A march on Washington. A climb to the top of an Antarctic mountain. A photo shoot outside the McKeldin Library.

An international protest pushing policymakers to cut atmospheric carbon concentrations took on many forms this weekend, as more than 5,200 broke out across 181 countries. But all the events unified around a common theme: the number 350.

That’s the number of parts per million of carbon dioxide many prominent scientists say should exist in the planet’s atmosphere. Right now, the concentration is 387 parts per million.

The 70 students who gathered in front of the library Friday hoped their demonstration would play a part in pressuring lawmakers to take ambitious steps to reduce the earth’s carbon concentration as a global climate summit approaches in December.

“We want to show that Maryland, as a school and campus, cared as a whole,” said Kate Richard, a member of UMD for Clean Energy, who organized the petition. “Our main goal was to get as many people out for the petition as possible, especially since the main events are all this weekend.”

Environmental activists, members of the improvisational comedy troupe Erasable Inc. and students passing by composed the photo outside McKeldin, as thousands of students assembled in a plaza in the Ethiopian capital, Addis Ababa, on that same day.

In China, college students walked through popular shopping districts in full scuba gear to demonstrate a possible effect of the polar ice caps melting.

The protests continued Saturday, the official 350 Day of Action, when about 25 students from UMD for Clean Energy joined hundreds of others for a march on the White House.

Similar events took place in all 50 states, and organizers declared the day of action the largest environmental demonstration ever  recorded.

The Chesapeake Climate Action Network coordinated the Washington protest, where supporters marched from Malcolm X Park to Lafayette Park, stopping outside the White House to form a “circle of hope” in the hopes of persuading President Barack Obama and other U.S. leaders to create an ambitious treaty at the Copenhagen meeting.

“It was inspirational walking down the street because we held up traffic and people were cheering on the side, which was exciting,” Eric Marshall-Main, a member of UMD for Clean Energy, said. “The rain definitely hampered the turnout, but the energy was still huge.”

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