Although extremes of surface incident solar radiation (Rs) are critical for climate and energy assessments, their long-term variations and contributions to Rs trends remain poorly understood. Leveraging the recently homogenized daily Rs data at ∼2600 stations across China and Europe during 1961–2022, this study provided the first quantification of long-term variations in extremely low (Rs10p) and high (Rs90p) Rs and their contributions to Rs trends. During the dimming period, increasing Rs10p and decreasing Rs90p 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 Rs10p and Rs90p 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 Rs90p frequencies but attenuated the severities of both extremes. Overall, Rs extremes jointly regulated Rs trends: China’s brightening was positively contributed by both extremes, while Europe’s brightening was dominated by Rs90p but partially offset by Rs10p. These findings underscore the pivotal role of extremes in shaping overall Rs trends and highlight their importance for accurately assessing regional solar energy availability under global climate change.

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