(Reuters) - Thousands of protesters kicked off "Climate Week" and filled the streets of Midtown, Manhattan, on Sunday ahead of the U.N. General Assembly this week, calling for President Joe Biden and world leaders to end fossil fuel use.

With parades, concerts, and banging drums, some of the 15,000 expected waved signs that read "End Fossil Fuel Use" and "Fossil Fuels Kill" and "Declare a Climate Emergency."

One man was dressed as a melting snowman warning of rising sea levels. The message was for world leaders to save the planet from the use of oil and gas believed to be driving a warming globe.

Sunday's protests were part of a week-long international effort by Climate Group, a non-profit whose purpose is to drive climate change action and stop global warming, with more than 500 protests planned in the U.S, Germany, England, South Korea, India and elsewhere, totaling 54 countries.

Organizers of the protests expect a global turnout of more than a million people.

"Climate Week NYC is all about getting it done," organizers wrote online. "Through celebrating climate action, challenging ourselves to do more, and exploring ways to increase ambition, Climate Week NYC inspires, amplifies and scrutinizes the commitments, policies and actions of those with the power to make change happen."

Many scientists believe that so-called greenhouse gases caused by burning fossil fuels are warming the world and causing severe weather such as more intense hurricanes, heat waves, floods, wildfires and droughts.

Reductions in CO2 or carbon dioxide emissions are seen as a key element in abating climate change.

The demonstrations take place two months before this year's U.N. COP28 climate summit, where more than 80 countries plan to push for a global agreement to gradually phase out coal, oil and gas.

A recent U.N. report warned that the world was on a dangerous track toward severe global warming, and said more action was needed on all fronts, including drastic drop in coal-fueled power use by 2030, Reuters reported.