The Mauna Loa Observatory marked its 50th anniversary in typically low-key fashion: a little food, a staff meeting and a visit from about 40 preschoolers.

Staff members gathered in Hilo on Wednesday to remember the day 50 years ago — June 28, 1956 — when the original observatory building at 11,141 feet was dedicated and scientists began using it to monitor worldwide climate changes.

After five decades of data collection, the facility remains one of the best spots in the world to gather information about the Earth's atmosphere, said John E. Barnes, the observatory's station manager.

"If you're looking at climate change over decades or longer, we've got the measurements you need," said Barnes. He added that some of the observatory's data is featured prominently in the new Al Gore movie, "An Inconvenient Truth," which documents the rapidly expanding dangers of global warming.

The observatory is known for its longtime documentation of the continuous rise in carbon dioxide levels, a key factor in global climate change because it traps the sun's heat in the atmosphere. Using some observatory figures, the movie documents dramatically a steady rise in the carbon dioxide levels, an increase that has accelerated greatly in the past few years.

The facility, prized by scientists because it offers data taken from a site more than two miles up and far distant from most sources of pollution, also keeps track of more than 50 other chemicals in the atmosphere.

The observatory got its start when federal officials interested in atmospheric research were searching for a place with consistently clear skies and direct, intense sunlight. When they couldn't find anything suitable on the Mainland, somebody mentioned Hawai'i, and the rest is history.

The original research center was a one-story cinder block building built on a concrete pad; today it is part of a 10-building complex. At first, data collection focused on just a few chemicals, compared with the 50 now monitored constantly, Barnes said.

However, the biggest change has been in the use of the Internet to gather and distribute the data remotely and make it available to scientists and the public alike, said Barnes, who started working at the observatory 13 years ago.

"We used to log all the data and occasionally put it on a floppy disk and send it to the Mainland," he said. "Now much of it is available in real time." There's even a 24-hour Web cam that lets viewers check weather conditions outside the observatory.

On most days, two or three workers from the National Oceanic and Atmospheric Administration make the long drive from the main facilities in Hilo to the observatory to check on the instruments and do repairs.

On the anniversary day, however, officials held an all-hands staff meeting in Hilo and linked up by video with the agency's headquarters in Boulder, Colo., where officials, some of whom had worked in the Islands in the past, ate roast pig and watched hula dancers to get in the spirit of the event, Barnes said.

Reach Mike Leidemann at mleidemann@honoluluadvertiser.com.