"Our findings are important because they identify a hidden source of CO2 to the atmosphere during moments in Earth's past when climate has warmed abruptly and stayed warm much longer than we expected," said Benjamin Black, study lead and associate professor in the Department of Earth and Planetary Sciences at Rutgers. "We think we have figured out an important piece of the puzzle for how Earth's climate was disrupted, and perhaps just as importantly, how it recovered."
Today, human activities release far more CO2 than all active volcanoes combined, but this study offers clues about Earth's potential recovery if human-driven emissions decrease. Black explained, "Earth has natural climate control systems - sort of like the thermostat in your house. The question is - are there thresholds beyond which those climate control systems start to break down, making it much harder for climate to recover?"
Scientists have long been puzzled by the slow recovery of Earth's atmosphere following the end-Permian mass extinction about 252 million years ago, the most significant loss of biodiversity in Earth's history. Massive volcanic eruptions in Siberia were linked to the extinction, yet Earth's climate took nearly 5 million years to stabilize after the eruptions subsided.
"This delayed recovery has long puzzled scientists. Earth's natural thermostat seems to have gone haywire during and after this event," Black noted. Observing similar patterns across other times marked by large-scale volcanic activity, the team investigated what might be driving the extended warming periods.
Through analyses of ancient lavas, computer simulations of Earth's internal melting processes, and examination of sedimentary rock climate records, researchers identified sustained CO2 emissions from "cryptic carbon" deep in volcanic regions. This magma-based CO2 released from beneath the surface created prolonged greenhouse conditions. "We call this CO2 from the subsurface magma 'cryptic carbon' because it comes from magmas lurking deep in the system," said Black. "It's as if the volcanoes were releasing carbon from beyond the grave."
According to Black, these findings reveal an unexpected source of atmospheric CO2 linked to ancient climate warming phases. This suggests that Earth's "thermostat" may be more resilient than previously thought. "If this is true, it could be good news for Earth's recovery after human-driven climate warming," he added. "It means that if we stop turning the thermostat up, on geologic timescales of hundreds of thousands to millions of years, climate can recover."
However, Black emphasized that cryptic carbon emissions from volcanoes are not a factor in today's climate crisis. "The type of volcanism we are investigating is rare, capable of generating enough magma to cover the continental United States half a kilometer deep in lava," he said. "This kind of volcanism has not occurred for 16 million years. All the volcanism taking place on the planet today releases less than one percent as much carbon dioxide as human activities."
The team aims to learn from these historical eruptions to better understand modern climate dynamics. "These ancient eruptions appear to be some of the only events in Earth's history that release carbon on the same scale as humans are doing today," Black explained. "So by studying these eruptions in the deep past we can learn more about how Earth's climate systems respond to massive release of carbon to the atmosphere."
This research marks the start of a multi-year National Science Foundation-funded project exploring cryptic carbon's role in climate recovery following major climatic disturbances. This summer, the team explored the Wallowa Mountains in northeastern Oregon - nicknamed the "Alps of Oregon" - where vast magmatic sheets reveal remnants of magma that once lay deep within the Earth and now aid in deciphering past climate impacts of volcanic CO2 emissions.
Research Report:Cryptic degassing and protracted greenhouse climates after flood basalt events
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Rutgers University
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