From the first birds and fish to pine trees, dinosaurs, woolly mammoths and humans, most life on Earth has evolved and flourished over the last roughly 500 million years. A new study documents how the Earth’s temperature changed in that time frame — carbon dioxide has been a driving cause of historic temperature increases.
Using proxy data, geologic studies and climate models, researchers found that over the last 485 million years, the global mean surface temperature (GMST) of the Earth has varied between 11° Celsius (52° Fahrenheit) and 36°C (97°F). In other words, the average temperature of the Earth has stayed within that 25°C (45°F) degree window for the last half a billion years. High temperature periods often tracked with elevated atmospheric carbon dioxide (CO2) levels.
“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 study said in a statement. “When CO2 is low, the temperature is cold; when CO2 is high, the temperature is warm.”
The current GMST of the Earth is approximately 15°C (59°F).
“Right now, we are still in an ice age,” Brian Huber, study co-author and paleobiologist with the Smithsonian National Museum of Natural History in the U.S., told Mongabay in a phone call. However, Huber added that based on what’s known from studies of past climate warming events, “we are warming the Earth faster than any other natural event that’s happened in geologic history.”
Human-caused carbon emissions are the source of this rapid warming. Since the industrial revolution, global atmospheric carbon levels have risen from 280 parts per million (ppm) to nearly 420 ppm today.
You would have to go back 3 million years to get to an Earth with current atmospheric carbon levels. The Earth was upward of 4°C (7.2°F) warmer then and the sea level as much as 80 feet higher.
Huber said that past spikes in carbon and commensurate warming, like the Cenomanian-Turonian boundary from 94 million years ago, are associated with extinctions, though not necessarily mass extinctions. At the time, warming was much slower than what the Earth experiences today, and Huber cautioned that many species, especially humans, may have a hard time adapting.
“Life adapts and survives, and we will survive one way or the other, I expect. But it doesn’t mean it’s not going to hurt, and it’s not going to hurt big time,” Huber added.
Banner image: via Wikimedia Commons (CC BY-SA 4.0)
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