Mauna Loa Observatory

The weather measurements made here are so sensitive that when the observatory was built in 1956 scientists asked the national park to ban stoves at the summit cabin, fearing those emissions 6 miles away would throw off their readings. The park didn't, but the observatory managed to adjust. It has continuously recorded carbon dioxide (CO₂) and other human-produced greenhouse gas levels ever since, defining much of our understanding of global climate change. Tours of the facility are by appointment only.

Charles Keeling conducted much of the initial work at MLO, and was the first to consistently measure CO₂ at the same location. This allowed him to observe the steadily increasing levels – a trend referred to as the Keeling Curve – which is what first alerted scientists to the threat of global climate change.

Today, the observatory measures dozens of atmospheric gases, including methane, carbon monoxide, propane and nitrous oxide, and records particulate matter (pollution). The observations are taken when weather conditions ensure they capture an oceanic breeze untainted by Hawaiʻi's cities or volcanic eruptions.

Lonely Planet's must-see attractions

Nearby attractions

1. Lua Poholo

3.15 MILES

A deep pit crater on the northeast edge of Mauna Loa's summit caldera. The crater collapsed inward when lava left the summit.

2. Mauna Loa

4.83 MILES

The world's largest subaerial (above water) volcano, Mauna Loa (Long Mountain) is so massive that you feel its presence more than see it. Even when it…

3. Mauna Loa Lookout

12.49 MILES

A narrow, winding and potholed drive along lonely Mauna Loa Rd passes heavily forested kipuka (volcanic oases) as you come ever closer to the world's most…

4. Humu‘ula Sheep Station

13.67 MILES

For 100 years these pastures were filled with sheep, and that historical legacy is marked by nearby rock walls stacked by Japanese laborers and the Humu…

5. Gilbert Kahele Recreation Area

15.22 MILES

The only public facilities along Saddle Road make for an altogether pleasant stop. Clean restrooms and a playground with plenty of ropes to climb mean it…

6. Footprints

18.01 MILES

A short, 0.8-mile walk down the Mauna Iki trail from the Kaʻu Desert trailhead on Hwy 11 brings you to a field of scattered footprints preserved in…

7. Apollo Valley

19.25 MILES

Just past Mile 4 on the east side of the summit road, a washed-out valley full of grayish glacial till and rocks is a dead ringer for the surface of the…

8. Wood Valley Temple

19.39 MILES

Its official name, which translates to 'Immutable Island of Melodious Sound,' perfectly captures the valley's wind and birdsong. Just outside Pahala, you…