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Old 08-28-2019, 05:30 PM   #6654 (permalink)
aerohead
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Sahara

Quote:
Originally Posted by freebeard View Post
So what you're saying is...

Anthopogenic forcing is the only thing staving off an Ice Age?

Here's you're climate change right here. The Sahara Desert was created in as little as 100 years six thousand years ago:

Milankovitch cycles or what?
No kiddin'!
There was a methane dip and flourine spike around 6400 BC,with a large,abrupt hydrological change in the tropics.And apparently,the tropics drive climate change.They've driven all four of the last ice ages.
The African Humid Period ended around 3,000 BC,entering into perpetual drought which extends to today.
All interglacials and glacials have been driven by precession of the equinox,superimposed on the 100,000-year,Milankovitch orbital eccentricity cycle,when the solstice occurred during perihelion.It's a inverse-square law effect.
There's also a 1,500-year cycle which rides along which also has to do with insolation,although that's a missing puzzle piece for me so far.
Coolings trend slowly,while warmings can be extremely abrupt,so your 100-year value seems very plausible.I don't have that data point.
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The Younger Dryas ended precisely 11,640-years ago.Between then and 11,000-years ago,the Wisconsinan/W'u'rm glacial had ended,beginning the Holocene.
The Last Glacial Maximum was at 18,000-years ago.On average,we wouldn't expect to be in a new glacial maximum for another 82,000-years.
Sea-level and temperature was steady until 1880,as we moved into the Anthropocene,and geologically,it's unprecedented.What we've done to the environment has never happened before.
We could see an additional 10-F by 2100,and 80-feet of sea-level rise.It's happened before and that's why our greenhouse gases are freaking out the climatologists.
As to staving off an ice age,I'm not qualified to take that on.All we know is,that the last time there was this much greenhouse gas in the atmosphere,Earth was this warm and the oceans were a lot higher.
Someone has said that a 2-degree warming will end the ice sheets.But they don't say whether its 2F or 2C.The 'climate sensitivity' of Earth is 2.7-C (4.8-F) for a 560ppmv 'doubling' of carbon dioxide,or it's equivalent.We're at around 411 ppmv today.
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