UV-B treated plants suffered a down-regulation of photosynthesis during the first days of exposure and at maturity, with a transient recovery at veraison. Carbon fixation rates were always higher under elevated CO2–temperature. UV-B radiation elicited both enzymatic and non-enzymatic antioxidant responses, leading to a eustress state, which may have contributed to reduce the signs of oxidative damage induced by elevated CO2–temperature. The photosynthetic performance of fruit-bearing cuttings was strongly correlated to changes in berry ripening rates. The hastening effect of climate change conditions on grape ripening, associated to higher rates of carbon fixation, was attenuated by UV-B radiation.