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Originally Posted by NeilBlanchard
We know that as carbon was naturally deposited in the ground and on the sea floor, from erosion and by plants, and when the level of carbon dioxide dropped to around 450PPM, Antarctica started to freeze up.
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Well yes, but what makes you think that's the way it should stay ?
Because it's convenient for mankind ?
Earth isn't bothered about mankind, it was there, continuously changing, long before we even existed, and it will still be there long after we've gone the way of the dinos.
Species have gone extinct, as a matter of fact most (99+ %) of the species that once lived on earth have long been extinct - but others have appeared.
Should we be alarmed when we see the same happening now ?
What makes you think all this is going to stop because it'd be so mighty convenient for us ?
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Then, around 1850 we started burning coal in quantity, and a little later oil and gas.
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You seem to forget we've been burning wood for ages and ages before that, and definitely none of that came from careful sustainable forest management ...
When we started farming, we simply burned down the forest to clear it and put nutrients into the soil.
When we moved to new pastures, we burned down a new clearing further down the road.
Nature's been doing the same.
Lightning and fire have taken out huge areas of forest as there was no-one to fight the fires.
At worst, we've triggered a somewhat quicker return to the very long periods (millions, rather than thousands of years) of warmer conditions before the current cycles of ice ages and temporary milder periods of the late Pleistocene.
If you look beyond the time scale of the Vostok ice core data (500,000 years) to a period of 500,000,000 years, we were already heading for a warmer environment in the very long run.
We're in the 4th temperature dip (and only the 2nd CO2 dip) since the Cambrian period.
CO2 levels are again at what is an unusually low level for planet Earth, but seen before during Perm.
And what's more, there no longer appears to be any relation at all between temperature and CO2 on this timescale.
Around midway during the Jurassic period, CO2 shot up wildly, but temperature didn't follow.
Late in the Jurasic era, the comet hit the Yucatan and temps plunged while CO2 decreased a bit, but stayed rather high.
In the Cretaceous, the temperature shot up again and stayed high, despite CO2 levels continuously dropping to their present day lows !
Temperatures plunged in the Tertiary period, with Earth remaining cold into the Quaternary.
Hard to tell how long this cold will last, but in a few million or 100 million years, it's bound to get a whole lot hotter around here.
Before that happens, it'll likely get a good deal colder
The ocean level has been unusually low during the latter half of Tertiary period, only to rise sharply, fall again, and rise again, the rise continueing into the Quaternary period, and to this very day.
The ocean has risen, then fallen again.
Should we really be alarmed when we see the same happening now ?
Around 80% of Earth's life has been warm, better get used to it.