Nussbaum joined the Department of Foreign Affairs and International Trade in 1996, working on international environmental law files in the Department's Legal Bureau and then international trade issues before moving to New York to join Canada's United Nation's Security Council Team in 1999. He then worked as Chief of Staff to Robert Fowler, Canada's Sherpa to the 2002 G7 Summit in Kananaskis, Alberta. After his posting to Geneva at the Canadian Mission to the World Trade Organization, Nussbaum returned to Ottawa in 2005 to work as Director of US Relations, then Director General of the Corporate Secretariat at Global Affairs Canada before moving to the Privy Council Office as Director of Social Development Policy.[9] In 2010, he was appointed Director General of Strategic Policy at the then Canadian International Development Agency (since merged with Global Affairs Canada). In that position he was responsible for the agency's policy development and research work, economic analysis and international strategy, including policy engagement with multilateral organizations and other donors.[10] He co-chaired the International Network on Conflict-Affected and Fragile States (INCAF) housed at the OECD.[11]
In 2014, Nussbaum took a leave of absence from the Canadian Foreign Service to run against Peter Clark, the incumbent Councillor for Rideau-Rockcliffe Ward,[12] whom he beat, attaining almost 50 percent of the vote.[13][14] In December 2014, Nussbaum was the only freshman Councillor to be appointed as a Committee Chair.[15] He ran for re-election in the 2018 Ottawa Municipal Election and won with over 80 percent of the vote, before leaving to head up the National Capital Commission.
Personal life
Nussbaum is married to Dr. Elizabeth Muggah, past President of the Ontario College of Family Physicians and an Ottawa-based Family Doctor and University of Ottawa Associate Professor.[16] They have two daughters.[17]