That's going to stir things up. I trust Shakun et al are ready for what's likely to come at them and their institutions after this.
With CO2 tracking so close to temperature over such a long period it's hard to imagine anyone challenging the idea...... oops!, except for the deniers, politicians and anti-science crowd.
It coincides remarkably with
http://www.sciencedaily.com/releases/2012/04/120404133801.htm , also in
Nature, about the PETM and subsequent climate excursions :
That mechanism being permafrost melting in response to Milankovich cycles (" changes in Earth's tilt and orbit").
I wonder if some of the CO2 or methane released in future warming events was from a breakdown of Azolla ferns that covered the Arctic Ocean of it they would have just sunk and trapped CO2?
""Basically, it looks like the Earth released a gigantic fart of greenhouse gases into the atmosphere - and globally the Earth warmed by about 5C (9F).
"This event is already widely studied over the whole planet - but the one big exception was the Arctic Ocean."
The core revealed that before 55 million years ago, the surface waters of the Arctic Ocean were ice-free and as warm as 18C (64F).
But the sudden increase in greenhouse gases boosted them to a balmy 24C (75F) and the waters suddenly filled with a tropical algae, Apectodinium.
[snip]
The water changed from salty to fresh, and the ocean became covered with a thick layer of freshwater fern, called Azolla.
"We assume from climate models from the early Eocene Period that there was lots of fresh water coming into the basin via precipitation and giant Canadian and Siberian river run-offs," said Professor Brinkhuis.
"And, at a certain point, this gave rise to this whopping great growth of Azolla."
He believes the prolific growth of this fern, may be linked to the later drops in temperature in the area.
"When you have so much of this plant in this giant sea, you have a mechanism to pump out carbon dioxide from the atmosphere. It is sort of an anti-greenhouse effect," he said.
"We argue that this sits right on the break from the really warm hot house period into the time when the ice house begins."
http://news.bbc.co.uk/2/hi/science/nature/5034026.stm
(2006)
I wonder how much organic matter that was and what happened to it? I seem to remember reading that in some cores the ferns were 3 feet thick.