly affects the cloud optical properties. Key Points: Stations from the western and eastern Alps show different signs and transition periods in decadal trends of surface solar radiation (SSR)Low elevation stations in the Alpine region show strong clear‐sky trends, likely associated with changes in aerosol emissions in EuropeEvidence suggests that changes in cloud optical depth and surface albedo can also contribute to the SSR decadal trends at high elevations [ABSTRACT FROM AUTHOR]

The downward surface longwave flux (DSLF) plays a relevant role in the Earth's surface radiative budget, which is crucial to monitor, understand and model the impact of changes at local and global scales on surface temperature and surface conditions. This study focuses on the evaluation and intercomparison of four DSLF products: (a) a recently developed all‐weather DSLF product based on the multivariate adaptive regression splines (MARS) algorithm driven by satellite cloud information from the Meteosat Second Generation (MSG) and ERA5 reanalysis screen variables; (b) the Satellite Application Facility on Land Surface Analysis (LSA SAF); (c) CERES Synoptic top‐of‐atmosphere and surface fluxes and clouds (CERES‐SYN1deg) and (d) ERA5 reanalysis. The study covers the period 2005–2021 and the MSG region focusing on monthly means. The evaluation performed against 48 ground stations from the Baseline Surface Radiation Network (BSRN) and FLUXNET2015 networks showed that the MARS product outperforms the remaining products, particularly the LSA SAF, while ERA5 and CERES show similar performance metrics. The fours products are intercompared in terms of their mean spatial variability and temporal mean annual cycles and inter‐annual variability in four selected regions, showing a high level of agreement, particularly between MARS, ERA5 and CERES. Our results highlight the clear added value of MARS with respect to LSA SAF, while providing higher spatial resolution (0.05°), constrained by satellite cloud information, when compared with ERA5 (0.25°) or CERES (1°). Plain Language Summary: Radiation that reaches the Earth's surface is fundamental for our understanding of the Earth's energy balance. In this work, we use a complex mathematical method together with data from weather satellites and ground‐based instruments to estimate the heat radiation component. To evaluate our results, we perform a comparison with those from various existing methods, including the one used by the Portuguese meteorological service. Our method generally outperforms the already existing techniques, with small errors as compared to surface measurements, demonstrating the added value of this new approach in improving our understanding of Earth's energy budget. Key Points: Evaluation of a new high spatial (0.05°) and temporal (30 min) resolution DSLF product constrained by MSG satellite cloud informationThe new DSLF MARS product outperforms the current LSA SAF when evaluated against 48 ground stationsHigh level of spatial and temporal variability consistency between four DSLF products MARS, LSA SAF, ERA5, CERES [ABSTRACT FROM AUTHOR]

Numerous studies have investigated the long term variability of surface solar radiation (SSR) around the world. However, the large disparity in the availability of observational data between developed and least developed/developing countries leads to an underrepresentation of studies on SSR changes in the latter. This is especially true for South America, where few observational studies have investigated the SSR decadal trends, and usually only at a local or regional scale. In this study we use data from 34 stations distributed throughout all the regions of Brazil to present the decadal SSR decadal trends in the first two decades of the 21st century and investigate their associated causes. The stations were grouped into 8 composites according to their proximity. Our results show that in the North and Northeast Brazil a strong dimming occurred, with significant contributions from increasing atmospheric absorption, most likely due to anthropogenic emissions, and increasing cloud cover. In the Southeast and Midwest regions of Brazil near-zero trends resulted from competing effects of clear-sky processes and strong negative trends in cloud cover. In the South part of the Amazon and in Southern Brazil a statistically insignificant brightening was observed, with significant contribution from decreasing biomass burning emissions in the former and competing minor contributions in the latter. These results can contribute to deepen the knowledge and understanding of SSR decadal trends and their causes in South America, reducing the underrepresentation of this continent when compared to regions like Europe. [ABSTRACT FROM AUTHOR]

Numerous studies have investigated the long term variability of surface solar radiation (SSR) around the world. However, the large disparity in the availability of observational data between developed and least developed/developing countries leads to an underrepresentation of studies on SSR changes in the latter. This is especially true for South America, where few observational studies have investigated the SSR decadal trends, and usually only at a local or regional scale. In this study we use data from 34 stations distributed throughout all the regions of Brazil to present the decadal SSR decadal trends in the first two decades of the 21st century and investigate their associated causes. The stations were grouped into 8 composites according to their proximity. Our results show that in the North and Northeast Brazil a strong dimming occurred, with significant contributions from increasing atmospheric absorption, most likely due to anthropogenic emissions, and increasing cloud cover. In the Southeast and Midwest regions of Brazil near-zero trends resulted from competing effects of clear-sky processes and strong negative trends in cloud cover. In the South part of the Amazon and in Southern Brazil a statistically insignificant brightening was observed, with significant contribution from decreasing biomass burning emissions in the former and competing minor contributions in the latter. These results can contribute to deepen the knowledge and understanding of SSR decadal trends and their causes in South America, reducing the underrepresentation of this continent when compared to regions like Europe. [ABSTRACT FROM AUTHOR]

The New Baseline Surface Radiation (NBSR) system was established at the Shangdianzi (SDZ) regional Global Atmosphere Watch (GAW) station in 2013 to observe nine broadband radiation components, i.e. the global, direct, diffuse, and upwelling shortwave irradiance (GSWI, DSWI, DifSWI, and UpSWI); the photosynthetically active radiation (PAR); the ultraviolet irradiance (UVAI and UVBI); and the down- and upwelling longwave irradiance (DnLWI and UpLWI). To test the 1 min raw radiometric data, a Hybrid Algorithm for Radiation Data Quality Control (HARDQC) is presented in this study based on well-established methods, together with the solar irradiance dataset and the spectral features of the instrument bands. Subsequently, a NBSR dataset, which consists of radiation data at multiple timescales (i.e. 1 min, hourly, daily, monthly, monthly average hourly, and monthly average daily) over 2013–2022, is established and evaluated. Results show that more than 98.7 % of all radiation components passed the physical possibility test. The percentages of those that passed the extremely rare test are greater than 98.6 % for all radiation components except for the DnLWI (97.1 %). The percentages of those that passed the comparison test are greater than 83.3 % (GSWI), 78.3 % (DSWI), 81.7 % (DifSWI), 93.1 % (UpSWI), 88.9 % (PAR), 95.6 % (UVAI), 96.3 % (UVBI), 99.8 % (DnLWI), and 99.7 % (UpLWI), respectively. Due to data logger faults, removal of the instruments for calibration, and lightning strikes, some apparent data gaps in the upwelling radiation components (January 2015–August 2017) and all radiation components (December 2018; July to September 2021) were detected. Despite the existence of a few imperfections in the NBSR dataset, it is still reliable to apply it in many fields such as the validation of satellite products and numerical models, the investigation of relationships between radiation and atmospheric composition, and the detection of changes in the surface fluxes. The dataset described in this paper is available at 10.1594/PANGAEA.963330 (Quan et al., 2023b). [ABSTRACT FROM AUTHOR]

Scientific innovation is overturning conventional paradigms of forest, water, and energy cycle interactions. This has implications for our understanding of the principal causal pathways by which tree, forest, and vegetation cover (TFVC) influence local and global warming/cooling. Many identify surface albedo and carbon sequestration as the principal causal pathways by which TFVC affects global warming/cooling. Moving toward the outer latitudes, in particular, where snow cover is more important, surface albedo effects are perceived to overpower carbon sequestration. By raising surface albedo, deforestation is thus predicted to lead to surface cooling, while increasing forest cover is assumed to result in warming. Observational data, however, generally support the opposite conclusion, suggesting surface albedo is poorly understood. Most accept that surface temperatures are influenced by the interplay of surface albedo, incoming shortwave (SW) radiation, and the partitioning of the remaining, post‐albedo, SW radiation into latent and sensible heat. However, the extent to which the avoidance of sensible heat formation is first and foremost mediated by the presence (absence) of water and TFVC is not well understood. TFVC both mediates the availability of water on the land surface and drives the potential for latent heat production (evapotranspiration, ET). While latent heat is more directly linked to local than global cooling/warming, it is driven by photosynthesis and carbon sequestration and powers additional cloud formation and top‐of‐cloud reflectivity, both of which drive global cooling. TFVC loss reduces water storage, precipitation recycling, and downwind rainfall potential, thus driving the reduction of both ET (latent heat) and cloud formation. By reducing latent heat, cloud formation, and precipitation, deforestation thus powers warming (sensible heat formation), which further diminishes TFVC growth (carbon sequestration). Large‐scale tree and forest restoration could, therefore, contribute significantly to both global and surface temperature cooling through the principal causal pathways of carbon sequestration and cloud formation. [ABSTRACT FROM AUTHOR]

