In Helsinki, more than a thousand people marched from the Narinkka Square to the Senate Square demanding a carbon-free Helsinki as well as showing opposition to nuclear energy.
According to international news agency AFP, 2,500 marches were organised on Sunday across the globe.
According to AFP, the march in New York saw some 310,000 people taking part including United Nations Secretary-General Ban Ki-moon, former US Vice President Al Gore and actor Leonardo DiCaprio.
The United Nations will host a summit on climate change in New York on Tuesday.
