[guide.chat] news palm trees grew on antartica
- From: vanessa <qwerty1234567a@xxxxxxxxx>
- To: "GUIDE CHAT" <guide.chat@xxxxxxxxxxxxx>
- Date: Thu, 2 Aug 2012 00:11:41 +0100
Palm trees 'grew on Antarctica'
By Jason Palmer
Science and technology reporter, BBC News
The study also found relatives of modern trees such as the baobab and macadamia
North Pole 'was once subtropical'
Crater focus for drilling plans
Tiny fossils reveal ice history
Scientists drilling deep into the edge of modern Antarctica have pulled up
proof that palm trees once grew there.
Analyses of pollen and spores and the remains of tiny creatures have given a
climatic picture of the early Eocene period, about 53 million years ago.
The study in Nature suggests Antarctic winter temperatures exceeded 10C, while
summers may have reached 25C.
Better knowledge of past "greenhouse" conditions will enhance guesses about the
effects of increasing CO2 today.
The early Eocene - often referred to as the Eocene greenhouse - has been a
subject of increasing interest in recent years as a "warm analogue" of the
current Earth.
"There are two ways of looking at where we're going in the future," said a
co-author of the study, James Bendle of the University of Glasgow.
"One is using physics-based climate models; but increasingly we're using this
'back to the future' approach where we look through periods in the geological
past that are similar to where we may be going in 10 years, or 20, or several
hundred," he told BBC News.
The early Eocene was a period of atmospheric CO2 concentrations higher than the
current 390 parts per million (ppm )- reaching at least 600ppm and possibly far
higher.
Global temperatures were on the order of 5C higher, and there was no sharp
divide in temperature between the poles and the equator.
Frozen thermometers
Drilling research carried out in recent years showed that the Arctic must have
had a subtropical climate.
But the Antarctic presents a difficult challenge. Glaciation 34 million years
ago wiped out much of the sediment that would give clues to past climate, and
left kilometres of ice on top of what remains.
Archaea hold on to their structure through millions of years, giving hints of
long-gone temperatures
Now, the Integrated Ocean Drilling Program (IODP) has literally got to the
bottom of what the Eocene Antarctic was like, dropping a drilling rig through
4km of water off Wilkes Land on Antarctica's eastern coast.
The rig then drilled through 1km of sediment to return samples from the Eocene.
With the sediment came pollen grains from palm trees and relatives of the
modern baobab and macadamia.
Crucially, they contained also the remnants of tiny single-celled organisms
called Archaea.
The creatures' cell walls show subtle molecular changes that depend on the
temperature of the soil surrounding them when they were alive. The structures
are faithfully preserved after they die.
They are, in essence, tiny buried thermometers from 53 million years ago.
Together, the data suggest that even in the darkest period of Antarctic winter,
the temperature did not drop below 10C; and summer daytime temperatures were in
the 20Cs.
The lowland coastal region sported palm trees, while slightly inland, hills
were populated with beech trees and conifers.
Dr Bendle said that as an analogue of modern Earth, the Eocene represents
heightened levels of CO2 that will not be reached any time soon, and may not be
reached at all if CO2 emissions abate.
However, he said the results from the Eocene could help to shore up the
computer models that are being used to estimate how sensitive climate is to the
emissions that will certainly rise in the nearer term.
"It's a clearer picture we get of warm analogues through geological time," he
said.
"The more we get that information, the more it seems that the models we're
using now are not overestimating the [climatic] change over the next few
centuries, and they may be underestimating it. That's the essential message."
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