

Today’s Antarctic region once as hot as California, Florida - edj
http://news.yale.edu/2014/04/21/today-s-antarctic-region-once-hot-california-florida

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jofer
It's also worth putting this in a bit of geologic perspective. The article
mentions this, but doesn't explain it.

The Eocene is just before the earth went into a period of "icehouse" climate
(that's still going on). During the part of the Eocene this article refers to,
the earth was in a "greenhouse" phase, and global temperatures were much
warmer than they've been any time since.

At that time (and throughout the majority of Earth's history), there likely
weren't any significant ice caps on the planet.

On very long timescales, the Earth goes through periods of icehouse and
greenhouse climates. We're currently in an "interglacial" within a period of
icehouse climate that has persisted since the late Eocene. Most of Earth's
history is dominated by long phases of greenhouse climate. During these, the
global climate is more stable and much warmer. We don't have ice ages, and
there probably aren't any ice caps at the poles.

The last period of icehouse climate began just after this, in the late Eocene.
(Again, the "ice ages" you hear about are glacials and interglacials within a
period of icehouse climate.)

Also, as other folks have mentioned, the Eocene is relatively recent, and
Antarctica was essentially in its present-day position (the coals and other
"warm-weather" rocks in Antarctica date from much earlier when it was near the
equator).

Regardless, it is quite interesting that sea surface temperatures were as warm
as this evidence shows! I just wanted to put this into a bit of perspective.

*Caveat to all of this: I'm a geologist and not a climatologist.

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sologoub
That's exactly the detail missing from this article!

The other bit of information that I would really find useful as a lay person
is how temperature distribution varied during the "greenhouse" climates. For
example, was it linear to todays differential, implying that if I can directly
apply an increase of 20C to today's temp and say that the avg. CA temp would
be 34C from the 14C referenced currently or is it more even and the jump at
extremes will be significantly larger or smaller than at equator?

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jofer
It's probably very spatially variable, but beyond that, I'm out of my depth.

Ocean circulation plays a large role in regional (and global) variations in
climate. If nothing else, the changes in the shape of the ocean basins over
time would result in very different regional climate patterns, even if the
average global temperature stayed the same.

On top of that, changes in average global temperature tend to vary strongly by
latitude, if I remember correctly.

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dragop
In the current ice age, the cycle between glacials and inter-glacials is
primarily driven by variations in the Earth's orbit, and therefore the
distribution of incoming solar radiation over the Earth's surface by season
and latitude. Obviously, as you mention, this then interacts with global
climate through atmospheric and ocean circulation. They're called Milankovitch
cycles after Milutin Milanković, who calculated them all (by hand!) at the
beginning of the 20th century.

Obviously orbital forcing would exist in "greenhouse" times, to answer the
parent comment.

If you are interested, there are three variations:

\- eccentricity, change in the ellipticity of the orbit around the Sun, ie how
close to a circular orbit it is. So if it's close to circular, temperature
variations by season will be low. If it's more eccentric, you will get greater
variation by season.

\- tilt of the axis of rotation, which varies around 22-24 degrees. So when
the Earth is tilted over more, at the poles it will be hotter when facing the
Sun, colder when facing away.

\- axial precession, which is the wobble of the axis of rotation, a bit like
if you put a toy gyroscope on a table. This has a latitudinal and seasonal
effect, particularly at the poles.

These cycles are approximately 100, 41 an 25 thousand years respectively. Put
them together and the periods very closely follow the current ice age climate
variations.

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synctext
PNAS paper:
[http://www.pnas.org/content/early/2014/04/16/1321441111.abst...](http://www.pnas.org/content/early/2014/04/16/1321441111.abstract?sid=416fb7a8-dbf3-43d0-9dba-8b4bbcf0c1a0)

Yale promo: temperatures in parts of Antarctica reached as high as 17 degrees
Celsius (63F) during the Eocene, with an average of 14 degrees Celsius (57F) —
similar to the average annual temperature off the coast of California today.

PNAS abstract: Here, we present multiproxy data from Seymour Island, near the
Antarctic Peninsula, that provides well-constrained evidence for annual SSTs
of 10–17 °C (1σ SD) during the middle and late Eocene.

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JoeAltmaier
Where was Antarctica during the Eocene? Was it then parked over the South
Pole?

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tokenadult
A Google search "Eocene epoch continents" brings up pages suggesting
Antarctica's location then was similar to its location now. Thank you for
asking that interesting question, as I remembered that in earlier deep
geologic time, Antarctica was much nearer to the equator.

~~~
edj
It sounds like Australia's geographical relationship to Antarctica at the
beginning of the Eocene contributed to Antarctica's temperate climate at the
time. From Wikipedia[1}:

 _At the beginning of the period, Australia and Antarctica remained connected,
and warm equatorial currents mixed with colder Antarctic waters, distributing
the heat around the planet and keeping global temperatures high, but when
Australia split from the southern continent around 45 Ma, the warm equatorial
currents were routed away from Antarctica. An isolated cold water channel
developed between the two continents. The Antarctic region cooled down, and
the ocean surrounding Antarctica began to freeze, sending cold water and
icefloes north, reinforcing the cooling._

1:
[https://en.wikipedia.org/wiki/Eocene#Palaeogeography](https://en.wikipedia.org/wiki/Eocene#Palaeogeography)

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cmsmith
Missing from this press release, though not from the journal paper, is the
unstable effect of ocean currents on water temperatures. The fact that the
oceans have a straight shot around Antarctica at the moment generates a huge
ocean current which blocks water from warmer latitudes making it south.
Antarctica and South America were connected as recently as 30 MYa, blocking
the circumpolar current and allowing water in the southern oceans to be much
more mixed.

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frandroid
Why do they say "today's" Antarctic region? That just makes the whole headline
confusing. The Antarctic was probably in the same location then, so let's just
remove the word Today, and now it's way clearer.

Come on, give me that bloody headline writing job already!!

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NAFV_P
I was thinking that hurricane type storms would have been even worse 50m years
ago.

