Saturday's Earth Day follows weeks of extreme weather with temperatures soaring to record highs in Thailand and a punishing heatwave in India, where at least 13 people died of heat stroke at a ceremony last weekend.
Average global temperatures could hit all-time highs in 2023 or 2024, climate scientists have warned.
"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.
Hamid said it feels like "putting your head in the oven" when she visits her hometown of Delhi and London's 2022 heatwave was like "a dystopian film".
"We can't afford that anymore," she said.
Activists led by the Extinction Rebellion group have gathered in London to kick off a four-day action, billed as The Big One, to coincide with Earth Day.
About 30,000 people have signed up for family-friendly rallies and marches, marking a change in strategy for a group known for its disruptive tactics, including blocking roads, throwing paint and smashing windows.
Globally, there has been a flurry of activity in the run-up to Earth Day, with events planned in Rome and Boston and major clean-up campaigns at Lake Dal in India's Srinagar and Florida's hurricane-hit Cape Coral.
In Peru, shamans on Friday made an offering to the "Pachamama", or Mother Earth.
Holding yellow flowers and rattles, the shamans walked around a paper-mache globe as they performed a cleansing ritual.
The ancestral rituals - whose origins lie in the Indigenous cultures of Peru - are done to thank the earth and build awareness of the planet, said Walter Alarcon, the president of the Healing Shamans of Peru International Organization.
Earlier in the week, US President Joe Biden pledged to increase funding to help developing countries fight climate change and curb deforestation in Brazil's Amazon rainforest during a meeting with top world leaders.
Governments have fallen far short of pledges in the 2015 Paris Agreement to limit heating of the climate by shifting off fossil fuels, amid crises including COVID-19, Russia's invasion of Ukraine, food shortages and strained ties between China and the US, the top two greenhouse gas emitters.
A report by the United Nations Intergovernmental Panel on Climate Change (IPCC) says the planet is on track to warm beyond 1.5 degrees Celsius above pre-industrial times - a key threshold for even more damaging impacts - between 2030 and 2035.
"There is a rapidly closing window of opportunity to secure a liveable and sustainable future for all," the IPCC has said.
"The choices and actions implemented in this decade will have impacts now and for thousands of years."
