April 22 (Reuters) - Climate change campaigners gathered outside Britain's parliament building ahead of Earth Day to urge action on global warming, while volunteers worldwide geared up to plant trees and clear trash to mark the 54th annual celebration of the environment. "Climate impacts are here," Areeba Hamid, co-executive director of Greenpeace UK, said on Friday as climate change activists walked down the street outside parliament, some dressed in green costumes and green paint. Activists led by the Extinction Rebellion group have gathered in London to kick off a four-day action, billed "The Big One", to coincide with Earth Day. In Peru, shamans on Friday made an offering to the "Pachamama", or Mother Earth. Holding yellow flowers and rattles, the shamans walked around a papier-mache globe as they performed a cleansing ritual.