A new study offers the most detailed look yet at Earth’s surface temperature changes over the past 485 million years. The research, published in the journal Science, reveals significant variations in global temperatures throughout the Phanerozoic eon, which began about 538.8 million years ago and continues to the present. The international team of researchers used a novel approach to reconstruct ancient temperatures.
They combined over 150,000 data points from various sources, including the fossil distribution of temperature-sensitive animals and plants, preserved organic matter, and geological indicators like salt deposits and specific minerals. “This method was originally developed for weather forecasting,” explained lead author Emily Judd, a former postdoctoral researcher at the University of Arizona. “Instead of using it to forecast future weather, here we’re using it to hindcast ancient climates.”
The findings indicate that the Phanerozoic was characterized by mild to warm climates, with global mean surface temperatures ranging from 52 to 97 degrees Fahrenheit (11 to 36 degrees Celsius).
The coldest period occurred approximately 360 to 260 million years ago. Notably, during the warmest periods, global temperatures did not drop below 77 degrees Fahrenheit (25 degrees Celsius).
Earth’s historical temperature variations
Over the last 60 million years, Earth has experienced a cooling trend, with the current global average temperature around 59 degrees Fahrenheit (15 degrees Celsius). The study also highlights that periods of extreme heat often corresponded with elevated levels of atmospheric carbon dioxide. “This research illustrates clearly that carbon dioxide is the dominant control on global temperatures across geological time,” said co-author Jessica Tierney, a paleoclimatologist at the University of Arizona.
The study underscores that much of the last 10 to 30 million years have been notably cooler than the preceding 300 million years. Tierney emphasized the implications, stating, “Humans and the species we share the planet with are adapted to a colder climate. Rapidly moving towards a warmer climate is dangerous.”
While this study represents the most detailed analysis of Earth’s temperature changes to date, researchers acknowledge it is a work in progress.
“This isn’t the final curve,” said co-author Brian Huber, curator of the micropaleontology collection at the Smithsonian National Museum of Natural History. “Ongoing research will continue to uncover additional clues, further refining our understanding of Earth’s climatic history.”
The full study, titled “A 485-Million-Year History of Earth’s Surface Temperature,” provides crucial insights into the link between atmospheric carbon dioxide and global temperatures, offering a glimpse into potential future climate conditions if greenhouse gas emissions continue to rise.
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