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https://www.sciencealert.com/scientists-warn-the-atmosphere-hasnt-been-like-this-in-14-million-years>
"The last time carbon dioxide in the atmosphere consistently matched today's
human-driven levels was 14 million years ago, according to a large new study
Thursday that paints a grim picture of where Earth's climate is headed.
Published in the journal
Science, the paper covers the period from 66 million
years ago until the present, analyzing biological and geochemical signatures
from the deep past to reconstruct the historic CO2 record with greater
precision than ever before.
"It really brings it home to us that what we are doing is very, very unusual in
Earth's history," lead author Baerbel Hoenisch of the Columbia Climate School's
Lamont-Doherty Earth Observatory told AFP.
Among other things, the new analysis finds the last time the air contained 420
parts per million (ppm) of carbon dioxide was between 14-16 million years ago,
when there was no ice in Greenland and the ancestors of humans were just
transitioning from forests to grasslands.
That is far further back in time than the 3-5 million years that prior analyses
have indicated.
Until the late 1700s, atmospheric carbon dioxide was about 280 ppm, meaning
humans have already caused an increase of about 50 percent of the greenhouse
gas, which traps heat in the atmosphere and has warmed the planet by 1.2
degrees Celsius compared to before industrialization.
"What's important is that
Homo, our species, has only evolved 3 million years
ago," said Hoenisch.
"And so our civilization is tuned to sea level as it is today, to having warm
tropics and cool poles and temperate regions that have a lot of rainfall."
If global CO2 emissions continue to rise we could reach between 600 - 800 ppm
by the year 2100.
Those levels were last seen during the Eocene, 30-40 million years ago, before
Antarctica was covered in ice and when the world's flora and fauna looked
vastly different – for example huge insects still roamed the Earth."
Via Rixty Dixet.
Cheers,
*** Xanni ***
--
mailto:xanni@xanadu.net Andrew Pam
http://xanadu.com.au/ Chief Scientist, Xanadu
https://glasswings.com.au/ Partner, Glass Wings
https://sericyb.com.au/ Manager, Serious Cybernetics