A New Baseline Surface Radiation (NBSR) system was established at the Shangdianzi (SDZ) regional Global Atmosphere Watch (GAW) station in 2013 to observe nine broadband radiation components, i.e., the global-, direct-, diffuse-, and upwelling-shortwave irradiance (GSWI, DSWI, DifSWI, and UpSWI) as well as the photosynthetically active radiation (PAR), ultraviolet irradiance (UVAI; UVBI), down- and up-welling long-wave irradiance (DnLWI; UpLWI). To test the 1-min raw radiometric data, a Hybrid Algorithm for Radiation Data Quality Control (HARDQC) is presented in this study based on well-established methods together with the solar irradiance dataset and the spectral features of the instrument bands. Subsequently, an NBSR dataset, which consists of multi-time scale (i.e. 1-min, hourly, daily, monthly, monthly average hourly, and monthly average daily) radiation datasets over 2013-2022, is established and evaluated. Results show that more than 98.7% of all radiation components passed the physical possibility test. The percentages passed the extremely rare test are greater than 98.6% for all radiation components except for the DnLWI (97.1%). The percentages passed the comparison test are greater than 83.3% (GSWI), 78.3% (DSWI), 81.7% (DifSWI), 93.1% (UpSWI), 88.9% (PARI), 95.6% (UVAI), 96.3% (UVBI), 99.8% (DnLWI), and 99.7% (UpLWI), respectively. Due to data logger faults, removal of the instruments for calibration, and lightning strokes, some apparent data gaps in the upwelling radiation components (January 2015-August 2017) and all radiation components (December 2018; July to September 2021) were detected. Despite the existence of a few imperfections in the NBSR dataset, it is still reliable to apply in many fields such as the validation of satellite products and numerical models, investigation of relationships between radiation and atmospheric composition, and the detection of changes in the surface fluxes. [ABSTRACT FROM AUTHOR]

Surface solar radiation (SSR) is an essential factor in the flow of surface energy, enabling accurate capturing of long-term climate change and understanding of the energy balance of Earth's atmosphere system. However, the long-term trend estimation of SSR is subject to significant uncertainties due to the temporal inhomogeneity and the uneven spatial distribution of in situ observations. This paper develops an observational integrated and homogenized global terrestrial (except for Antarctica) station SSR dataset (SSRIH station) by integrating all available SSR observations, including the existing homogenized SSR results. The series is then interpolated in order to obtain a 5 ∘ × 5 ∘ resolution gridded dataset (SSRIH grid). On this basis, we further reconstruct a long-term (1955–2018) global land (except for Antarctica) SSR anomaly dataset with a 5 ∘ × 2.5 ∘ resolution (SSRIH 20CR) by training improved partial convolutional neural network deep-learning methods based on 20th Century Reanalysis version 3 (20CRv3). Based on this, we analysed the global land- (except for Antarctica) and regional-scale SSR trends and spatiotemporal variations. The reconstruction results reflect the distribution of SSR anomalies and have high reliability in filling and reconstructing the missing values. At the global land (except for Antarctica) scale, the decreasing trend of the SSRIH 20CR (- 1.276 ± 0.205 W m -2 per decade) is smaller than the trend of the SSRIH grid (- 1.776 ± 0.230 W m -2 per decade) from 1955 to 1991. The trend of the SSRIH 20CR (0.697 ± 0.359 W m -2 per decade) from 1991 to 2018 is also marginally lower than that of the SSRIH grid (0.851 ± 0.410 W m -2 per decade). At the regional scale, the difference between the SSRIH 20CR and SSRIH grid is more significant in years and areas with insufficient coverage. Asia, Africa, Europe and North America cause the global dimming of the SSRIH 20CR , while Europe and North America drive the global brightening of the SSRIH 20CR. Spatial sampling inadequacies have largely contributed to a bias in the long-term variation of global and regional SSR. This paper's homogenized gridded dataset and the Artificial Intelligence reconstruction gridded dataset (Jiao and Li, 2023) are both available at 10.6084/m9.figshare.21625079.v1. [ABSTRACT FROM AUTHOR]

In this study, an assessment of the FORTH radiative transfer model (RTM) surface solar radiation (SSR) as well as its interdecadal changes (Δ(SSR)), namely global dimming and brightening (GDB), is performed during the 35-year period of 1984–2018. Furthermore, a thorough evaluation of SSR and (Δ(SSR)) is conducted against high-quality reference surface measurements from 1193 Global Energy Balance Archive (GEBA) and 66 Baseline Surface Radiation Network (BSRN) stations. For the first time, the FORTH-RTM Δ(SSR) was evaluated over an extended period of 35 years and with a spatial resolution of 0.5° × 0.625°. The RTM uses state-of-the-art input products such as MERRA-2 and ISCCP-H and computes 35-year-long monthly SSR and GDB, which are compared to a comprehensive dataset of reference measurements from GEBA and BSRN. Overall, the FORTH-RTM deseasonalized SSR anomalies correlate satisfactorily with either GEBA (R equal to 0.72) or BSRN (R equal to 0.80). The percentage of agreement between the sign of computed GEBA and FORTH-RTM Δ(SSR) is equal to 63.5% and the corresponding percentage for FORTH-RTM and BSRN is 54.5%. The obtained results indicate that a considerable and statistically significant increase in SSR (Brightening) took place over Europe, Mexico, Brazil, Argentina, Central and NW African areas, and some parts of the tropical oceans from the early 1980s to the late 2010s. On the other hand, during the same 35-year period, a strong and statistically significant decrease in SSR (Dimming) occurred over the western Tropical Pacific, India, Australia, Southern East China, Northern South America, and some parts of oceans. A statistically significant dimming at the 95% confidence level, equal to −0.063 Wm−2 year−1 (or −2.22 Wm−2) from 1984 to 2018 is found over the entire globe, which was more prevalent over oceanic than over continental regions (−0.07 Wm−2 year−1 and −0.03 Wm−2 year−1, statistically significant dimming at the 95% confidence level, respectively) in both hemispheres. Yet, this overall 35-year dimming arose from alternating decadal-scale changes, consisting of dimming during 1984–1989, brightening in the 1990s, turning into dimming over 2000–2009, and brightening during 2010–2018. [ABSTRACT FROM AUTHOR]

The parameterization of deep convection is one of the primary sources of uncertainties in regional climate simulations. Due to computational constraints, long-term kilometer-scale simulations with explicit deep convection have been limited, especially over East Asia. We here conduct a pair of 10-years (2001–2010) reference simulations, one convection-parameterizing simulation at 12 km (0.11 ∘ ) resolution covering the CORDEX East Asia domain, and one 4.4-km (0.04 ∘ ) convection-permitting simulation over a subdomain. The two simulations are driven by the ERA5 reanalysis and the coarser-resolution simulation, respectively. The 4.4-km convection-permitting simulation noticeably improves the representation of the top-of-atmosphere outgoing longwave and shortwave radiation as well as precipitation intensity. In addition, sensitivity simulations are performed with perturbed sulfate and black carbon aerosols, considering the direct and semi-direct aerosol radiative effects. For the simulations with sulfate aerosol perturbations, the cloud radiative effect partly offsets the aerosol radiative effects. Decreasing sulfate aerosols leads to low-level warming, destabilizing the atmospheric stratification and thereby increasing mean precipitation and the frequency of wet days. Increasing sulfate aerosols leads to an approximately opposite response. For the simulations with black carbon aerosol perturbations, there is some near-surface warming for both increases and decreases in aerosol concentration. Also, there are significant changes in cloud cover, but changes in precipitation are comparatively weak. While for sulfate aerosol perturbations the response is approximately linear (in the sense that positive and negative perturbations yield approximately opposite effects), the response to black carbon aerosol perturbations is more complex and shows some nonlinearity, regardless of the treatment of deep convection in the simulations. We present a simple interpretation for this surprising result. [ABSTRACT FROM AUTHOR]

