11:36 a.m. (0936 GMT, 5:36 EDT)
The Vatican spokesman says that in the 25 years that he has worked there, he has never seen as much prolonged, global and intense anticipation for a single document as with the release of Pope Francis' environment encyclical.
The Rev. Federico Lombardi started a news conference to launch "Laudato Si" (Praise Be) that "clearly humanity has wanted to hear the word of the pope, considering it important and timely."
The news conference was packed, and held in a Vatican audience hall rather than the normal press briefing room to accommodate the crowds.
Lombardi said: "On this day we feel the universal church united with the pope."
Over the past month, the Vatican sent bishops around the world preparatory documents to help them explain the issue to their flocks. Two days ago, Francis sent a copy of the encyclical itself to each bishop, along with a hand-written letter introducing it.
10:40 a.m. (0840 GMT, 4:40 a.m. EDT)
The Vatican is launching Pope Francis' environment encyclical with a high-level press conference aimed at inspiring action from people of all faiths and no faith at all to combat climate change.
Speakers are expected to include Cardinal Peter Turkson, whose Vatican office penned the first draft of the document.
Joining him will be Metropolitan of Pergamon John Zizioulas, a leading theologian in the Greek Orthodox Church, which has prioritized protecting God's creation.
German scientist John Schellnhuber, an atheist, is credited with coming up with the goal to keep global warming from increasing by 2 degrees Celsius over pre-industrial levels.
Economist Carolyn Woo is head of Catholic Relief Services, the overseas humanitarian agency of the U.S. church.