From Dimming to Brightening: Decadal Changes in Solar Radiation at Earth's Surface

Institute for Atmospheric and Climate Science, Swiss Federal Institute of Technology (ETH), Winter-thurerstrasse 190, CH-8057 Zurich, Switzerland.
Science (Impact Factor: 33.61). 06/2005; 308(5723):847-50. DOI: 10.1126/science.1103215
Source: PubMed


Variations in solar radiation incident at Earth's surface profoundly affect the human and terrestrial environment. A decline in solar radiation at land surfaces has become apparent in many observational records up to 1990, a phenomenon known as global dimming. Newly available surface observations from 1990 to the present, primarily from the Northern Hemisphere, show that the dimming did not persist into the 1990s. Instead, a widespread brightening has been observed since the late 1980s. This reversal is reconcilable with changes in cloudiness and atmospheric transmission and may substantially affect surface climate, the hydrological cycle, glaciers, and ecosystems.

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Available from: Atsumu Ohmura,
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    • "Global solar radiation is the primary energy source for life on our planet, which largely determines the climatic conditions of our habitats (Budyko 1969; Wild et al. 2009; Wang et al. 2015a, b). A decreasing global solar radiation around the world (the solar dimming phenomenon) was observed between the 1950s and 1980s (Ohmura 2009; Wild 2009), and the global solar radiation began to increase (the brightening phenomenon) since the late 1980s (Alpert et al. 2005; Wild et al. 2005, 2009). It has been reported that the global solar radiation has generally increased in Germany, Austria, Switzerland, France and United Kingdom during 1985–2005 (Wild et al. 2009). "
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    ABSTRACT: Long-term variation of estimated global solar radiation (Eg↓) and its relationship with total cloud cover (TCC), low cloud cover (LCC), water vapor content (WVC) and aerosol optical depth (AOD) were investigated based on observations at 21 meteorological stations in Hunan province, China. Long-term variations of all variables were calculated for each station, the Mann-Kendall trend test was used to detect the significant level of temporal development trend for each variable, the Pearson correlation analysis was used to measure their linear relationships. Annual Eg↓ generally decreased at the rate of -2.11×10-3 MJ m-2 decade-1 in Hunan province during 1980-2013. Seasonal mean Eg↓ decreased at the rate of -11.99×10-3, -4.71×10-3 and -4.51×10-3 MJ m-2 decade-1 in summer, autumn and winter, respectively, while the increasing trend was observed in spring (15.74×10-3 MJ m-2 decade-1). The annual variation of Eg↓ in Hunan province was dominantly determined by the variations of AOD (0.33×10-3 decade-1) and LCC (0.24% p decade-1). But the spatial variation of Eg↓ in Hunan province was complex. All 21 stations were divided into four groups according to the long-term trends of Eg↓, TCC, LCC, AOD and WVC. An increasing Eg↓ was observed at stations in group 1, which were determined by the variability of TCC. The variability of AOD and TCC might contribute to the increasing Eg↓ in group 2. There were decreasing trends of Eg↓ for the stations in group 3 and group 4, which were largely determined by the increases of AOD and LCC.
    Meteorology and Atmospheric Physics 10/2015; DOI:10.1007/s00703-015-0410-4 · 1.05 Impact Factor
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    • "This is supported by the fact that observed decadal changes in anthropogenic aerosol emissions are in line with the trends in global solar radiation (Wild, 2009; Folini and Wild, 2011). These evidences have also been supported by changes in solar radiation under clear-sky conditions (Wild et al., 2005; Norris and Wild, 2007, 2009; Ruckstuhl et al., 2008; Folini and Wild, 2011; Soni et al., 2012). Change in aerosol optical depth has been suggested to play a role in the radiation change over China (Kaiser and Qian, 2002), India (Ramanathan and Ramana, 2005; Soni et al., 2012), Europe (Norris and Wild, 2007), and other regions (Wild, 2012). "

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    • "In contrast, a brightening period was observed from the 1980s onwards (Wild et al., 2005; Sanchez-Lorenzo et al., 2013a). It should be noted, however, that such a phenomenon has nothing to do with the Sun's variability, but rather with the interactions of solar radiation primarily with aerosols and clouds as it passes through the Earth's atmosphere on its way to the surface (Stanhill and Cohen, 2001; Ohmura, 2009; Wild, 2009). "
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    ABSTRACT: For a better understanding of multidecadal climate change, as well as for the production of solar power, there is a growing need for knowledge of the trends in incident sunlight at the Earth's surface, but a lack of a long-term sunlight time series dictates that a proxy measure is needed. In this study, variations of sunshine duration and diurnal temperature range (DTR) are used as proxies for surface solar radiation. Annual and seasonal composites of both variables from 29 stations are analyzed from 1961 through 2009 across the different types of climates of Iran. The annual sunshine duration mean time series shows a decrease from the early 1960s to the late 1970s, in line with the widespread dimming of surface solar radiation observed during this period. By the early 1980s, there is an increase in sunshine through the end of the 20th century, aligning with a well-known and well-documented brightening period. In addition, a renewed dimming is observed during the 2000s, with a sharp drop in 2009. A linear trend estimated over the 1961–2009 period was not found to be statistically significant. However, the annual DTR time series shows a widespread and statistically significant decrease since the 1960s, although the series ends without relevant variations after the 1990s. An agreement in the interannual variability of sunshine and DTR is observed except for the summer season. On decadal time scales, only the spring DTR series shows a partial agreement with sunshine series. Nevertheless, the recent leveling off in the DTR series supports a transition in the radiative regime.
    International Journal of Climatology 06/2015; 35:2065–2079. DOI:10.1002/joc.4107 · 3.16 Impact Factor
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