Decadal‐scale unforced climate variability associated with low‐frequency ocean (or coupled) modes can be identified within the time‐evolving sea surface temperature (SST) pattern. We seek to find a relationship between 12 well‐known climate modes of variability (El Niño–Southern Oscillation, Pacific Decadal Oscillation, Atlantic Multidecadal Oscillation, etc.), which are reflected in the SST pattern, and decadal trends in downwelling shortwave radiation at Earth's surface (surface solar radiation, surface shortwave radiation [SSR]). The analysis is performed using the pre‐industrial control runs (piControl) of 57 models from the Coupled Model Intercomparison Project—Phase 6. We find that regional SSR trends occur during periods when a climate mode is transitioning and show a mirroring pattern (opposite sign SSR trends) when the mode transitions in the opposite direction. Unforced trends in clear‐sky SSR are mostly driven by SST‐induced water vapor changes, while all‐sky SSR trends show a complex spatial structure with trends of different signs in different regions. Unforced SSR trends are generally weaker in simulations with climatological SSTs. The role of natural aerosols as another potentially relevant factor for SSR variability is briefly addressed and we find that constantly higher aerosol loads result in increased variability for clear‐sky conditions, but not for all‐sky conditions. The results from this study suggest that all‐sky dimming and brightening in different parts of the world are enhanced rather than suppressed by internal variability related to an SST‐pattern with the exception of India and China, where both effects are present. A practical application can be the planning of photovoltaic energy facilities given areas where internal variability is generally smaller or affects SSR in opposite directions. Plain Language Summary: The Earth system (atmosphere, ocean, land, cryosphere, and biosphere) changes not only as a result of anthropogenic or volcanic activities but also as a result of internal processes, also known as background noise. Climate science offers a simplified description of this "noise" by assigning climate indices, which help to describe the larger system with a single time series. More generally, the climate indices are an attempt to describe the temporal evolution of complex modes of variability such as El Niño–Southern Oscillation, Pacific Decadal Oscillation, and Atlantic Multidecadal Oscillation. With the use of climate models, we check how these indices are reflected in the decadal changes of solar radiation reaching Earth's surface, a flux which is mainly affected by clouds, water vapor, and natural and anthropogenic aerosols suspended in the atmosphere. Our results suggest that ocean surface temperature changes, which evolve over a few decades, control cloudiness and water vapor amounts above many land regions. This ocean temperature evolution may result in a naturally induced dimming and brightening of solar radiation over continents. Our findings are relevant for questions involving long‐term changes of the solar radiation reaching the Earth's surface, ranging from physical causes of observed changes to long term planning of photovoltaic energy production. Key Points: Long term trends in annual mean all‐sky and clear‐sky surface solar radiation entail strong changes in major climate indicesAnnual mean surface solar radiation variability is 25%–30% greater for sea surface temperatures (SSTs) that vary in time than for climatological SSTsConstantly higher aerosol loads result in increased variability for clear‐sky conditions, but not for all‐sky conditions [ABSTRACT FROM AUTHOR]

Surface solar radiation (SSR) is an essential factor in the flow of surface energy, enabling accurate capturing of long-term climate change and understanding the energy balance of Earth's atmosphere system. However, the long-term trend estimation of SSR is subjected to significant uncertainties due to the temporal inhomogeneity and the uneven spatial distribution of the in-situ observations. This paper develops an observational integrated and homogenized global-terrestrial (except for Antarctica)) stational SSR dataset (SSRIHstation) by integrating all available SSR observations, including the existing homogenized SSR results. The series are then interpolated in order to obtain a 5°×5° resolution gridded dataset (SSRIHgrid). On this basis, we further reconstruct a long-term (1955-2018) global land (except for Antarctica) SSR anomalies dataset with a 5°×2.5° resolution (SSRIH20CR) by training improved partial convolutional neural network deep learning methods based on the reanalysis 20CRv3. Based on this, we analysed the global land (except for Antarctica)/regional scale SSR trends and spatiotemporal variations: the reconstruction results reflect the distribution of SSR anomalies and have high reliability in filling and reconstructing the missing values. At the global land (except for Antarctica) scale, the decreasing trend of the SSRIH20CR (-1.276±0.205 W/m2 per decade) is slightly smaller than the trend of the SSRIHgrid (- 1.776±0.230 W/m2 per decade) from 1955 to 1991. The trend of SSRIH20CR (0.697±0.359 W/m2 per decade) from 1991 to 2018 is also marginally lower than that of the SSRIHgrid (0.851±0.410 W/m2 per decade). At the regional scale, the difference between the SSRIH20CR and SSRIHgrid is more significant in years and areas with insufficient coverage. Asia, Africa, Europe and North America cause the global dimming of the SSRIH20CR, while Europe and North America drive the global brightening of the SSRIH20CR. Spatial sampling inadequacies have largely contributed to a bias in the long-term variation of global/regional SSR. This paper's homogenized gridded dataset and the Artificial Intelligence reconstruction gridded dataset (Jiao and Li, 2023) are all available at. [ABSTRACT FROM AUTHOR]

We examine top of atmosphere (TOA), atmospheric, and surface energy budget components of 53 CMIP6 models for the period 2000–2009 on regional scales with respect to two reference data sets: the NASA Energy and Water cycle Study (NEWS), from which we adopt the regional decomposition, and the Clouds and the Earth's Radiant Energy System (CERES) Energy Balanced and Filled (EBAF). Focusing on regional scale, CMIP6 models tend to have more energy entering or less energy leaving the climate systems at TOA over the Northern Hemisphere land, Southern Hemisphere ocean and the polar regions compared to CERES EBAF, while the contrary applies in other regions. Atmospheric net shortwave and longwave fluxes both tend to be underestimated in CMIP6 models as compared to EBAF, with substantial regional differences. Regional surface radiative fluxes as reported by NEWS and EBAF can differ substantially. Nevertheless, robust regional biases exist in CMIP6. Surface upward shortwave radiation is overestimated by 43 (81%) models over Eurasia. For almost all surface radiative flux components over the North Atlantic and Indian Ocean, there are at least 21 (40%) models which fall outside the NEWS uncertainty range. Latent heat flux is overestimated over most of the land and ocean regions while firm conclusions for sensible heat flux remain elusive due to discrepancies between different reference data sets. Compared to CMIP5, there is an overall improvement in CMIP6 on regional scale. Still, substantial deficiencies and spreads on regional scale remain, which are potentially translated into an inadequate simulation of atmospheric dynamics or hydrological cycle. Plain Language Summary: The Earth's energy budget is the principal determinant of climate on our planet and is shaped by the balance between the solar energy absorbed by the Earth and the thermal energy that leaves Earth to space. The ability of Earth System Models (ESMs) to simulate the Earth's energy budget on global scale has been widely assessed in previous studies. In the present study, their ability to simulate the energy budgets on regional scales are examined in detail and compared with reference data sets and their previous model generation. Our study finds that models tend to receive more energy or lose less energy at the top of atmosphere over Northern Hemispheric land, Southern Hemispheric ocean, and polar regions. The net energy fluxes within the atmosphere are also underestimated with substantial differences between regions. In most models, some energy fluxes at the surface of the Earth are even out of the references' uncertainty range in regions such as Eurasia, the North Atlantic, and Indian Oceans. Nevertheless, compared to their previous generation, the state‐of‐the‐art ESMs investigated in our study show an overall improvement in their regional energy budgets, but deficiencies in atmospheric dynamics and hydrological cycle on regional scales should not be neglected. Key Points: This study investigates the regional energy budgets in CMIP6 models, and compares them with reference data sets and CMIP5 modelsIn most models, some energy budget components are out of the references' uncertainty range in some regionsThe regional scale energy budgets simulated by the CMIP6 models are overall improved compared to CMIP5 [ABSTRACT FROM AUTHOR]

