The Eocene in Antarctica

I’ve just become aware of what I think is a very interesting paper, albeit one from outside of my field: Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch (Pross et al 2012).

The executive summary, as it were, is that Eocene-era Antarctica (55-48 million years ago) may have been a lot warmer than is generally reckoned. It’s been known for quite a while that the southern-polar continent hasn’t always been glaciated, and certainly has been forested in the distant past. However, the impression I’d got (from what I’ve read, here and there) was that the general opinion was that non-glaciated Antarctica was still a fairly cold place. Intuitively, given its extreme latitude, that would seem to make sense.

This study is arguing that simple intuition is wrong in this case.

In fact they’ve found preserved pollens from types of plants that only grow in comparatively-mild temperatures, of at least 8°C. Also, it appears that these milder temperatures must have endured *all year round*, as apparently the types of vegetation in question are badly-damaged by even brief frosts, and so if such frosts were a regular event, the plants in question would quickly vanish from the geological record.

It’s also interesting in respect of possible models for the long-term effects of current-day climate change. The ultimate cause of these warmer Eocene temperatures was enhanced levels of carbon dioxide in the atmosphere, and it seems to have resulted in more-or-less tropical temperatures across most of the planet. This state of affairs also seems to have persisted for millions of years, which sounds like it’s suggesting that the planetary hothouse wasn’t a horribly-unstable condition. Since this was associated with atmospheric CO2 levels of more than twice what they are now, then it might possibly serve as a limiting case on what we can expect from modern-day, human-induced climate change.

This is actually rather good news, at least to those of us who occasionally lose sleep over the possibility of the Venus scenario. (Personal nightmare scenario: this is the real reason for the Fermi Paradox. Terrestrial climates are too pencil-on-end-type unstable, and usually either go iceball or runaway greenhouse long before anything intelligent has had time to evolve. The only reason the Earth hasn’t Venused out already is sheer blind luck…) A ‘tropical’ planet would certainly be uncomfortable and would have many downsides (tropical diseases everywhere?), but human adaptation to such conditions is imaginable; we are technically a tropical animal, I suppose.

So as an antidote to my usual state of mild climate-paranoia, this has certainly been welcome!


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