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viach

> These maps are based on emission trends continuing, assuming no political action will be taken.

I think this is a very realistic assumption.

Global Warming Is Irreversible, Study Says:

http://www.npr.org/templates/story/story.php?storyId=9988890...

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I think you misread the comment you responded to (only the first sentence and then you assumed the rest?). He asked the opposite. The question asked about the other direction, up/more, not down/less. Goes to show we should hear one another out...

Irreversible as in "won't fix itself" or in "don't even bother with CO2 extraction [edit: from the atmosphere]"?

The earth goes through cycles (to an extent), so I like to believe that if everyone died, given enough time, the earth would return to its former self. However, I could be wrong.

It seems likely. 500 million years ago, atmospheric CO2 was hundreds of times higher than even the worst projections allow humans to create. CO2 eventually weathers into limestone and gets subducted under continental plates. Ultimately, geological activity renews the balance, and stops us turning into Venus.

NPR article is "irreversible in 1000 years scale". Yes, things are different in million years scale. But even immeidately achieving zero emission today will not cool the planet, at least for 1000 years.

Basically it is irreversible on a human level timescale. Many generations of life on this planet are going to have to adjust to higher average temperatures. It's going to be (and already is really) a mini-extinction event. Unless we don't change course, then it might be a mass extinction.

There's the possibility of geo-engineering.

We can't even agree to stop causing damage. Agreeing to undertake a colossally expensive project to reverse the damage seems like a political impossibility. In 50 or a 100 years maybe, but not in the world as it is today.

General information I've seen is thousands of years for the carbon cycle to return to its preindustrial balance.

Actually, CO2 extraction from the atmosphere may work. But zero emission doesn't. Let me quote from IPCC AR5 SPM E.8 (Climate Change Commitment):

"A large fraction of anthropogenic climate change resulting from CO2 emissions is irreversible on a multi-century to millennial time scale, except in the case of a large net removal of CO2 from the atmosphere over a sustained period. Surface temperatures will remain approximately constant at elevated levels for many centuries after a complete cessation of net anthropogenic CO2 emissions."

This is because most of additional energy (more than 90%) from CO2 forcing is stored in ocean. Oceanic thermal inertia is enough to keep warming in 1000 years scale without any additional CO2.

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