As Earth's primary energy source, surface downward solar radiation (R s) determines the solar power potential and usage for climate change mitigation. Future projections of R s based on climate models have large uncertainties that interfere with the efficient deployment of solar energy to achieve China's carbon-neutrality goal. Here we assess 24 models in the latest Coupled Model Intercomparison Project Phase 6 with historical observations in China and find systematic biases in simulating historical R s values likely due to model biases in cloud cover and clear-sky radiation, resulting in largely uncertain projections for future changes in R s. Based on emergent constraints, we obtain credible R s with narrowed uncertainties by ∼56% in the mid-twenty-first century and show that the mean R s change during 2050–2069 relative to 1995–2014 is 30% more brightening than the raw projections. Particularly in North China and Southeast China with higher power demand, the constrained projections present more significant brightening, highlighting the importance of considering the spatial changes in future Rs when locating new solar energy infrastructures. [ABSTRACT FROM AUTHOR]

With high emissions of aerosols and the known world's "Third Pole" of the Tibet Plateau (TP) in East Asia, knowledge on the energy budget over this region has been widely concerned. This study first attempts to estimate the present-day land energy balance over East Asia by combining surface and satellite observations as well as the atmospheric reanalysis and Coupled Model Intercomparison Project Phase 6 (CMIP6) simulations. Compared to the global land budget, a substantially larger fraction of atmospheric shortwave radiation of 5.2 % is reflected, highly associated with the higher aerosol loadings and more clouds over East Asian land. While a slightly smaller fraction of atmospheric shortwave absorption of 0.6 % is unexpectedly estimated, possibly related to the lower water vapor content effects due to the thinner air over the TP to overcompensate for the aerosol and cloud effects over East Asian land. The weaker greenhouse effect and fewer low clouds due to the TP are very likely the causes of the smaller fraction of East Asian land surface downward longwave radiation. Hence, high aerosol loadings, clouds, and the TP over East Asia play vital roles in the shortwave budgets, while the TP is responsible for the longwave budgets during this regional energy budget assessment. The further obtained cloud radiative effects suggest that the presence of clouds results in a larger cooling effect on the climate system over East Asian land than that over the globe. This study provides a perspective to understand fully the roles of potential factors in influencing the different energy budget assessments over regions. [ABSTRACT FROM AUTHOR]

Quantifying future changes in solar photovoltaic (PV) potential is of great significance for energy planning and policy making to achieve carbon neutrality. To constrain the uncertainties of applying directly Coupled Model Intercomparison Project Phase 6 (CMIP6) projections to such quantification, we construct the performance‐weighted CMIP6 solar irradiance and air temperature data, and then assess the future changes in China's PV potential and accompanying economic benefits under three typical climate change scenarios. We find that the high emission scenario will substantially damage China's PV potential, resulting in a reduction of 314 TWh/year in electricity generation by the planned installed capacity in 2100, with a corresponding loss of US $25 billion/year. However, the low emission scenario will enhance the PV potential, yielding an additional electricity generation of 226 TWh/year and a corresponding bonus of US $18 billion/year in 2100. China's commitment to carbon neutrality will lead to low‐carbon emissions, which brings great economic rewards to its PV industry. Plain Language Summary: Quantifying the impact of climate change on future solar photovoltaic (PV) potential is important for energy planning and policy development in the context of the carbon neutrality. However, directly applying Coupled Model Intercomparison Project Phase 6 (CMIP6) projections to this quantification leads to large uncertainties. To this end, we reconstruct the future solar irradiance and air temperature data by weighting the CMIP6 projections according to their performance in reproducing the historical changes. Afterward, we assess the future changes in China's PV potential and the associated economic impacts under three typical climate change scenarios. We find that China's PV potential would significantly decrease under high emissions scenario, equal to an electricity generation of 314 TWh/year at planned installed capacity in 2100 and economic loss of about $25 billion/year. In contrast, PV potential would increase under low emission scenario, resulting in an additional electricity of 226 TWh/year and economic benefits of $18 billion/year. China is striving to achieve low emission development with the carbon neutrality commitment, from which the Chinese PV industry will reap huge economic rewards. Key Points: Synthesis of Coupled Model Intercomparison Project Phase 6 projections by Bayesian linear regression reduces the uncertainties of solar irradiance and air temperatureChina's future capacity factor will continuously decrease (increase) to about 0.141 (0.152) by 2100 under high (low) emission scenarioHigh emissions will result in a reduction of 314 TWh/year in electricity generation, with a corresponding loss of US $25 billion/year [ABSTRACT FROM AUTHOR]

This study assesses and evaluates the 40-year (1980–2019) Modern-Era Retrospective Analysis for Research and Applications v.2 (MERRA-2) surface solar radiation (SSR) as well as its interdecadal changes (Δ(SSR)) against high quality reference surface measurements from 1397 Global Energy Balance Archive (GEBA) and 73 Baseline Surface Radiation Network (BSRN) stations. The study is innovative since MERRA-2 (Δ(SSR)) has never been evaluated in the past, while the MERRA-2 SSR fluxes themselves have not been evaluated in such large spatial scale, which is global here, and temporal basis, which counts 40-years. Other novelties of the study are the use of the highest quality BSRN stations, done for the first time in such an evaluation, as well as the use of a greater number of reference-GEBA stations than in other studies. Moreover, the assessment and evaluation in this study are largely based on SSR anomalies, while being done in depth, at spatial scales ranging from the local to global/hemispherical, and separately for land and ocean areas, and at temporal scales spanning intervals from decadal sub-periods to 40 years. Overall, the MERRA-2 deseasonalized SSR anomalies correlate well with either GEBA (R equal to 0.61) and BSRN (R equal to 0.62). The percentage of agreement between the sign of computed GEBA and MERRA-2 Δ(SSR) is equal to 63.4% and the corresponding percentage for MERRA-2 and BSRN is 50%. According to MERRA-2, strong and statistically significant positive Δ(SSR) (Brightening) is found over Europe, Central Africa, Mongolia, Mexico, Brazil, Argentina and some parts of the tropical oceans. In contrast, large and statistically significant negative Δ(SSR) (Dimming) occurs over the western Tropical Warm Pool, India, Southern East China, Amazonia, stratocumulus covered areas and some parts of oceans. MERRA-2 yields a dimming equal to −0.158 ± 0.005 W/m2/year over the globe from 1980 to 2019. This 40-year dimming, which occurred in both hemispheres, more over ocean than continental areas (−0.195 ± 0.006 and −0.064 ± 0.006 W/m2/year, respectively), underwent decadal scale variations. [ABSTRACT FROM AUTHOR]

Anthropogenic aerosols exert a cooling influence that offsets part of the greenhouse gas warming. Due to their short tropospheric lifetime of only several days, the aerosol forcing responds quickly to emissions. Here, we present and discuss the evolution of the aerosol forcing since 2000. There are multiple lines of evidence that allow us to robustly conclude that the anthropogenic aerosol effective radiative forcing (ERF) – both aerosol–radiation interactions (ERFari) and aerosol–cloud interactions (ERFaci) – has become less negative globally, i.e. the trend in aerosol effective radiative forcing changed sign from negative to positive. Bottom-up inventories show that anthropogenic primary aerosol and aerosol precursor emissions declined in most regions of the world; observations related to aerosol burden show declining trends, in particular of the fine-mode particles that make up most of the anthropogenic aerosols; satellite retrievals of cloud droplet numbers show trends in regions with aerosol declines that are consistent with these in sign, as do observations of top-of-atmosphere radiation. Climate model results, including a revised set that is constrained by observations of the ocean heat content evolution show a consistent sign and magnitude for a positive forcing relative to the year 2000 due to reduced aerosol effects. This reduction leads to an acceleration of the forcing of climate change, i.e. an increase in forcing by 0.1 to 0.3 W m -2 , up to 12 % of the total climate forcing in 2019 compared to 1750 according to the Intergovernmental Panel on Climate Change (IPCC). [ABSTRACT FROM AUTHOR]

