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There is a controversy over the matter of runaway warming. I'm not talking about limited feedback effects but long term warming produced by a cycle of warming producing warming continuously. I'm inclined to believe it doesn't exist, at least within the sphere of life on earth. I simply don't know of any past examples and it appears that most climate scientists and the IPCC are inclined to agree. The PETM is often offered as an example of runaway warming but this wikipedia article on it doesn't mention runaway warming as a phenomena associated with it.

http://en.wikipedia.org/wiki/Paleocene% ... al_Maximum

But I could be wrong. Here's a graph showing temperature going back 65 million years. Point out to me where runaway warming shows up.

http://jonova.s3.amazonaws.com/graphs/l ... ge_Rev.jpg

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"geologically brief (<200,000 year) events"!! I would say we can get it down to a lot less than that and still call it geologically brief. I don't consider 200K years or even 100K years as being geologically brief, except on the macro scale, I suppose.
From SKS and Wunderground, the heat buildup and GHG increase is 10 to 40 times the rate that led to PETM, and the ocean acidification rate is beyond that ever seen in the geology of Earth. This indicates very strongly that a very long term change will occur with a worse than the worst ELE outcome and longest recovery, if ever.
It is not exactly known just how much sequestered carbon there is, but I have read from 100 to over 1000 times what humans have put out with fossil fuels and overpopulation's slash and burn recklessness. Hansen guaranteed runaway IF all the fossil fuel is burned. Half is gone so we are still looking at only 1/50th to 1/500th of the sequestered carbon. It doesn't seem that it could initiate the positive feedback loop that has been forming since 2009, but it has. The methane blowholes were a wake up call to the world, yet what could happen is scoffed at and efforts to lower HGHGs have been fruitless as time runs to either out now or out in 2024 or max out in 2030.
The oceanic releases of CH4 have been much more and sooner than thought, and the Arctic was up to 9*C warmer than record in 2014. The tundra releases have also gone geometric but are still less than oceanic. This will NOT be the case in a decade when they are both much inflated.
I think many scientists just do not want to look at runaway or even a worse than PETM ELE. Like the IPCC it is political to keep their jobs and not be pessimistic, but overblown conservative instead. People in the know realize that 2*C is too much by 2/10ths of a degree. Most think we will hit +4*C by 2050 or 2100, depending on just how optimistic they are. 1.8*C or higher is all that is needed to set up thermal max by methane turnover.
Whether it stops at some point of warming or just keeps on with increasing depths warmed to release, on land and on sea. Some think that open ocean warming is the initial tipping point and we are past it stopping already.
Yes, 1000 times the carbon released so far IS enough for the Venus Effect. Will it have enough momentum to go all the way? Who really cares when an ELE worse than the Permian is in store?
Will any of the events happen that could stop it??????????
http://www.ranker.com/list/the-world_s- ... ise.dubner

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"With every decision, think seven generations ahead of the consequences of your actions" Ute rule of life.
“We do not inherit the earth from our ancestors; we borrow it from our children”― Chief Seattle
“Those Who Have the Privilege to Know Have the Duty to Act”…Albert Einstein

_________________
With friends like Guido, you will not have enemies for long.

“Intellect is invisible to the man who has none”
Arthur Schopenhauer

"The difference between genius and stupidity is that genius has its limits."
Albert Einstein

I guess that by runaway, you mean completion of a positive feedback loop like the 4 tipping points. Many think that the open ocean tipping point is passed and will lead to tundra and oceanic methane self release, followed by CO2 release.
I certainly hope we have time to prevent the other tipping points from being completed.
Once something can not be changed by human action and is basically controlled by the laws of nature, it is in 'runaway'. When we look at sequestered carbon, this has been less in past thermal max episodes of PETM (30% ELE 30MY recovery)and the Permian Great Dying(95% ELE and 50MY recovery). Then it also apparently did not release all the sequestered carbon but stopped at less. Estimated 70% from some(Permian, PETM less).
This 'episode' could do the same. Still not a rosy thought.
Runaway to 100% or some point below is probably the runaway called 'the Venus Effect'.
Baked and boiled to no life possible. Ever.
Or a worse than Permian ELE, with recovery in the many millions of years.
Recovery from AGW in 400 years if people reduce emissions enough in time. Somehow, some way, natural, artificial, or Divine. I guess many of us will see it first hand, whatever happens.
As reported before, previous hyper-thermals(not thermal maxes) stopped short of runaway at 1.5* C warming (global heat average). Do not depend on the IPCC or wiki.

"2014 was one of the warmest years on record for America’s wintriest state. It was also the warmest for the Bering Sea and Anchorage’s warmest since 1926. In fact, for the first time in recorded history, the temperature never dropped below zero in Anchorage for a whole calendar year.

So with skis stuck in closets and White Christmas dreams dashed (see video above), Alaskans have more reason than ever to pay attention to climate change. From the LA Times:

“To me, the fact that Anchorage won’t dip below zero degrees in calendar year 2014 is just one more signal — as if we needed another one — of a rapidly changing climate,” said Andrew Hartsig, director of the Ocean Conservancy’s Arctic program.

Hartsig said Anchorage’s comparatively balmy weather is consistent with other long-term trends, including diminishing summer sea ice and increasing sea surface temperatures.

