Higher CO2 levels could bring us back to the tropical climate of the Paleogene period

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A new study led by British researchers from Bristol University suggests that unless we reduce the current levels of carbon dioxide emissions, Western Europe and New Zealand could find themselves back in the hot tropical climate of the beginning of the Paleogene period (48 to 56 million years ago).

The early Paleogene is a period of great interest for climatologists, in the sense that the levels of carbon dioxide at the time were similar to those predicted for the end of this century. This is what is explained by David Naafs of the School of Earth Sciences in Bristol University, and author of the study published in  Nature Geoscience: “We know that the early Paleogene was characterized by a greenhouse climate, with elevated levels of carbon dioxide. Most of the existing estimates of temperatures from this period are from the ocean, not the land – what this study attempts to answer is exactly how warm it got on land during this period”

The scientists studied molecular fossils of microorganisms in the ancient peat (lignite) to provide estimations of the earth’s temperature 50 million years ago. It appears that annual ground temperatures in Western Europe and in New Zealand were in reality higher than we previously believed – between 23 and 29°C. This is 10 to 15°C higher than the current average temperatures in these regions. These results suggest that similar temperatures as those of the current heatwave passing over Western Europe and other regions will become the new norm between now and the end of the century, if the levels of CO2 in the atmosphere continue to rise.

For Professor Rich Pancost, co author of the study and director of the Cabot Institute in the University of Bristol, “our work adds to the evidence for a very hot climate under potential end-of-century carbon dioxide levels”, he says. “For example, this and other hot time periods were associated with evidence for arid conditions and extreme rainfall events.”

The research team are now going to look at lower latitude geographical areas. “Did the tropics, for example, become ecological dead zones because temperatures in excess of 40 °C were too high for most forms of life to survive?”, asks David Naafs. “Some climate models suggest this, but we currently lack critical data.”


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