Solar radiation received at the Earth's surface (Rs) is comprised of two components, the direct radiation (Rd) and the diffuse radiation (Rf). Rd, the direct beam from the sun, is essential for concentrated solar power generation. Rf, scattered by atmospheric molecules, aerosols, or cloud droplets, has a fertilization effect on plant photosynthesis. But how Rd and Rf change diurnally is largely unknown owing to the lack of long‐term measurements. Taking advantage of 22 years of homogeneous hourly surface observations over China, this study documents the climatological means and evolutions in the diurnal cycles of Rd and Rf since 1993, with an emphasis on their implications for solar power and agricultural production. Over the solar energy resource region, we observe a loss of Rd which is relatively large near sunrise and sunset at low solar elevation angles when the sunrays pass through the atmosphere on a longer pathway. However, the concentrated Rd energy covering an average 10‐hr period around noon during a day is relatively unaffected. Over the agricultural crop resource region, the large amounts of clouds and aerosols scattering more of the incoming light result in Rf taking the main proportion of Rs during the whole day. Rf resources and their fertilization effect in the main crop region of China further enhances since 1993 over almost all hours of the day. Key Points: The loss of direct radiation over China since 1993 is relatively large at sunrise and sunset with little effect on solar power generationThe diffuse component dominates solar radiation normally near sunrise and sunset, but for the whole day over the main sown area of ChinaThe diffuse fraction is further enhanced in the main sown area of China over almost all hours of the day since 1993 [ABSTRACT FROM AUTHOR]

Time series of clear‐sky irradiance are fundamental for the understanding of changes in the Earth Radiation budget, since they allow to examine radiative processes in the cloud‐free atmosphere. Clear‐sky data is usually derived from all‐sky irradiances using one of several clear‐sky methods proposed in the literature. However, most of the available clear‐sky methods require additional in situ measurements and/or high temporal resolution (sub‐daily), which restricts the derivation of clear‐sky time series to a few well equipped stations. Here we propose a new clear‐sky identification method that aims to overcome this problem, with the ultimate goal of deriving multidecadal clear‐sky trends for many sites globally. The method uses site specific monthly transmittance thresholds to derive long term clear‐sky time series for any station worldwide that has daily mean irradiance data. We exemplify the method for 24 stations. Transmittance thresholds are derived by combining 29 years (1990–2018) of satellite cloud cover data with in situ irradiance measurements. The thresholds are then applied to the whole time series (independent of satellite data availability) to screen out cloudy days. Comparison of our results with reference data derived using Long and Ackerman's (2000, https://doi.org/10.1029/2000jd900077) method shows good agreement after bias correction, especially for decadal trends. While limitations of the method, such as anomalies representation, are highlighted and discussed, validation results encourage its use to derive long term clear‐sky time series and associated decadal‐scale trends around the globe. Key Points: A clear‐sky detection method using only daily mean surface solar radiation is proposed and validated, with focus on decadal scale trendsMethod calibration requires in addition satellite cloud fraction data, to derive site and calendar month specific transmittance thresholdsMethod validation for 24 sites suggests its usefulness for deriving long term clear‐sky trends worldwide, albeit with slight bias [ABSTRACT FROM AUTHOR]

Renewable generation variability over multiple days is a key challenge in decarbonizing the European power system. Weather regimes are one way to quantify this variability, but so far, their applications to energy research have focused on wind power generation in winter. However, the projected growth of solar photovoltaic (PV) capacity implies that its absolute variability across the continent will grow substantially. Here we combine weather regimes based on ERA5 reanalysis data with country‐specific capacity factors to investigate multiday PV generation variability in Europe. With current installed capacity (131 GW), total PV production in Europe (52.3 GW) varies by 0.9 GW on average, with a maximum change of 3.0 GW, upon transition from one weather regime to another. Using projected PV capacity for 2050 (1.94 TW), variability would rise to 13.9 and 43.8 GW. We present optimized spatial distributions of capacity additions in three scenarios that substantially reduce variability by up to 40%. One of them ascertains a large local PV production, thereby minimizing the need for long‐range power transmission while still reducing variability by about 30%, highlighting that optimized siting and local generation can be reconciled. Our results emphasize the value of leveraging climate information in decarbonizing power systems. Key Points: Year‐round weather regime classification with linked photovoltaic (PV) capacity factors per country in EuropeEuropean multiday PV variability could be as high as 43.8 GW in 2050Optimized distribution of PV systems in Europe reduces multiday variability up to 40% [ABSTRACT FROM AUTHOR]

Internal variability comprises all processes that occur within the climate system without any natural or anthropogenic forcing. Climate‐driving variables like the surface solar radiation (SSR) are shown to exhibit unforced trends (i.e., trends due to internal variability) of magnitudes comparable to the magnitude of the forced signal even on decadal timescales. We use annual mean data from 50 models participating in the preindustrial control experiment (piControl) of the Coupled Model Intercomparison Project‐Phase 6 (CMIP6) to give quantitative grid‐box specific estimates of the magnitudes of unforced trends. To characterize a trend distribution, symmetrical around 0, we use the 75th percentile of all possible values, which corresponds to a positive trend with 25% chance of occurrence. For 30‐year periods and depending on geographical location, this trend has a magnitude between 0.15 and 2.1 W m−2/decade for all‐sky and between 0.04 and 0.38 W m−2/decade for clear‐sky SSR. The corresponding area‐weighted medians are 0.69 W m−2/decade for all‐sky trends and 0.17 W m−2/decade for clear‐sky trends. The influence of internal variability is on average six times smaller in clear‐sky, compared to all‐sky SSR. The relative uncertainties in the physical representation, derived from the CMIP6 inter‐model spread, are ±32% for all‐sky and ±43% for clear‐sky SSR trends. Reasons for differences between models like horizontal resolution, aerosol handling, and the representation of atmospheric and oceanic phenomena are investigated. The results can be used in the analysis of observational time series by attributing a probability for a trend to be caused by internal variability, given its magnitude, length, and location. Key Points: Internal variability of all‐sky and clear‐sky SSR and associated decadal‐scale unforced trends are quantified probabilisticallyClouds contribute to a larger fraction of unforced trends: internal variability is ∼6 times smaller in clear‐sky as compared to all‐sky SSRUnforced SSR trends are particularly strong in some regions, the regional pattern being different for clear‐sky and all‐sky trends [ABSTRACT FROM AUTHOR]

With high emissions of aerosols and the known world's "Third Pole" of the Tibet Plateau (TP) in East Asia, knowledge on the energy budget over this region is widely concerned. This study first attempts to estimate the present-day land energy balance over East Asia by combining surface and satellite observations, as well as the atmospheric reanalysis and Coupled Model Intercomparison Project phase 6 (CMIP6) simulations. Compared to the global land budget, a substantially larger fraction of atmospheric shortwave radiation of 5.2% is reflected, highly associated with the higher aerosol loadings and more clouds over East Asian land. While a slightly smaller fraction of atmospheric shortwave absorption of 0.6% is unexpectedly estimated, possibly related to the lower water vapor content effects due to the thinner air over the TP to overcompensate for the aerosol and cloud effects over East Asian land. The weaker greenhouse effect and fewer low clouds due to the TP are very likely the causes for the smaller fraction of East Asian31 land surface downward longwave radiation. Hence, high aerosol loadings, clouds, and the TP over East Asia play vital roles in the shortwave budgets, while the TP is responsible for the longwave budgets during this regional energy budget assessment. The further obtained cloud radiative effects suggest that the presence of clouds results in a larger cooling effect on the climate system over East Asian land than that over globe. This study helps understand the potential factors influencing the diversifying energy budget assessments over regions. [ABSTRACT FROM AUTHOR]

