NEW YORK - The spectacle of two climbers scaling the 52-story New York Times tower raised questions about the building's security and how to deter future daredevils.

"We can't celebrate it because it is dangerous - and it's illegal," said Joe Iurato, editor of New York-based Urban Climber magazine. "But some people have a strong urge to climb - even when there aren't any mountains in their back yards."

Thursday morning, Frenchman Alain Robert took on the Times' soaring new tower on Manhattan's West Side in the name of global warming. New Yorker Renaldo Clarke followed that evening, struggling to the top to promote awareness about the dangers of malaria.

Each was arrested on the roof. Both men faced charges of reckless endangerment, criminal trespass and disorderly conduct; Robert also was charged with making graffiti for posting a bright green banner on the 17th floor that read: "Global warming kills more people than a 9/11 every week."

Times officials wouldn't specify how they planned to keep away future climbers. "In addition to added security, design modifications are under consideration," spokeswoman Abbe Ruttenberg Serphos said in a statement.

Iurato noted that while hundreds of thousands of people are proficient at rock climbing, far fewer have the skill to climb a building solo without rope or harness.

But he also said he wasn't surprised by the two climbs because the Renzo Piano design - which features horizontal slats on the exterior - was too tempting. "It looks like a 400-foot ladder," he said.

Robert acknowledged yesterday that he chose the Times building because in terms of difficulty, "It's easy - 1 on a scale of 10."

The 45-year-old Frenchman has scaled more than 80 structures, including the Empire State Building, the Golden Gate Bridge, Chicago's Sears Tower and the Petronas Towers in Kuala Lumpur, Malaysia - twice. *