The Chief Rabbi was among a number of community representatives at an interfaith seminar on the environment, initiated by the London School of Jewish Studies and held at Lambeth Palace on Monday.
Archbishop of Canterbury Dr Rowan Williams was also among more than 60 people who discussed issues including energy conservation in places of worship, theology and the environment and teaching green issues as part of faith education.
The LSJS had approached the Church of England to host the seminar as a way of promoting action on sustainability and climate change across faiths.
"It makes sense to act together as faith communities on issues like climate change," Lord Sacks said. "This is about working side-by-side. This is about standing together, being united."
Lord Marland, Under-Secretary for Energy and Climate Change, urged participants to spread the word that "if you don't think that climate change is happening, or that it isn't made by man, then get real. We need genuine leadership through faiths to get the message across."
During the morning session, the United Synagogue's Peter Zinkin spoke on energy conservation in synagogues. Others involved included Leonie Lewis (Jewish Volunteer Network), David Brown (Jewish Social Action Forum), Solomon Slade (JCC), David Janner-Klausner (UJIA), Neville Sassienie (Board of Deputies) and Shenley Synagogue's Rabbi Natan Levy, head of the LSJS Jewish responsibility unit.
Guests hung letters on a "pledge tree" in the Lambeth Palace grounds, promising to act on the environment. LSJS trustee Sammy Rubin, one of the event's organisers, hoped "these faith leaders will take back their pledges to their own communities to act on the theories we've been discussing".