Reconstructing the Earth’s climate in past geological eras is a difficult task. American scientists have combined models with geological indicators to create a new Phanerozoic temperature curve. The graph agrees well with previously identified periods of glaciation and warming, but contradicts the generally accepted trend of decreasing greenhouse effect.

It is important for climatologists to know the range of average global temperature over a long geologic time span. This helps to better understand the impact of the planet’s past and present climate on other parts of the geosystem (the evolution of extinctions, the chemistry of the atmosphere and oceans).

Usually, paleotemperature graphs are constructed either based on representative data (geological indicators) or with the help of mathematical modeling of the Earth system. An international team led by scientists from the Smithsonian National Museum of Natural History and the University of Arizona (USA) applied the data assimilation method, which allows combining climate models with geological data.

“This method was originally invented for weather forecasting. But instead of predicting future temperatures, we used it to reconstruct ancient climates,” explained paleoclimatologist Emily Judd, first author of the paper. Science.

The result of their work was the curve of average global temperature: PhanDAIt covers most of the Phanerozoic era, which we still live in. This geological time period saw the emergence of all life on Earth, land colonization, and multiple mass extinctions. It now appears that temperatures have changed much more dramatically over the past 485 million years than previously thought. The new study also confirmed a strong correlation between the amount of carbon dioxide in the atmosphere and temperature.

“If you look at the last few million years, you won’t find anything like what you would expect in 2,100 or 2,500 years. We need to look much deeper into the past, when the world was much warmer. That’s the only way to better understand future climate variability,” said study co-author Scott Wing, a paleobotanist at the Smithsonian Museum.

Scientists found that temperature fluctuations occurred much more sharply during the Phanerozoic, from 11 to 36 degrees Celsius. The warmest periods coincided with rising levels _CO2 .

“This clearly shows that carbon dioxide is the main driver of global temperature on a geological scale. When it is low, the climate cools, when it is high, it warms,” ​​said Jessica Tierney of the University of Arizona, one of the study’s authors.

The study shows that the current average temperature of 15 degrees is much colder than the temperature that dominated most of the Phanerozoic. But greenhouse gas emissions are warming the planet at a faster rate than during the hottest periods in the past. Rapid warming threatens the planet’s species and ecosystems and is causing rapid sea level rise. Previous events of such rapid warming have been accompanied by mass extinctions.