Nerhagen debuted at the World Championship-level at the World Championships in Antholz-Anterselva in 1983. He also participated in the World Championships in 1985, 1986 and 1987 for Norway. His best individual finish at the World Championships came in 1985 in Ruhpolding where Nerhagen finished 15th in the 20 km individual. His best relay finish at the World Championships was a bronze which came in his first in 1983, which also would be his only medal at the World Championships.