More on catastrophic climate change

monty

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#2
Yup, scary stuff. I've become irritated at how people use the term "tipping point," though... a recent bunch of press has started using it to mean "if we stop increasing our anual CO2 production now, we won't stop or reverse global warming," which, while true, is more because the climate effects are caused by the amount that's currently there, not the amount that we add every year, so this is not new or particularly deep. Maybe I should be OK with the phrase, because at least it gets the attention of people who don't understand what I just described, but it bugs me because there may be something a lot worse in terms of what I call a tipping point: once things get to a certain point, there may be a self-sustaining "runaway" chain reaction.

Several worrisome things could happen if greenhouse gasses and global warming hit a certain threshold: Disolved CO2 in the oceans could be released to the air as the water temperature goes up, increasing the atmospheric greenhouse gasses further, raising the temperature more, releasing more CO2, ad infinitum. Also, as the glaciers shrink, there is less sunlight reflected by the white snow, and more absorbed by the dark ground and water, so the amount the planet is heated by the sun goes up.

Of course, there may be mitigating effects as well as accelerating effects-- unfortunately, we don't really understand (for example, more desert, different cloud cover, ...) However, if we hit a "tipping point" where we're in a vicious circle, we're in big trouble, much more so than the kind of "tipping point" they're talking about in the news a lot.
 

DHyslop

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#3
monty said:
Several worrisome things could happen if greenhouse gasses and global warming hit a certain threshold: Disolved CO2 in the oceans could be released to the air as the water temperature goes up, increasing the atmospheric greenhouse gasses further, raising the temperature more, releasing more CO2, ad infinitum. Also, as the glaciers shrink, there is less sunlight reflected by the white snow, and more absorbed by the dark ground and water, so the amount the planet is heated by the sun goes up.
More worrisome IMO are methane hydrates, which are stable only in a narrow P/T zone below the seafloor. If the oceans warm up substantially some of these hydrates could melt and make their way into the ocean/atmosphere system. Methane itself is another big fun greenhouse gas, but it would probably oxidize quickly in the atmosphere.

This particular model is purely theoretical and has been invoked for the rapid warming at the Paleocene/Eocene Thermal Maximum (an interesting hypothesis, albeit one that is untestable from what I've read).

Dan
 

main_board

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#4
I saw a documentary on an airplane that said instead of global warming, we should be worried about global cooling. Apparently, there is a reliable trend in the past that as CO2 emmissions increased and the temperature appeared to increase, it suddenly brought on a great cooling, similar to an ice age. The evidence they presented appeared strong and valid. Definitely took me by surprise. Just some more food for thought.

Cheers!
 

Euprymna

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#5
main_board said:
I saw a documentary on an airplane that said instead of global warming, we should be worried about global cooling. Apparently, there is a reliable trend in the past that as CO2 emmissions increased and the temperature appeared to increase, it suddenly brought on a great cooling, similar to an ice age. The evidence they presented appeared strong and valid. Definitely took me by surprise. Just some more food for thought.

Cheers!
Great cooling of parts of the planet will be the result of initial global warming!

It's a succession of events that may appear contridactory...i.e. starts as an increase in temperature but may cause an iceage!
First melting icesheets will greatly reduce salinity of the water, which will stop this normally cold hypersaline water to sink---the driving factor of the thermohaline circulation the regulator of the climate of europe!

I think the increasing acidity of the oceans due to increased CO2 imight be more worrying...at least for our mollusc friends...let's see

eups
 

CapnNemo

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#6
It all does not bode well!

I remember reading a fascinating book called Mapping the Deep which was the story of Ocean Science. A scientist in there suggested we could stave off Global Warming (I think) by feeding iron to Plankton or something, but unfortunately it might trigger an ice age.

The Independent, a UK newspaper that Sorseress linked to at the beginning of this thread seems often to be alone in running front page headlines on Global Warming. I have to look at the papers every day as part of my job and it's incredibly frustrating to see only the Independent with a front page on GW and then the Times or the Telegraph rolling with some guff about Prince Charles or some other rubbish.
 

Euprymna

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#7
CapnNemo said:
It all does not bode well!

I remember reading a fascinating book called Mapping the Deep which was the story of Ocean Science. A scientist in there suggested we could stave off Global Warming (I think) by feeding iron to Plankton or something, but unfortunately it might trigger an ice age.
Yeah, read this book too! Very nice read!
This guy (don't remember his name) was saying that iron was the only element that phytoplankton was lacking in the southern ocean and adding tons of it would be enough to create an enormous bloom enough to suck up all the excess CO2! Crazy thing to experiment...but like the author was saying, we are allready experimenting the effect of adding enormous amounts of CO2 in the atmosphere so why not add some iron?

eups
 

sorseress

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#8
Euprymna said:
Great cooling of parts of the planet will be the result of initial global warming!

It's a succession of events that may appear contridactory...i.e. starts as an increase in temperature but may cause an iceage!
First melting icesheets will greatly reduce salinity of the water, which will stop this normally cold hypersaline water to sink---the driving factor of the thermohaline circulation the regulator of the climate of europe!

I think the increasing acidity of the oceans due to increased CO2 imight be more worrying...at least for our mollusc friends...let's see

eups
There was a study recently that discovered that the number of "thermal sinks"
was seriously reduced with potentially devestating results for northern Europe. This isn't the story I origianlly read, I couldn't find that one, but this explains it pretty well.

http://www.timesonline.co.uk/article/0,,2087-1602579,00.html
 

main_board

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#9
Thats what they were talking about in the doco: The slowing/shutting down of the thermohaline circulation near Europe!

Oh, and the iron thing is a no go. The point of it is to get CO2 locked away in the calcium carbonate shells of plankton which then fall to the bottom of the ocean and get incorperated into sedimentary rock at the bottom of the ocean. However, I read/listened/saw something about that were some sort of experiments had been done where the seeded some parts of the ocean with iron. Unfortunately, the food web/cycles were so efficient that very little CO2 actually made it to the bottom of the ocean, so the scientists concluded that it wasn't a very good method. Too bad!

Cheers!
 

bigGdelta

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#10
DHyslop said:
More worrisome IMO are methane hydrates, which are stable only in a narrow P/T zone below the seafloor. If the oceans warm up substantially some of these hydrates could melt and make their way into the ocean/atmosphere system. Methane itself is another big fun greenhouse gas, but it would probably oxidize quickly in the atmosphere.

This particular model is purely theoretical and has been invoked for the rapid warming at the Paleocene/Eocene Thermal Maximum (an interesting hypothesis, albeit one that is untestable from what I've read).

Dan
I've seen proposals to mine the methane hydrate in the gulf of mexico and elsewhere. Besides disrupting unique ecosystems, a major release of methane from hydrate resevoirs has been called the reason for the permian extinction (98% of all species died but most of y'all already knew that). I think the critical number was 10 degrees IIRC.
 

DHyslop

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#11
I think its a bit of a stretch to apply clathrate release to the P/T extinctions, it just doesn't fit the bill. Since the hypothesis has become so popular for the PETM people are trying to pigeon-hole it everywhere else, too (just like how people were trying to find impact events for every tiny extinction in history).

Mining would be especially difficult. When you're trying to mine a layer that's kilometers below the seabed it might be cheaper just to build the solarsat from the other thread :)

Dan
 

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