Christian and other faith communities around the world are hosting 120 events in 35 countries, all calling for governments, businesses and individuals to do more to reduce global warming.
The demonstrations including meditation vigils, fasting, services dedicated to the environment and more.
Catholics and others will also be celebrating the first anniversary of Pope Francis' encyclical (the highest form of pontifical teaching) on the environment.
The two-week Paris climate change summit last November legally-bound countries to keep global warming below 2 degrees Celsius, with 1.5 degrees as a preferable target.
Today's event, called Sacred Earth, Sacred Trust, is urging world nations to make 1.5 degrees the new legally binding limit instead.
Speaking with Premier Revd Fletcher Harper from the charity GreenFaith, which is taking part in Sacred Earth, said: "The Earth is a gift that we absolutely must protect.
"We'd like to see 1.5 [degrees] as an enshrined figure because we know that that mere half-degree difference makes an enormous difference."
"My prayer is that we are given the strength and the courage to reshape our ways and our lives, in ways small and large, to honour and respect that gift."
Listen to Premier's Aaron James speaking to Revd Harper Fletcher:
