Earth’s surface temperature heating more rapidly than it has in past 485 million years, scientists say

(CN) — Over the past 485 million years, the global mean surface temperature of the Earth has experienced drastic changes, more than previously thought, according to a new scientific paper.

A team of researchers created a curve showing the changes in global mean surface temperature spanning 485 million years using data assimilation to combine data from climate models and from the geologic record to understand ancient climates. The research method was originally developed to forecast weather.

“Instead of using it to forecast future weather, here we’re using it to hindcast ancient climates,” Emily Judd, lead author of the paper and former postdoctoral researcher at the National Museum of Natural History and the University of Arizona, said in a statement.

The paper, titled “A 485-million-year history of Earth’s surface temperature,” was published Thursday in the journal Science and co-led by researchers at the Smithsonian and University of Arizona. It is the latest development in a research effort that kicked off in 2018.

The findings from the research show just how much Earth’s surface temperature has changed and fluctuated over time, providing an important window into understanding modern climate change.

“If you’re studying the past couple of million years, you won’t find anything that looks like what we expect in 2100 or 2500,” Scott Wing, a paleobiologist with the Smithsonian, said in a statement.

Wing’s research specializes in the Paleocene–Eocene Thermal Maximum, a period of time 55 million years ago that experienced rapid global warming.

“You need to go back even further to periods when the Earth was really warm, because that’s the only way we’re going to get a better understanding of how the climate might change in the future,” Wing said.

The global mean surface temperature curve shows a greater variation of temperature within the Phanerozoic Eon — the current eon in Earth’s geological history, spanning the past 540 million years — than scientists previously thought. The curve also indicates a strong correlation between the amount of carbon dioxide in the atmosphere and Earth’s surface temperature.

“This research illustrates clearly that carbon dioxide is the dominant control on global temperatures across geological time,” Jessica Tierney, a paleoclimatologist at the University of Arizona and a co-author of the new paper, said in a statement. “When CO2 is low, the temperature is cold; when CO2 is high, the temperature is warm.”

Throughout the eon, the curve shows that the global mean surface temperature has fluctuated between 52 and 97 degrees Fahrenheit. Earth’s current global mean surface temperature is 59 degrees Fahrenheit, cooler than temperatures seen during much of the Phanerozoic Eon.

Researchers said the periods of extreme heat seen in Earth’s history were linked to higher levels of greenhouse gas carbon dioxide in the atmosphere. While Earth’s current global mean surface temperature is lower than the historic highs seen in the eon, human-caused greenhouse gas emissions are causing the planet to warm at a much faster rate than seen throughout even the most rapid warming periods of the Phanerozoic era.

Rapid climate change periods during the Phanerozoic Eon have led to mass extinctions, and higher rates of warming threaten the world’s ecosystems and species at risk.

“Humans, and the species we share the planet with, are adapted to a cold climate,” Tierney said. “Rapidly putting us all into a warmer climate is a dangerous thing to do.”

In 2018, the Smithsonian developed a new hall in the museum using fossils to highlight how the planet’s temperature has changed. When the team realized there was not a reliable temperature curve to represent the Phanerozoic Eon, they started the Phanerozoic Technique Averaged Surface Temperature Integrated Curve (PhanTASTIC) Project to produce a temperature curve.

Before the project began, the team realized that the fragmented nature of fossil record contributed to the lack of one cohesive temperature curve spanning the half-a-billion-year time period. Relying solely on fossils can provide clues into ancient temperatures, but provides limited information only about a certain area during a certain period of time.

“It is like trying to visualize the picture of a 1,000-piece jigsaw puzzle, when you only have a handful of pieces,” Judd said.

Using data assimilation, the team reconstructed climatic snapshots of Earth across various points of the Phanerozoic using over 150,000 published data points from five different geochemical archives for ancient ocean temperatures combined with computer simulations of past climates.

The ancient ocean temperature data points came from preservations from fossilized shells and other fossilized organic matter. Researchers at the University of Bristol then created over 850 model simulations of the Earth’s climate during different periods in time based on atmospheric composition and continental position. The team then combined the two lines of evidence to create a more accurate curve showing Earth’s historical temperature variance using data assimilation.

While the paper represents a more complete study of the planet’s temperature than produced before, the researchers say more work needs to be done.

“We all agree that this isn’t the final curve,” Smithsonian paleobiologist Brian Huber said. “Researchers will continue to uncover additional clues about the deep past, which will help revise this curve down the road.”