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from the couldn't-see-the-wood-for-the-trees^W-ice dept.
https://www.livescience.com/ancient-rainforest-antarctica.html
About 90 million years ago, West Antarctica was home to a thriving temperate rainforest, according to fossil roots, pollen and spores recently discovered there, a new study finds.
The rainforest's remains were discovered under the ice in a sediment core that a team of international researchers collected from a seabed near Pine Island Glacier in West Antarctica in 2017.
As soon as the team saw the core, they knew they had something unusual. The layer that had formed about 90 million years ago was a different color. Back at the lab, the team put the core into a CT (computed tomography) scanner. The resulting digital image showed a dense network of roots throughout the entire soil layer. The dirt also revealed ancient pollen, spores and the remnants of flowering plants from the Cretaceous period.
The sediment core revealed that during the mid-Cretaceous, West Antarctica had a mild climate, with an annual mean air temperature of about 54 F (12 C), similar to that of Seattle. Summer temperatures were warmer, with an average of 66 F (19 C). In rivers and swamps, the water would have reached up to 68 F (20 C).
"Before our study, the general assumption was that the global carbon dioxide concentration in the Cretaceous was roughly 1,000 ppm [parts per million]," study co-researcher Gerrit Lohmann, a climate modeler at Alfred Wegener Institute, said in the statement. "But in our model-based experiments, it took concentration levels of 1,120 to 1,680 ppm to reach the average temperatures back then in the Antarctic."
https://www.nature.com/articles/s41586-020-2148-5
(Score: 2) by Bot on Friday April 03 2020, @06:02PM (2 children)
> But in our model-based experiments
AKA model
My issue with correlating temperature with CO2 is that it assumes you know the energy irradiated by the sun in the past. Has it been desumed, how?
Account abandoned.
(Score: 0) by Anonymous Coward on Friday April 03 2020, @06:51PM
You might find this PDF [arxiv.org] interesting.
(Score: 2) by dry on Saturday April 04 2020, @03:20PM
They have a pretty good idea of how the Sun's output has increased over the years, as it converts hydrogen to helium, it gets denser and produces more heat. You could search for the faint Sun paradox. Of course 90 million years isn't that long compared to the age of the Solar System.
A better question is how dense the atmosphere was at the time? Was the sea level pressure 1 ATM, more, less? Never seen much on that, just ratios of oxygen and CO2 and sometimes methane.