May 18, 2026

More than three years after lava from Hawaii’s erupting Mauna Loa volcano buried a mile of the road leading to NOAA’s Mauna Loa Atmospheric Baseline Observatory (MLO), road crews have carved a temporary road restoring access to the site.

NOAA technicians, who had to be ferried by helicopter to the facility since 2023 to maintain limited operations, have begun restarting many of the science activities that were suspended on November 27, 2022.

“The reopening of the road to MLO on March 26, 2026, is a monumental win for NOAA and our long-term environmental observations,” said Vanda Grubišić, director of NOAA’s Global Monitoring Laboratory (GML), which operates the site. “After more than three years since being cut off by the 2022 volcanic eruption, the restoration of land access allows us to focus on the future of this pristine observational site and the planned site upgrades.”

Located at an elevation of 3,397 meters (11,135 feet) above sea level on Hawaii’s Big Island, MLO is an internationally renowned atmospheric research facility. Since the 1950s, it has continuously monitored and collected data related to atmospheric composition and surface radiation. MLO’s atmospheric data record is more than 60 years long – the longest record of in-situ observations of important long-lived trace gases. Each successive year of continuous operations at the observatory enhances the value and importance of its data.

The backstory: What happened at the MLO site

When lava erupted from the Mauna Loa caldera and began to flow from fissures in the rift zone on November 28, 2022, it buried about 6,000 feet of road. Lava depth averaged 30-35 feet, but was highly variable and included two large canyons from the main channels of the lava flow. Power lines serving the observatory were also destroyed along that stretch of road.

Ten days after the eruption, GML staff working with partners at University of Hawai’i installed two in-situ carbon dioxide measurement systems on nearby dormant volcano Mauna Kea to replicate the monitoring previously performed on Mauna Loa by NOAA and the Scripps Institution of Oceanography at the University of California San Diego, ensuring continuity of this important measurement record.

In mid-2023, limited power was restored to three key NOAA and two partner observatory buildings by augmenting existing rooftop solar generation and adding battery systems. This enabled the resumption of approximately 33% of the observatory’s atmospheric measurements, including the independent complementary carbon dioxide measurements made by GML and the Scripps Institution of Oceanography. Today, 62 of the 91 daily measurement programs, or 68%, are active.

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