In 1998, Warren-Green became Principal Guest Conductor of the Nordic Chamber Orchestra, taking over as Chief Conductor from 2001 until 2005. From 1998 to 2001, he was Chief Conductor of the Joenkoeping Sinfonietta.
Warren-Green took on the leadership of the Nordic Chamber Orchestra in 1998, eventually becoming the chief conductor from 2001 to 2005. During this time, he also served as the head conductor of the Joenkoeping Sinfonietta from 1998 to 2001.