恐龍是被溫室效應凍死的 - 地球科學討論

恐龍是被溫室效應凍死的 2010.04.25 中廣新聞

http://news.chinatimes.com/world/0,5246,50403393x132010042500697,00.html


英國研究人員說，恐龍不是被隕石害死的，而是被溫室效應導致的海水降溫凍死的。

普里矛斯大學研究人員研究了挪威北極圈的恐龍化石以後認定，一億三千七百萬年以
前，地球的二氧化碳大量增加，氣溫升高，北極圈的冰層融化，冰水往南流，海水溫
度一下子降了攝氏九度。恐龍是冷血動物需要環境的溫度讓他們保持體溫。海水溫度
驟降凍死了許多恐龍。

以往科學家認為，恐龍是因為六千五百萬年前，一次巨大的變動而滅絕的。一般認為
地球這次大變動是遭到隕石襲擊而一下子絕種的。但是負責這項研究的普萊斯說，恐
龍應該是因為海水降溫慢慢被凍死的。


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外電原文：http://www.plymouth.ac.uk/pages/view.asp?page=29944

Scientists identify freezing times for Cretaceous dinosaurs

2010.04.15 University of Plymouth


Summary

Scientists studying fossils and minerals from Arctic Svalbard, in Norway,
have discovered evidence that the ‘greenhouse’ climate of the Cretaceous
period was punctuated by a sudden drop in global temperatures.


Further detail

The drop is estimated to have occurred some 137 million years ago during a
time when dinosaurs roamed the Earth, and would have seen the islands fall
from an average of 13 degrees centigrade (ocean temperature) to as low as
four degrees.

The findings, which were published in the journal Geology and featured as a
highlight in Nature Geoscience, will further contribute to the debate over
climate change as they appear to contradict the common model which links
high levels of Carbon Dioxide (CO2) – as recorded in the Cretaceous era –
with reduced polar ice caps.

Despite being located in the Arctic Circle, Svalbard was home to numerous
species of dinosaur and was typically characterised by warm, shallow seas
and swamps.

But the research team, led by Dr Gregory Price of the University of Plymouth,
found evidence in fossils and carbonate materials preserved in marine rocks
in the region of a transient shift to cooler glacial conditions around 137
million years ago.

Dr Price said: "At certain times in the geological past, the world has been
dominated by greenhouse conditions with elevated CO2 levels and warm Polar
Regions, and hence, these are seen as analogues of future global climate.

“But this research suggests that for short periods of time the Earth plunged
back to colder temperatures, which not only poses interesting questions in
terms of how the dinosaurs might have coped, but also over the nature of
climate change itself.”

Dr Price, along with Dr Elizabeth Nunn, of Johannes Gutenburg Universitat
in Mainz, Germany, first visited Svalbard in 2005 to collect fossils and
samples, in an area famed for a number of paleontological discoveries,
including giant marine reptiles such as pliosaurs and icthyosaurs.

The samples were analysed back in Plymouth and prompted return trips to the
area to gather more evidence.

“The flourishing of the dinosaurs and a range of other data indicates that
the Cretaceous period was considerably warmer and boasted a high degree of
CO2 in the atmosphere,” said Dr Price.

“But over a period of a few hundred or a few thousand years, ocean
temperatures fell from an average of 13 degrees centigrade to between eight
and four degrees.

“Although a short episode of cool polar conditions is potentially at odds
with a high CO2 world, our data demonstrates the variability of climate over
long timescales.”


ENDS




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