Anthropogenic aerosols exert a cooling influence that offsets part of the greenhouse gas warming. Due to their short tropospheric lifetime of only up to several days, the aerosol forcing responds quickly to emissions. Here we present and discuss the evolution of the aerosol forcing since 2000. There are multiple lines of evidence that allow to robustly conclude that the anthropogenic aerosol effective radiative forcing - both aerosol-radiation and aerosol-cloud interactions - has become globally less negative, i.e. that the trend in aerosol effective radiative forcing changed sign from negative to positive. Bottom-up inventories show that anthropogenic primary aerosol and aerosol precursor emissions declined in most regions of the world; observations related to aerosol burden show declining trends, in particular of the fine-mode particles that make up most of the anthropogenic aerosols; satellite retrievals of cloud droplet numbers show trends consistent in sign, as do observations of top-of-atmosphere radiation. Climate model results, including a revised set that is constrained by observations of the ocean heat content evolution show a consistent sign and magnitude for a positive forcing relative to 2000 due to reduced aerosol effects. This reduction leads to an acceleration of the forcing of climate change, i.e. an increase in forcing by 0.1 to 0.3Wm-2, up to 12% of the total climate forcing in 2019 compared to 1750 according to IPCC. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "Aerosol sensitivity simulations over East Asia in a convection-permitting climate model" published in Climate Dynamics. The correction addresses an error in Figure 8 of the original article and provides the correct version of the figure. The corrected article has been published and the publisher, Springer Nature, remains neutral regarding jurisdictional claims and institutional affiliations. The authors of the article are Shuping Li, Silje Lund Sørland, Martin Wild, and Christoph Schär. [Extracted from the article]

Downward surface solar radiation (SSR) is a crucial component of the global energy balance, affecting temperature and the hydrological cycle profoundly, and it provides crucial information about climate change. Many studies have examined SSR trends; however, they have often concentrated on specific regions due to limited spatial coverage of ground-based observation stations. To overcome this spatial limitation, this study performs a spatial interpolation based on a machine learning method, random forest, to interpolate monthly SSR anomalies using a number of climatic variables (various temperature indices, cloud coverage, etc.), time-point indicators (years and months of SSR observations), and geographical characteristics of locations (latitude, longitude, etc.). The predictors that provide the largest explanatory power for interannual variability are diurnal temperature range and cloud coverage. The output of the spatial interpolation is a 0.5° × 0.5° monthly gridded dataset of SSR anomalies with complete land coverage over the period 1961–2019, which is used afterward in a comprehensive trend analysis for (i) each continent separately and (ii) the entire globe. The continental-level analysis reveals the major contributors to the global dimming and brightening. In particular, the global dimming before the 1980s is primarily dominated by negative trends in Asia and North America, whereas Europe and Oceania have been the two largest contributors to the brightening after 1982 and up until 2019. [ABSTRACT FROM AUTHOR]

Selumetinib (ARRY‐142886), an oral, potent and highly selective allosteric mitogen‐activated protein kinase kinase 1/2 inhibitor, is approved by the US Food and Drug Administration for the treatment of pediatric patients aged ≥2 years with neurofibromatosis type 1 with symptomatic, inoperable plexiform neurofibromas. A physiologically based pharmacokinetic (PBPK) model was constructed to predict plasma concentration–time profiles of selumetinib, and to evaluate the impact of coadministering moderate cytochrome P450 (CYP) 3A4/2C19 inhibitors/inducers. The model was also used to extrapolate pharmacokinetic exposures from older children with different body surface area to guide dosing in younger children. This model was built based on physiochemical data and clinical in vivo drug‐drug interaction (DDI) studies with itraconazole and fluconazole, and verified against data from an in vivo rifampicin DDI study and an absolute bioavailability study. The pediatric model was updated by changing system‐specific input parameters using the Simcyp pediatric module. The model captured the observed selumetinib pharmacokinetic profiles and the interactions with CYP inhibitors/inducers. The predictions from the PBPK model showed a DDI effect of 30% to 40% increase or decrease in selumetinib exposure when coadministered with moderate CYP inhibitors or inducers, respectively, which was used to inform dose management and adjustments. The pediatric PBPK model was applied to simulate exposures in specific body surface area brackets that matched those achieved with a 25 mg/m2 dose in SPRINT clinical trials. The pediatric PBPK model was used to guide the dose for younger patients in a planned pediatric clinical study. [ABSTRACT FROM AUTHOR]

Solar photovoltaics (PV) plays an essential role in decarbonizing the European energy system. However, climate change affects surface solar radiation and will therefore directly influence future PV power generation. We use scenarios from Phase 6 of the Coupled Model Intercomparison Project (CMIP6) for a mitigation (SSP1-2.6) and a fossil-fuel-dependent (SSP5-8.5) pathway in order to quantify climate risk for solar PV in Europe as simulated by the Global Solar Energy Estimator (GSEE). We find that PV potential increases by around 5 % in the mitigation scenario, suggesting a positive feedback loop between climate change mitigation and PV potential. While increased clear-sky radiation and reduced cloud cover go hand in hand in SSP1-2.6, the effect of a decrease in clear-sky radiation is outweighed by a decrease in cloud cover in SSP5-8.5, resulting in an increase in all-sky radiation. Moreover, we find that the seasonal cycle of PV generation changes in most places, as generation grows more strongly in winter than in summer (SSP1-2.6) or increases in summer and declines in winter (SSP5-8.5). We further analyze climate change impacts on the spatial variability of PV power generation. Similar to the effects anticipated for wind energy, we report an increase in the spatial correlations of daily PV production with large inter-model agreement yet relatively small amplitude, implying that PV power balancing between different regions in continental Europe will become more difficult in the future. Thus, based on the most recent climate simulations, this research supports the notion that climate change will only marginally impact renewable energy potential, while changes in the spatiotemporal generation structure are to be expected and should be included in power system design. [ABSTRACT FROM AUTHOR]

Ionic liquids are considered as tunable designer liquids that may provide the perfect environment or active species for chemical reactions. N-Heterocyclic carbenes are known to be important organocatalysts enabling novel and specific routes for general synthetic strategies. There has been a lot of speculation about the role, stability, and the existence of in situ formed carbenes in ionic liquids. Here, we show that cation stabilised carbenes can exist in room temperature ionic liquids as reactive intermediates detectable with liquid microbeam IR laser desorption mass spectrometry. The experimental results were supported by density functional theory. Intriguingly, we also found that carbenes appear to correlate with and may be the origin of strong chemisorption of carbon dioxide in ionic liquids. [ABSTRACT FROM AUTHOR]

Solar photovoltaics (PV) plays an essential role in decarbonizing the European energy system. However, climate change affects surface solar radiation and thereby will directly influence future PV power generation. We use scenarios from the sixth phase of the Coupled Model Intercomparison Project (CMIP6) for a mitigation (SSP1-2.6) and a fossil-fuel dependent (SSP5-8.5) pathway, to quantify climate risk for solar PV in Europe simulated by the Global Solar Energy Estimator (GSEE). We find that PV potential increases by around 5 % in the mitigation scenario, suggesting a positive feedback loop between climate change mitigation and PV potential. While increased clear-sky radiation and reduced cloud cover go hand in hand in SSP1-2.6, a decrease in clear-sky radiation is overcompensated by a decrease in cloud cover in SSP5-8.5, resulting in an increase of all-sky radiation. Moreover, we find that the seasonal cycle of PV generation changes in most places as generation grows more strongly in winter than in summer (SSP1-2.6) or increases in summer and declines in winter (SSP5-8.5). We further analyze climate change impacts on the spatial variability of PV power generation. Similar to effects anticipated for wind energy, we report an increase of the spatial correlations of daily PV production with large inter-model agreement yet relatively small amplitude, implying that PV power balancing between different regions in continental Europe will become more difficult in the future. Based on the most recent climate simulations, this research thus supports the notion that climate change will only marginally impact renewable energy potential, while changes in the spatio-temporal generation structure are to be expected and should be included in power system design. [ABSTRACT FROM AUTHOR]

