A new study provides the most comprehensive view yet of how Earth's surface temperature has changed over the last 485 million years. This research focusses on the Phanerozoic aeon, which spans from 538.8 million years ago to today.
This report was written by David Bressan and published on Forbes on Wednesday.
The study indicates that average global temperatures during the Phanerozoic aeon ranged from 52 to 97 degrees Fahrenheit (11 to 36 degrees Celsius).
In the warmest periods, global temperatures did not drop below 77 degrees Fahrenheit (25 degrees Celsius). Today, the average temperature is about 59 degrees Fahrenheit (15 degrees Celsius).
The study reveals that Earth's temperature has fluctuated more than previously understood. It also confirms a strong link between atmospheric carbon dioxide levels and temperature changes.
While a 2020 study covered the past 66 million years, this new research expands that timeline significantly. It combines temperature records from various sources into a database called PhanTASTIC (Phanerozoic Technique Averaged Surface Temperature Integrated Curve Project). Researchers used data assimilation, a technique originally developed for weather forecasting, to reconstruct ancient climates.
Lead author Emily Judd explains, "We're using this method to hindcast ancient climates instead of predicting future weather." The team compiled over 150,000 published data points and created more than 850 model simulations of Earth's climate at different periods.
The findings show that temperature variations began with the Hirnantian period, marked by significant climate changes from about 460 to 420 million years ago. The coldest phase studied was the Karoo glaciation, which lasted from roughly 360 to 260 million years ago. Overall, the Phanerozoic was mostly characterised by mild to warm climates, with average global temperatures ranging from 52 to 97 degrees Fahrenheit (11 to 36 degrees Celsius).
Today, Earth's average temperature is about 59 degrees Fahrenheit (15 degrees Celsius). The study notes that periods of extreme heat often coincide with high carbon dioxide levels in the atmosphere.
Understanding these historical temperature changes is vital for contextualising current climate change. Scott Wing, a curator at the Smithsonian, emphasises that modern climate predictions require insights from much earlier warm periods. "To understand future climate scenarios, we need to look back to times when the Earth was much warmer," he states.
The research indicates that over the last 10 to 30 million years, Earth has been cooler than during the preceding 300 million years. However, human-induced climate change is warming the planet at an unprecedented rate, outpacing even the fastest historical warming events.
