Hundreds of people craned their necks to watch his climb up the exterior of the new tower designed by Renzo Piano. Workers cheered from a construction site across the street, and Robert pumped his fist.
Police took him into custody at the top. Charges against the 45-year-old Robert were pending, a police spokesman said.
Robert's Web site says he has climbed more than 70 skyscrapers around the world. He was arrested in February after climbing a 42-floor building in Sao Paolo, Brazil.
Thursday's stunt was staged at the Times building, just a block south of the busy intersection at Eighth Avenue and 42nd Street, across the street from the Port Authority bus terminal. The building's facade is covered with slats that Robert climbed like a ladder.
A spokeswoman for the Times, Catherine Mathis, said no one at the newspaper knew of Robert's plan in advance.
The Times itself has "a very green building," Mathis noted. "We wanted to minimize our environmental footprint." She said the ceramic slats save energy by reducing the amount of heat and light entering the building.
Robert said in a news release he was climbing to mark World Environment Day and "to create support for far greater and urgent action from world leaders on global warming."
His Web site says he climbs even though he suffers from vertigo and is "60 percent disabled" from previous accidents. It also says he has been jailed many times but it does not matter because he "would rather stay in a prison than in a hospital."
One city councilman is hoping that Robert gets to know what the inside of a New York City jail looks like.
"Regardless of the cause, in this day and age the police department has more important things to worry about then ridiculous stunts like this that endanger the police and public," said Councilman Peter Vallone Jr. "If he wants to climb something, he can climb the walls inside his jail cell at Rikers."
