How extremes in surface incident solar radiation shape its long-term trends in China and Europe

Abstract Although extremes of surface incident solar radiation ( R s ) are critical for climate and energy assessments, their long-term variations and contributions to R s trends remain poorly understood. Leveraging the recently homogenized daily R s data at ∼2600 stations across China and Europe during 1961–2022, this study provided the first quantification of long-term variations in extremely low ( R s 10p) and high ( R s 90p) R s and their contributions to R s trends. During the dimming period, increasing R s 10p and decreasing R s 90p frequencies, along with increased magnitudes, jointly led to the dimming over China and Europe. Europe began to steadily brighten after 1980, due to early air pollution emission controls and reduced cloud cover, which reversed the frequency trends of R s 10p and R s 90p and intensified the severities of both extremes. In contrast, dimming in China persisted until 2014, only transitioning to brightening after the implementation of stricter emission controls which increased R s 90p frequencies but attenuated the severities of both extremes. Overall, R s extremes jointly regulated R s trends: China’s brightening was positively contributed by both extremes, while Europe’s brightening was dominated by R s 90p but partially offset by R s 10p. These findings underscore the pivotal role of extremes in shaping overall R s trends and highlight their importance for accurately assessing regional solar energy availability under global climate change.