Climate activists form the number 350 -- representing 350 parts of carbon dioxide per million parts of atmosphere -- on the steps of the Opera House in Sydney, Australia, on Saturday, Oct. 24.
Organizers said 4,000 similar events were held around the world to pressure governments to reduce CO2 levels to 350 ppm from nearly 390 at present.
This climate activist and others with her took to the streets in downtown Hong Kong on Saturday. The global protest was held 50 days before nations start a summit in Copenhagen, Denmark, to try to work out a new climate treaty.
Developing countries argue that the industrial world produced most of the heat-trapping greenhouse gases and should bear the costs of fixing the problem. Wealthy nations say all countries — including growing polluters India and China — have to agree to broad cuts in emissions.
In Berlin, Germany, climate activists on Saturday staged a performance of German Chancellor Angela Merkel being pulled by both good and evil.
Danish Prime Minister Lars Lokke Rasmussen, host of the upcoming climate summit, said Saturday that recent talks have been "painfully slow. Clearly, at current speed, we will not make it in the remaining weeks."
"The sense of urgency is setting in as we approach the deadline," he added.
In Mumbai, India, climate activists form a human chain on Saturday. The full banner reads: Warm the Earth with Love not with carbon dioxide.
Activists in Paris, France, hold alarm clocks and mobile phones set to ring simultaneously during a protest Saturday.
The protests in Mumbai on Saturday included this one where activists posed as victims of climate-induced disasters.
Many scientists expect warming to lead to widespread drought, floods, higher sea levels and worsening storms. Even a 3.6-degree-Fahrenheit temperature rise could subject up to two billion people to water shortages by 2050, according to the U.N. Intergovernmental Panel on Climate Change.
In Istanbul, Turkey, climate activists carry an "Earth ball" and a peace flag during a rally Saturday.
In Kiev, Ukraine, these two climate activists at a rally Saturday didn't let a few leaves get in their way.
Hundreds of kayakers, canoeists and standup paddleboarders gather on Willamette River in Portland, Ore., Saturday for their version of a climate protest.
Dozens of activists take over New York City's Times Square for a brief period Saturday.
At a beach near Caracas, Venezuela, activsts prepare their human chain Saturday. Their protest aimed at showcasing the danger of rising seas.
Climate activists march through downtown Vancouver, B.C.
In Bolivia, this man was part of a group that traveled to the Chacaltaya Glacier in the Andes to make a climate statement. The glacier was famous for having the world's highest ski run but since the mid-1990s it has not had enough snow for skiing.