From ice to heat: 485 million years of climate change on Earth

A partnership between researchers from the Smithsonian and the University of Arizona, both in the US. produced One of the most complete records of temperature on Earth over the last 485 million years.

The study, published in the journal Science, is a long-term geological record of global mean surface temperature (GMST) as well as an inventory of the relationship between GMST and atmospheric carbon dioxide (CO2) concentrations.

The climate underwent many extreme changes during the last half-billion years of life on Earth, which coincided with the Phanerozoic, the planet’s most recent geological period. Ocean levels and ice sheets changed, the composition of the atmosphere changed; not to mention biological evolution marked by dramatic extinction events.

Providing a record of Earth’s temperature over the past nearly 500 million years, the aim of the study is to help scientists understand how this all happened and predict what might happen if we continue to add carbon to the atmosphere. “This research clearly shows that carbon dioxide has been the dominant source of control over global temperatures throughout geological time“, emphasizes co-author Jessica Tierney in a statement.

Analyzing the world’s past climate change

To create the giant temperature curve, the team adopted an approach called Phanerozoic data assimilation (PhanDA). Originally designed for weather forecasting, the method Data from climate models were combined with data from geology to determine how climate has changed over the last 485 million years.

“Instead of using it to predict future weather, here we use it to predict ancient climates,” according to the statement. This made it possible to refine the Earth’s temperature fluctuations to understand current climate changes. But co-author Scott Wing, a paleobotanist at the National Museum of Natural History, warns that even in the last few million years, nothing “like we would expect in 2100 or 2500” has happened.

This specifically refers to the period of rapid global warming that occurred 55 million years ago, known as the Paleocene-Eocene Thermal Maximum. “We need to go further back in time, Periods when the Earth was really warm, because that’s the only way we can better understand how the climate may change in the future“, compares.

Earth’s climate changes in the Phanerozoic

The new study shows that overall GMST varied between 11°C and 36°C during the Phanerozoic; This is a much larger swing than previously thought. Greenhouse climates (periods when global temperatures were higher) were also much warmer than previously predicted. These periods of extreme heat have been associated with higher CO2 concentrations in the atmosphere..

Another surprising discovery was this: Earth is technically living in an ice ageOur GMST today (15 °C) is colder than the planet was during most of the Phanerozoic. But greenhouse gas emissions caused by anthropogenic climate change are warming the planet.

This rate of warming not only causes sea levels to rise dangerously, but also puts global species and ecosystems at risk. Because humans and other species adapt to a cold climate, Tierney explains, “To quickly push us all into a warmer climate is a dangerous thing.”

Although this new study is the most comprehensive analysis of planetary temperature variations ever conducted, it is an ongoing project, according to co-author Brian Huber of the Smithsonian National Museum of Natural History. “Researchers will continue to uncover additional clues to the deep past, which will help revise this curve in the future,” he says.

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