Hawaii 's Mauna Loa Observatory: Monitoring the atmosphere from the world's biggest mountain

Forrest M. Mims III

Thanks to laptop computers and the Internet, this column can be prepared from distant places. Today's installment is coming from the most remote site on one of the most remote islands on the planet.

The island is Hawaii , the largest in a long chain of volcanic islands in the Pacific Ocean .

Hawaii is still growing. Kilauea , its most active volcano, has been pouring molten lava into the sea virtually nonstop since 1983.

Kilauea's huge crater looks big up close, but it's merely a blister on the side of Mauna Loa , the world's largest volcano. Perched on the slope of Mauna Loa 11,200 feet over the ocean is the Mauna Loa Observatory (MLO, see Fig. 1). This column is being prepared from a small office at MLO. During the week several scientists are working here. Because it's a weekend, I'm alone.

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Figure 1. Hawaii 's Mauna Loa Observatory is 3,400 meters (11,200 feet) over the Pacific Ocean . The instruments in the foreground monitor solar ultraviolet and visible wavelengths of sunlight for the US Department of Agriculture's UV-B Research and Monitoring Program managed by Colorado State University. The dome houses a Dobson spectrophotometer for measuring the ozone layer. The building at center right is the original Mauna Loa Observatory structure dedicated in 1956. It is now known as the Keeling Building in recognition of Charles Keeling's pioneering measurements of the increase in carbon dioxide in the atmosphere. Photograph by Forrest M. Mims III.

Most people think MLO is one of the astronomy observatories atop Mauna Kea , the giant volcano that looms across the horizon outside my window. Those observatories look at stars and planets. MLO looks at our home planet.

More than 200 aspects of the atmosphere and sunlight are measured by instruments installed in a cluster of buildings on a 4-acre site. All this began with a simple concrete block building 50 years ago. That building is now famous. It is home to the late Charles D. Keeling's instrument that discovered that carbon dioxide is increasing each year, mainly because of the burning of coal and petroleum.

Carbon dioxide is a “greenhouse gas.” Most sunlight passes right through it on the way to the surface. When sunlight strikes plants, rocks, soil, roads and the places where you and I live and work, they become warm and emit the infrared rays we sense as heat. Carbon dioxide blocks those infrared rays when they travels up into the sky, thus acting as a transparent shield that lets in sunlight while trapping heat.

Water vapor does the same thing on a grander scale. Water vapor is king of greenhouse gases. Without it, earth would be frozen solid.

There is great concern that the rapid increase in carbon dioxide will tilt the greenhouse effect so that the climate will warm. But I'm much more interested in water vapor, which is one reason I've been coming to this giant volcano in Hawaii at least annually since 1992. The ultra clear and dry air here is perfect for calibrating my homemade water vapor instruments.

It's cold and lonely up here, and the nearest beach is miles away. You can see it through binoculars. But over the years, MLO has become home away from home.

Today began with an astonishing sunrise. The shadow of the giant Mauna Loa formed a dark triangle in the pink twilight glow opposite the rising sun.

The daily calibration routine requires pointing my instruments at the sun as it rises in the sky. Any boredom is quickly relieved by glancing over at the giant Mauna Kea resting under a crystal clear, azure sky.

"World of Science" columns are selected and sometimes revised from columns published in the San Antonio Express-News or the Seguin Gazette-Enterprise. The columns are intended for a general audience. Forrest M. Mims III and his science are featured online at www.forrestmims.org and www.sunandsky.org .