Ancient Earth’s climate wasn’t as hot as we previously thought

New research which is likely to change our ideas about Earth’s climate history have been published by a New Zealand research team in the journal Science.

The study disproves the idea that the eath’s global temperatures were as high as 80°Cprior to about half a billion years ago, with new data indicating that conditions were much milder, ranging from about 2 to 46°C.

The findings have important implications for understanding Earth’s climate system and provide insight into the conditions that allow for the origin and evolution of life.

“This paper provides a robust, multi-billion-year history of Earth’s temperature, offering fascinating insights into the temperature regime prevalent on Earth from its infancy to today,” says Dr Giuseppe Cortese, a principle scientist in paleoclimate at GNS Science, New Zealand, who was not involved in the research.

“The authors describe how this history is shaped by a variety of processes, including the interplay between the evolution of life forms (including plants), sites of formation and alteration of sediments, and a series of feedback loops that either amplify or dampen changes.”

Dr Terry Isson and PhD student Sofia Rauzi from the University of Waikato in New Zealand, used unique data records from various rock types – including shale, iron oxide, carbonate, silica, and phosphate – to chart a consistent ‘map’ of temperature across an enormous portion of geological time.

“By pairing oxygen isotope records from different minerals, we have been able to reconcile a unified history of temperature on Earth that is consistent across all five records, and the oxygen isotopic composition of seawater,” says Isson.

Cortese explains that the study’s findings suggest that before 500 million years ago temperatures on Earth ranged between 2-46°C.

“These conditions are described by the authors as ‘mild’, but that’s just by comparison to previous research that postulated temperatures were, back then, as high as 80°C,” Cortese says.

“The authors propose that changes in clay formation processes, along with other factors, provided a ‘mitigating’ effect that was not fully appreciated.

“The relevance of these findings to the modern climate system is however limited, and I would caution against it being interpreted as a viable way for the Earth to ‘heal itself’, and thus discharge us from any responsibility to mitigate the human-induced warming of the planet that is already underway,” Cortese says.

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