Welby, in his first speech to a general synod as head of the church and of the Anglican Communion, stopped short of calling for a change in the church's opposition to same-sex marriage, The Guardian reported. But he said there has been "a revolution in the area of sexuality."
During the House of Lords debate on same-sex marriage, there was "noticeable hostility to the view of the churches," he said.
"Anyone who listened to much of the same-sex marriage bill second reading debate in the House of Lords could not fail to be struck by the overwhelming change of cultural hinterland," he said. "Predictable attitudes were no longer there. The opposition to the Bill was utterly overwhelmed."
Welby called on the church to fight prejudice against homosexuals. Specifically, he said the church is developing a program to deal with homophobic bullying in its 5,000 schools.
The synod is also scheduled to discuss the controversial issue of women bishops after a vote in November that kept the status quo. Delegates are expected to vote Monday on whether to change the policy.
"This synod had a shock last November, but there is here assembled, in weakness or confidence, in all sorts of fear and lack of trust, people with the faith and wisdom who in grace will seek the way to the greater glory of God," Welby said in his speech.