Terrain reflected solar radiation in snow‐covered mountains is nonnegligible in investigations of the energy budget. However, it has so far not been investigated thoroughly, especially with regard to the influence of snow cover. Several parameterization approaches have been raised but not yet evaluated in a more uniform and quantitative manner. Based on the three‐dimensional (3‐D) ray‐tracing simulation, we explored the temporal and spatial characteristics of the terrain reflected radiation in 15 domains on the southeastern Tibetan Plateau, and comprehensively evaluated different parameterization approaches. The results indicate that the ratio of reflected radiation to total daily radiation ranges from 0.25% to 10.85% at the scale of 5 × 5 km2 in a winter clear day, and it is 57% higher at noon in spring and autumn due to the higher snow cover fraction. Snow cover not only enhances the magnitude of reflected radiation by increasing surface albedo but also changes the spatial distribution pattern of radiation in partial snow‐covered mountains, causing more snow‐reflected radiation to be received by the surrounding surfaces. Three forms of terrain configuration factors in common parameterization approaches were evaluated by the ray‐tracing model. The complementary of sky view factor shows good consistency with ray‐tracing model at domain‐averaged scales, with a root mean square error (RMSE) of 2.55 (14%) W/m2, while the other two both underestimate the radiation. The parameterization approach involving the multi‐reflection shows better performance with the normalized RMSE decreasing by 5%. However, the uncertainty of it increases with the surface spatial heterogeneity caused by the partial snow cover, especially at high resolution. Key Points: A ray‐tracing model was used to investigate terrain reflected solar radiation in snow‐covered high mountainsPartial snow cover leads to more incident reflected radiation on snow‐covered slopes in spatial distributionPerformance of different parameterization approaches was evaluated in detail [ABSTRACT FROM AUTHOR]

A total of 56 years (1961–2016) of daily surface downward solar irradiation, sunshine duration, diurnal temperature range and the fraction of the sky covered by clouds in the city of São Paulo, Brazil, were analysed. The main purpose was to contribute to the characterization and understanding of the dimming and brightening effects on solar global radiation in this part of South America. As observed in most of the previous studies worldwide, in this study, during the period between 1961 and the early 1980s, a negative trend in surface solar irradiation was detected in São Paulo, characterizing the occurrence of a dimming effect. Sunshine duration and the diurnal temperature range also presented negative trends, in opposition to the positive trend observed in the cloud cover fraction. However, a brightening effect, as observed in western industrialized countries in more recent years, was not observed. Instead, for surface downward irradiation, the negative trend persisted, with a trend of -0.13 MJ m -2 per decade, with a p value of 0.006, for the 56 years of data and in consonance with the cloud cover fraction increasing trend, but not statistically significant, of 0.3 % per decade (p value = 0.198). The trends for sunshine duration and the diurnal temperature range, by contrast, changed signal, as confirmed by a piecewise linear regression model. Some possible causes for the discrepancy are discussed, such as the frequency of fog occurrence, urban heat island effects, horizontal visibility (as a proxy for aerosol loading variability) and greenhouse gas concentration increase. Future studies on the aerosol effect are planned, particularly with higher temporal resolution, as well as modelling studies, to better analyse the contribution of each possible cause. [ABSTRACT FROM AUTHOR]

For the explanation of the observed decadal variations in surface solar radiation (known as dimming and brightening), the relative importance of clouds and the cloud‐free atmosphere (particularly aerosols) is currently disputed. Here, we investigate this issue using daily data from the prominent long‐term observational radiation record at Potsdam, Germany, over the 71‐year period 1947–2017. We identify cloud‐free days based on synop cloud observations as well as on days with maximum atmospheric transmission. Irrespective of the cloud‐screening method, strong dimming and brightening tendencies in the atmospheric transmission are evident not only under all‐sky but also of similar magnitude under clear‐sky conditions, causing multidecadal variations in surface solar radiation on the order of 10 Wm−2. This points to the cloud‐free atmosphere as a main responsible for dimming and brightening in central Europe and suggests that these variations are anthropogenically forced rather than of natural origin, with aerosol pollutants as likely major drivers. Plain Language Summary: The amount of sunlight received at the Earth's surface undergoes substantial variations on decadal timescales, known as "dimming and brightening." These variations have fundamental implications for a variety of key environmental issues as well as for solar power generation, agriculture, and human health. However, the causes of these variations are still insufficiently established and currently disputed. Particularly debated is whether these variations are man‐made through air pollution (and associated blocking of sunlight by aerosols), or rather a result of natural variations in the climate system (through the modulation of sunlight by clouds). Here, we investigate this issue based on one of the longest and best maintained records of sunlight measured at Potsdam, Germany. We filter out the effects of clouds on solar radiation in this prominent record, to be able to study the variations in sunlight both under cloudy and cloud‐free conditions. Our analysis shows that strong decadal variations (dimming and brightening) not only appear when clouds are considered but also remain evident under cloud‐free conditions when cloud effects are eliminated. This implies that aerosol pollutants play a crucial role in these variations and points to a discernible human influence on the vital level of sunlight required for sustainable living conditions. Key Points: The Potsdam solar radiation record, one of the world's longest and best maintained measurement series, is a key witness of the dimming and brightening phenomenonFor the first time, we investigate dimming and brightening tendencies in this prominent record not only under "all‐sky" but also under "clear‐sky" conditionsDimming and brightening is evident also under cloud‐free conditions, pointing to a human influence through aerosol pollutants as major cause of these variations [ABSTRACT FROM AUTHOR]

Exploration of the diurnal pattern of global dimming and brightening has been limited by the paucity of high‐temporal resolution observations. Based on 22 years' continuous observations of hourly surface solar radiation (SSR) over 96 stations across China for 1993–2014, this study evidences higher relative changes in diurnal SSR in terms of both frequency and magnitude at sunrise and sunset, with a longer pathway for the sun passing through the atmosphere, than the hours in between. This, in general, leads to a further shortening of the days between sunrise and sunset in the cold seasons and the polluted region of north China with low radiation levels but a further extension in the other seasons and regions with sufficient sunlight. Pollution reduction by 39.4%–69.7% during the 2014 Asia‐Pacific Economic Cooperation summit at Beijing are accompanied with a 10.4–80.0% rebound of diurnal SSR in the forenoon and late afternoon. Plain Language Summary: As the primary energy source for our planet, solar radiation received at the Earth's surface, i.e., surface solar radiation (SSR), has undergone significant decadal changes. But at which specific time of the day does such change mostly occur remains a question, due to the limited SSR data at hourly or shorter timescales. Since 1993, China automated its measuring instruments and started continuous hourly SSR observations. Using these historical data records, this study evidences that the largest changes in SSR occur at the hours close to sunset and sunrise, which is also known as the early morning and late afternoon rush hours. The detected dimming and brightening of SSR at sunset and sunrise could affect the period of daytime, respectively, resulting in a further shortening of the days in cold seasons and polluted regions but a further extension in the other seasons and regions with sufficient sunlight. The emission reduction campaign directed by the Chinese government during the 2014 Asia‐Pacific Economic Cooperation (APEC) summit at Beijing has remarkably induced an increase in the diurnal cycle of SSR, especially in the forenoon and late afternoon as compared to the Pre‐APEC period, contrary to the normal changes solely driven by solar cycle. Key Points: Daytime‐dependent dimming and brightening in surface solar radiation is most clearly imprinted near sunrise and sunset over ChinaDaytime shortens in the cold seasons and polluted regions of China but further prolongs in the other seasons and regions since 1993The 2014 APEC Blue phenomenon at Beijing induced a change in the diurnal cycle of surface solar radiation [ABSTRACT FROM AUTHOR]

