Carnol made his first Luxembourgian team, as a 19-year-old, at the 2008 Summer Olympics in Beijing. He qualified for the men's 200 m breaststroke by eclipsing a FINA B-cut of 2:17.29 from the European Championships in Eindhoven, Netherlands. Carnol challenged seven other swimmers on the second heat including three-time Olympian Jakob Jóhann Sveinsson of Iceland. He raced to third place by 0.29 of a second behind Sveinsson in his lifetime best of 2:15.87. Carnol failed to qualify for the semifinals, as he placed fortieth overall in the evening preliminaries.