Fossils in the Smithsonian’s National Museum of Natural History research collection in its Department of Paleobiology. Credit: Chip Clark.
A new study has charted how Earth’s global temperature has drastically changed over the past 485 million years, driven by carbon dioxide.
The Smithsonian-sparked study co-led by the University of Arizona underscores perils presented by the unprecedented rate of human-made warming.
The team of researchers, including palaeobiologists Scott Wing and Brian Huber from the Smithsonian’s National Museum of Natural History, produced a curve of global mean surface temperature (GMST) across deep time – the Earth’s ancient past stretching over many millions of years.
The new curve reveals that Earth’s temperature has varied more than previously thought over much of the Phanerozoic Eon, the past 540 million years of geological time when life has diversified, populated land and endured multiple mass extinctions.
The curve also confirms that Earth’s temperature is strongly correlated to the amount of carbon dioxide in the atmosphere.
Data assimilation
The team created the temperature curve utilising an approach called data assimilation. This allowed the researchers to combine data from the geological record and climate models to create a more cohesive understanding of ancient climates.
Emily Judd, the lead author of the new paper and a former postdoctoral researcher at the National Museum of Natural History and the University of Arizona, said: “This method was originally developed for weather forecasting. Instead of using it to forecast future weather, here we’re using it to hindcast ancient climates.”
Refining how Earth’s temperature has fluctuated over deep time provides crucial context for understanding modern climate change.
Wing, the museum’s curator of palaeobotany whose research focuses on the Palaeocene–Eocene Thermal Maximum, a period of rapid global warming 55 million years ago, added: “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.
“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.”
The “David H. Koch Hall of Fossils—Deep Time,” a 31,000-square-foot dinosaur and fossil hall at the Smithsonian’s National Museum of Natural History, takes visitors on a journey through deep time to explore ancient ecosystems, experience the evolution of plant and animal life and get up close with some 700 specimens. Credit: Lucia RM Martino, Fred Cochard and James Di Loreto, Smithsonian.
Dominant control
The new curve reveals that temperature varied more greatly during the Phanerozoic than previously thought. Over the eon, the GMST spanned between 52° and 97° Fahrenheit (11° to 36° Celsius).
Periods of extreme heat were most often linked to elevated levels of the greenhouse gas carbon dioxide in the atmosphere.
Jessica Tierney, a palaeoclimatologist at the University of Arizona and a co-author of the new paper, said: “This research illustrates clearly that carbon dioxide is the dominant control on global temperatures across geological time.
“When CO2 is low, the temperature is cold; when CO2 is high, the temperature is warm.”
The findings also reveal that the Earth’s current GMST of 59°F (15°C) is cooler than Earth has been over much of the Phanerozoic.
But greenhouse gas emissions caused by anthropogenic climate change are currently warming the planet at a much faster rate than even the fastest warming events of the Phanerozoic.
The speed of warming puts species and ecosystems around the world at risk and is causing a rapid rise in sea level.
Some other episodes of rapid climate change during the Phanerozoic have sparked mass extinctions.
Tierney explained: “Humans, and the species we share the planet with, are adapted to a cold climate. Rapidly putting us all into a warmer climate is a dangerous thing to do.”
The paper is published in the journal Science.
