There is an ongoing debate on whether the observed decadal variations in surface solar radiation, known as "dimming and brightening", are a global or just local phenomenon. We investigated this issue using a comprehensive set of long-term sunshine duration records from China, which experienced a rapid growth in urbanization during past decades. 172 pairs of urban and nearby rural stations were analyzed over the period 1960–1989 ("dimming phase") and 1990–2013 ("brightening phase").

There is increasing evidence that the amount of solar radiation incident at the Earth's surface is not stable over the years but undergoes significant decadal variations. Here I review the evidence for these changes, their magnitude, their possible causes, their representation in climate models, and their potential implications for climate change.