Ahead of a U.N. summit in New York, vast crowds of children skipped school on Friday to join a global strike against climate change, heeding the rallying cry of teen activist Greta Thunberg and demanding that adults act to stop environmental disaster. It was expected to be the biggest protest ever against the threat posed to the planet by climate change. Shouting slogans and waving placards, children and adults across Asia and the Pacific kicked off the protest, which spread later to Africa and Europe with huge crowds filling the streets.

Some of the first rallies in what is being billed as a "global climate strike" were held in Australia's largest city, Sydney, and the national capital, Canberra. Australian demonstrators called for their nation, which is the world's largest exporter of coal and liquid natural gas, to take more drastic action to reduce greenhouse gas emissions. Organizers estimate more than 300,000 protesters took to the Australian streets in what would be the largest demonstrations in the country since the Iraq War began in 2003.

Friday's mass action set the scene for a range of high-profile climate events in New York. U.N. Secretary-General Antonio Guterres will host an emergency summit on Monday in which he will urge world leaders to raise their commitments made in the 2015 Paris climate accord. The agreement saw countries pledge to limit the long-term rise in the average temperature of the Earth to 2 degrees Celsius (3.6 degrees Fahrenheit) over pre-industrial levels, and if possible, to 1.5 degrees Celsius.