NEW YORK — A Manhattan skyscraper that is home to the New York Times became the site of twin daredevil stunts Thursday, with two men scaling the 52-storey office tower within a matter of hours.

The first man, Alain Robert, unfurled a banner as he climbed that said "Global warming kills more people than a 9/11 every week.'' He was arrested when he made it to the top.

Hours later, a second man ascended the building -- a stunt that drew the attention of thousands of onlookers, along with TV cameras that captured the drama in real time. The climber making his way up the building Thursday evening could not immediately be identified, police said.

The facade of the newly constructed building, which the Times moved into only last year, is covered with slats that allowed the men to climb the tower like a ladder.

Robert pumped his fist as he made it to the top, where police took him into custody. Charges against the 45-year-old Robert were pending, a police spokesman said.

Robert's website 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.

The stunt was staged at the Renzo Piano-designed Times building, just a block south of a busy intersection, across the street from the Port Authority bus terminal and not far from Times Square.

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 that 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 website says he climbs even though he suffers from vertigo and is "60 per cent disabled'' from previous accidents. It also says that he has been jailed many times but that 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 than ridiculous stunts like this that endanger the police and public,'' said Councilman Peter Vallone.

"If he wants to climb something, he can climb the walls inside his jail cell at Rikers.''