A recent study provides the most detailed insight into Earth’s surface temperature fluctuations during the Phanerozoic eon, spanning from 538.8 million years ago to the present. This research reveals that Earth’s temperature has varied more significantly than previously understood and confirms a strong correlation between global temperatures and atmospheric carbon dioxide levels.
The international research team created a comprehensive temperature curve using a method called data assimilation. By analyzing fossil distributions of cold- and heat-tolerant species, along with the chemistry of ancient shells, fossilized microorganisms, and organic matter, scientists were able to reconstruct past ocean temperatures. Additionally, geological indicators such as salt deposits and specific minerals helped map historical climates.
The researchers compiled over 150,000 published data points into a database known as PhanTASTIC (Phanerozoic Technique Averaged Surface Temperature Integrated Curve Project) and integrated this data with modern climate models.
“This method was originally designed for weather forecasting,” says Emily Judd, lead author of the study. “Here, we apply it to hindcast ancient climates rather than predict future weather.”
The team from Arizona collaborated with colleagues at the University of Bristol, generating over 850 climate model simulations based on historical continental positions and atmospheric compositions. By combining these data sources, they constructed a more accurate representation of temperature variations over the last 485 million years.
The findings indicate that global mean surface temperatures ranged from 52 to 97 degrees Fahrenheit (11 to 36 degrees Celsius) during the Phanerozoic. Extreme heat periods were often linked to elevated atmospheric carbon dioxide levels, with solar input playing a lesser role.
Scott Wing, curator of paleobotany at the Smithsonian, notes, “To understand future climate changes, we need to look further back in time to warmer periods, which can provide crucial insights.”
The study reveals that Earth has been significantly cooler in the last 10 to 20 million years compared to the previous 450 million years. However, current anthropogenic climate change is accelerating warming at a rate surpassing even the most rapid warming events of the Phanerozoic.
“Humans and the species we coexist with are adapted to a cooler climate, and rapidly transitioning to a warmer climate poses serious risks,” warns Jessica Tierney, a paleoclimatologist at the University of Arizona. Historical data indicates that episodes of rapid climate change often coincide with mass extinctions.
Although this study represents a significant advancement in our understanding of temperature change, Brian Huber, curator of the micropaleontology collection, emphasizes that it is not the final word. “Researchers will continue to uncover new evidence about the distant past, refining this temperature curve over time.”
The full study, titled “A 485-million-year history of Earth’s surface temperature,” was published in the journal Science. Additional materials and interviews are available from the Smithsonian Institution and the University of Arizona.