United States Conference of Catholic Bishops From 1991 to 1998 he led the Office of International Justice and Peace, what he then described as the "social policy arm of the Roman Catholic bishops of the United States," when it was called the United States Catholic Conference (USCC). In 1991 for the pastoral "Renewing the Earth," Christiansen served as lead advisor. This writing and research formed a basis for his future work and commentary on the environment. In 1993 he was lead staff member for "The Harvest of Justice Is Sown In Peace," a landmark peace pastoral which established the foundation for the USCCB's policies after the Cold War. From 1998 to 2004 he was counselor for International Affairs.
Consultant to the Vatican He was a frequent consultant to the
Holy See on issues that included nuclear disarmament. He also served on the Holy See delegation that participated in the negotiation of the
Treaty on the Prohibition of Nuclear Weapons during the summer of 2017. After Pope Francis, under the direction of Cardinal
Peter Turkson, hosted a conference—Prospects for a World Free from Nuclear Weapons and for Integral Disarmament—at the Vatican in November 2017. Christiansen produced two books based on it, at the direct request of the Holy See.
Work in the Middle East, Ecumenical Dialogue At the bishops' conference he became more interested in the Middle East. He worked with
Michel Sabbah, the emeritus Latin Patriarch of Jerusalem for many years, and wrote an introduction to his book. Sabbah named Christiansen a Canon of the Holy Sepulchre of Jerusalem. He was also a member of the
Atlantic Council's Middle East Task Force, as part of his ongoing work in the region. In broader ecumenical efforts, Christiansen served as a consultant to the Pontifical Council for Promoting Christian Unity for the Mennonite-Catholic Dialogue, honoring
Mennonites as members of the historic
Peace Churches. In a common concluding statement at the Mennonite World Conference 2000, the Catholic and Mennonite participants agreed that "the church is called to live as an efficacious sign and an instrument of peace overcoming every form of enmity and to reconcile all peoples in the peace of Christ".
Editor-in-chief of America magazine He served at this national Jesuit publication based in Manhattan, later restyled as
America: The Jesuit Review, for 10 years from 2002 to 2012. For the last seven years, from 2005 to 2012, he was editor-in-chief, succeeding
Thomas J. Reese SJ, and he oversaw the magazine's 100th anniversary. After Matt Malone SJ succeeded him as editor-in-chief in 2012, he returned to Georgetown University. During his tenure as editor-in-chief, he exhorted
James J. Martin SJ to travel to the Holy Land for a planned book,
Jesus: A Pilgrimage. Martin recalled Christiansen's inspiration for the book both in an article for
America and in a homily. The book became a Christopher-award-winning,
New York Times bestseller. On April 20, 2022, Martin offered the homily at Christiansen's funeral at
Holy Trinity Catholic Church in Washington, D.C., the Jesuit parish church next to Georgetown University, accompanying the celebrant, G. Ronald Murphy SJ, and he remembered the incident with great affection and credit to his friend.
University distinguished professor In 2013, Christiansen returned to Georgetown University in a full-time role as a senior fellow at the Berkley Center for Religion, Peace, and World Affairs and Distinguished Professor of Ethics and Human Development in the School of Foreign Service, posts he held until his death. He continued to advise students and oversee his final book until April 2022. Previously, sometimes between earlier periods of service at Georgetown University, he was associate professor of theology and staff fellow of the
Kroc Institute for International Peace Studies at the
University of Notre Dame (1986–1990), where he was a member of the founding team. At the Jesuit School of Theology/Graduate Theological Union-Berkeley (now the
Jesuit School of Theology of Santa Clara University), from 1981 to 1986, he was assistant professor of social ethics. Additionally, from 1982 to 1986, he was director of its Center for Ethics and Social Policy. The majority of his academic career was spent at Georgetown University.
Pastoral care of older adults Christiansen had a deep personal interest in the pastoral needs of people in residential nursing facilities or aging in place at home, and he visited those in long-term care when he was able, hearing confessions and celebrating the Eucharist. His 1982 doctoral dissertation at Yale was titled "Autonomy and Dependence in Old Age: An Ethical Analysis" under the direction of Sister
Margaret Farley R.S.M., and he retained a lifelong attentiveness to people experiencing issues attendant with such care. ==Death==