Anthropogenic aerosol emissions have increased considerably over the last century, but climate effects and quantification of the emissions are highly uncertain as one goes back in time. This uncertainty is partly due to a lack of observations in the pre-satellite era, making the observations we do have before 1990 additionally valuable. Aerosols suspended in the atmosphere scatter and absorb incoming solar radiation and thereby alter the Earth's surface energy balance. Previous studies show that Earth system models (ESMs) do not adequately represent surface energy fluxes over the historical era. We investigated global and regional aerosol effects over the time period 1961–2014 by looking at surface downwelling shortwave radiation (SDSR). We used observations from ground stations as well as multiple experiments from eight ESMs participating in the Coupled Model Intercomparison Project Version 6 (CMIP6). Our results show that this subset of models reproduces the observed transient SDSR well in Europe but poorly in China. We suggest that this may be attributed to missing emissions of sulfur dioxide in China, sulfur dioxide being a precursor to sulfate, which is a highly reflective aerosol and responsible for more reflective clouds. The emissions of sulfur dioxide used in the models do not show a temporal pattern that could explain observed SDSR evolution over China. The results from various aerosol emission perturbation experiments from DAMIP, RFMIP and AerChemMIP show that only simulations containing anthropogenic aerosol emissions show dimming, even if the dimming is underestimated. Simulated clear-sky and all-sky SDSR do not differ greatly, suggesting that cloud cover changes are not a dominant cause of the biased SDSR evolution in the simulations. Therefore we suggest that the discrepancy between modeled and observed SDSR evolution is partly caused by erroneous aerosol and aerosol precursor emission inventories. This is an important finding as it may help interpret whether ESMs reproduce the historical climate evolution for the right or wrong reason. [ABSTRACT FROM AUTHOR]

Fifty-six years (1961-2016) of daily surface downward solar irradiation, sunshine duration, diurnal temperature range and the fraction of the sky covered by clouds in the city of São Paulo, Brazil, were analyzed. The main purpose was to contribute to the characterization and understanding of the dimming and brightening effects on solar global radiation in this part of South America. As observed in most of the previous studies worldwide, in this study, during the period between 1961 up to the early 1980's, more specifically up to 1983, a negative trend in surface solar irradiation was detected in São Paulo, characterizing the occurrence of a dimming effect. A similar behavior, a negative trend, was also observed for sunshine duration and the diurnal temperature range, the three variables in opposition to the trend in the sky cover fraction. However, a brightening effect, as observed in western industrialized countries in more recent years, was not observed. Instead, for surface downward irradiation, the negative trend persisted and still in consonance to the cloud cover fraction increasing trend. The trends for sunshine duration and the diurnal temperature range, by contrast, changed signal. Some possible causes for the discrepancy were discussed, such as the frequency of fog occurrence, urban heat island effects, aerosol changes and greenhouse gas concentration increase. Future studies on aerosol effect are encouraged, particularly with higher temporal resolution as well as modeling studies, to better analyze the contribution of each possible causes. [ABSTRACT FROM AUTHOR]

A plausible simulation of the global energy balance is a first-order requirement for a credible climate model. Here I investigate the representation of the global energy balance in 40 state-of-the-art global climate models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6). In the CMIP6 multi-model mean, the magnitudes of the energy balance components are often in better agreement with recent reference estimates compared to earlier model generations on a global mean basis. However, the inter-model spread in the representation of many of the components remains substantial, often on the order of 10–20 Wm−2 globally, except for aspects of the shortwave clear-sky budgets, which are now more consistently simulated by the CMIP6 models. The substantial inter-model spread in the simulated global mean latent heat fluxes in the CMIP6 models, exceeding 20% (18 Wm−2), further implies also large discrepancies in their representation of the global water balance. From a historic perspective of model development over the past decades, the largest adjustments in the magnitudes of the simulated present-day global mean energy balance components occurred in the shortwave atmospheric clear-sky absorption and the surface downward longwave radiation. Both components were gradually adjusted upwards over several model generations, on the order of 10 Wm−2, to reach 73 and 344 Wm−2, respectively in the CMIP6 multi-model means. Thereby, CMIP6 has become the first model generation that largely remediates long-standing model deficiencies related to an overestimation in surface downward shortwave and compensational underestimation in downward longwave radiation in its multi-model mean. [ABSTRACT FROM AUTHOR]

In birds the auditory system plays a key role in providing the sensory input used to discriminate between conspecific and heterospecific vocal signals. In those species that are known to learn their vocalizations, for example, songbirds, it is generally considered that this ability arises and is manifest in the forebrain, although there is no a priori reason why brainstem components of the auditory system could not also play an important part. To test this assumption, we used groups of normal reared and cross-fostered zebra finches that had previously been shown in behavioural experiments to reduce their preference for conspecific songs subsequent to cross fostering experience with Bengalese finches, a related species with a distinctly different song. The question we asked, therefore, is whether this experiential change also changes the bias in favour of conspecific song displayed by auditory midbrain units of normally raised zebra finches. By recording the responses of single units in MLd to a variety of zebra finch and Bengalese finch songs in both normally reared and cross-fostered zebra finches, we provide a positive answer to this question. That is, the difference in response to conspecific and heterospecific songs seen in normal reared zebra finches is reduced following cross-fostering. In birds the virtual absence of mammalian-like cortical projections upon auditory brainstem nuclei argues against the interpretation that MLd units change, as observed in the present experiments, as a result of top-down influences on sensory processing. Instead, it appears that MLd units can be influenced significantly by sensory inputs arising directly from a change in auditory experience during development. [ABSTRACT FROM AUTHOR]

A novel method has been developed to estimate aerosol optical depth (AOD) from sunshine duration (SD) measurements under cloud-free conditions. It is a physically based method serving for the reconstruction of the historical evolution of AOD during the last century. In addition to sunshine duration data, it requires daily water vapor and ozone products as inputs taken from the ECMWF 20th century reanalysis ERA-20C, available at the global scale over the period 1900–2010. Surface synoptic cloud observations are used to identify cloud-free days. For 16 sites over Europe, the accuracy of the estimated daily AOD, and its seasonal variability, is similar to or better than those from two earlier methods when compared to AErosol RObotic NETwork measurements. In addition, it also improves the detection of the signal from massive aerosol events such as important volcanic eruptions (e.g., Arenal and Fernandina Island in 1968, El Chichón in 1982 and Pinatubo in 1992). Finally, the reconstructed AOD time series are in good agreement with the dimming/brightening phenomenon and also provide preliminary evidence of the early-brightening phenomenon. [ABSTRACT FROM AUTHOR]

Increasing energy and food demands require an understanding of not only the availability and variability of total solar radiation (R) but also its partitioning into direct (Rd) and diffuse (Rf) components, which are key elements for solar power generation and plant photosynthesis, respectively. Potential inhomogeneities in surface solar radiation observations, however, add uncertainties to the published patterns and trends of Rd and Rf over China. To exclude inhomogeneous time series and outliers, a data quality control process has been applied to the surface observations of Rd and Rf. The homogeneous data show that, in response to the global dimming and brightening phenomena in R, decadal changes can also be observed in the Rd and Rf trends over China with the actual transition occurring in the mid‐2000s. Since the 1960s, Rd dimming has mainly distributed over eastern China with intensive anthropogenic activities, with recoveries especially from 2008 onward over regions with high Rd energy potential. Rf, on the other hand, had further enhanced since the 1960s especially over the high Rf proportion areas but has decreased in the recent decade over the northern region. The summer season shows the most significant decadal trends in Rd and Rf. Under clear‐sky conditions, that is, ruling out cloud effects, the transitions in Rd and Rf trends become more remarkable, pointing to atmospheric aerosols as the main driving force. In addition, dramatic Rd and Rf variations are observed in the subsequent years after large volcanic eruptions. The varying Rd and Rf proportions are in line with recent governmental control on SO2 emissions over China. Key Points: Homogeneous observations show a recent transition to brightening in direct radiation and to dimming in diffuse radiation over China since 2008Clear‐sky trends suggest an impact of volcanic eruption on the dramatic changes in solar radiation over China during the early 1990sGovernmental control on pollutant emissions may have contributed to the variations of direct and diffuse radiation proportions over China [ABSTRACT FROM AUTHOR]