As a Nature article, I assume it is paywalled, and I’ll not pay. As Willis says, “There has to be a better way to do science.” But how do they account for their assertions on the basins being different and the circulations being so significantly different? According to Dr. Scotese, this is the way the earth looked 14 Mya: http://www.scotese.com/miocene.htm . The only difference I can see is substantially higher sea level. I notice the caption for the global map indicates it would have been about the same as today starting about 20 Mya. I notice he stipulates “Antarctica was covered by ice and the northern continents were cooling rapidly.” I assume rapid means a half-dozen degrees C over about 15 million years.

How can LaRiviere et al justify claims of such magnitude over such minute differences? It seems silly at best. Primary global circulation has always been considered key to an ice-free earth. Obviously that is impossible, even with the straights (where we now have canals) somewhat open. Of course, my understanding of premodern continental configuration and circumglobal ocean circulation can be flawed and outdated, and the base theory may be wrong, but they are asserting that the ocean was different with no apparent means whereby it might have been. Dr. Scotese suggests sea level and relative land area (and especially ice) are important factors in long-term climate change. I suppose, but the effect cannot be dominant, or we would have never gotten this cold in the first place. http://www.scotese.com/moreinfo15.htm (I suppose I should allow that something may have changed to start the cooling and increasing land and ice keep causing cooling, but then why did we stop? Why have we only gotten this cold? Our current ice age is already over 2 million years running. Why have we stalled at 285 K? Why didn’t we go down to 283 K as we did many millions of years ago? Why didn’t we go even colder? Whatever it is, it sure seems a stretch to attribute significance to CO2!

Watts Up With That?

Press Release 12-107
Today’s Climate More Sensitive to Carbon Dioxide Than in Past 12 Million Years

Geologic record shows evolution in Earth’s climate system

Image of the phytoplankton Emiliania huxleyi.
The phytoplankton Emiliania huxleyi offers clues about climate past, present and future.
Credit and Larger Version

Until now, studies of Earth’s climate have documented a strong correlation between global climate and atmospheric carbon dioxide; that is, during warm periods, high concentrations of CO2 persist, while colder times correspond to relatively low levels.

However, in this week’s issue of the journal Nature, paleoclimate researchers reveal that about 12-5 million years ago climate was decoupled from atmospheric carbon dioxide concentrations. New evidence of this comes from deep-sea sediment cores dated to the late Miocene period of Earth’s history.

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