“These are definitely red flags that are very consistent with climate change,” said Chris Krenz, senior scientist at Oceana, an international conservation group. “These are anomalies … that show our climate system is off-kilter.”"
http://grist.org/news/anchorage-alaska- ... gn=climate

_________________
"With every decision, think seven generations ahead of the consequences of your actions" Ute rule of life.
“We do not inherit the earth from our ancestors; we borrow it from our children”― Chief Seattle
“Those Who Have the Privilege to Know Have the Duty to Act”…Albert Einstein

This is the opposite way to go, and that is the fatal trajectory;
Aviation Industry Set to Triple Its Global Greenhouse Gas Emissions by 2050
Valerie Brown, Climate News Network | January 3, 2015 11:23 am | Comments

"If commercial aviation were a country, it would rank seventh in global greenhouse gas emissions according to a recent report by the International Council on Clean Transportation (ICCT)."
http://ecowatch.com/2015/01/03/aviation ... c-85901709

Then think about all the military emissions, probably equal. ALL WHEN WE NEED TO CUT EMISSIONS 90% in 9 YEARS!!!!
I believe they are insane. Might as well go off the cliff faster?

_________________
"With every decision, think seven generations ahead of the consequences of your actions" Ute rule of life.
“We do not inherit the earth from our ancestors; we borrow it from our children”― Chief Seattle
“Those Who Have the Privilege to Know Have the Duty to Act”…Albert Einstein

_________________
With friends like Guido, you will not have enemies for long.

“Intellect is invisible to the man who has none”
Arthur Schopenhauer

"The difference between genius and stupidity is that genius has its limits."
Albert Einstein

_________________
With friends like Guido, you will not have enemies for long.

“Intellect is invisible to the man who has none”
Arthur Schopenhauer

"The difference between genius and stupidity is that genius has its limits."
Albert Einstein

This example gives the reference to the range of definitions as indicated by the person mentioned, along with the specific defintion being used in this case. A common tactic is to change said definition and claim an error as a result. There is no way to refute such a claim to the satisfaction of the ones seeking the error so they claim a "win" in the discussion and we all come out worse in the long run.

http://www.climateemergencyinstitute.com/runaway.html

James Hansen says "Runaway greenhouse effect" has several meanings ranging from, at the low end, global warming sufficient to induce out-of-control amplifying feedbacks such as ice sheet disintegration and melting of methane hydrates, to, at the high end, a Venus-like hothouse with crustal carbon baked into the atmosphere and surface temperature of several hundred degrees. Between these extremes is the "moist greenhouse", which occurs if the climate forcing is large enough to make H2O a major atmospheric constituent (Kasting, 1988). In principle, an extreme moist greenhouse might cause an instability with water vapor preventing radiation to space of all absorbed solar energy, resulting in very high surface temperature and evaporation of the ocean (Ingersoll, 1969). Our simulations indicate that no plausible human-made greenhouse gas forcing can cause an instability and runaway greenhouse effect as defined by Ingersoll (1969), Sept 201​​ Climate Sensitivity, Sea Level, and Atmospheric CO2.

​​The runaway climate change that we're talking about result from multiple Arctic positive feedbacks. We are talking about methane which is 72 times more powerful as a global warming greenhouse gas than CO2 over a 20 period. In the case a large sustained methane emission from the Arctic the methane has 100 times the effect of CO2 over a 10 year time frame.

The runaway Arctic +ve feedbacks​​​​​​​​​​​​​​

Loss of Arctic snow and summer sea ice cooling albedo

​Methane emissions from warming sub Arctic peat rich wetlands

​Methane and carbon dioxide emissions and from thawing permafrost

Nitrous oxide emissions from thawing permafrost

Methane emissions from sub sea floor frozen solid methane gas hydrate

​​Each one of these is a powerful positive feedback in increasing the rate of global warming, as well as of course Arctic warming.

Because they all occur in the same region of the Arctic, they will each reinforce all the others, a domino effect called cascading feedbacks.

The Arctic warms more rapidly than the rest of the planet. (Arctic polar amplification)​​.

The Arctic summer sea ice is collapsing past its tipping since 2007. ​​

The rapidly warming Arctic is already emitting methane from all the above sources.​​ As global warming is committed to increase and Arctic warming increases faster, we are now in a runaway planetary emergency situation.

_________________
With friends like Guido, you will not have enemies for long.

“Intellect is invisible to the man who has none”
Arthur Schopenhauer

"The difference between genius and stupidity is that genius has its limits."
Albert Einstein

In the afore mentioned example, should we stop all emission of previously sequestered carbon, there would probably be no significant effect on the methane release unless other factors to lower the temperature were to occur and thus the self generating effect of the "runaway". If it were probable that a reduction of carbon emission now would prevent the continued methane release and the resulting cascade effect this would not be a "runaway" situation.

_________________
With friends like Guido, you will not have enemies for long.

“Intellect is invisible to the man who has none”
Arthur Schopenhauer

"The difference between genius and stupidity is that genius has its limits."
Albert Einstein

That was a good post above with all the feedbacks. It is of the view that we are already in runaway and too late to stop even with a 90% of 1998 reduction in HGHGs by 2024. Of course others have the fantasy that we have until mid century to do that.

Global Warming Caused Mass Extinction 55 Million Years Ago, Shows Study
http://www.webpronews.com/global-warmin ... dy-2014-10

So the dead zones increase to the entire oceans, before they get boiled away.

It looks like the 350.org extrapolation of 8 years left to the ~94% HGHG reduction is also a fantasy, and unachievable by humanity anyway. It is merely academic to guess what percentage of 'turnover' we get. Worse than PETM or the Permian Great Dying, to 'baked Earth'? We know it is happening much faster, by many times over....much faster than people can grasp, and no adaptation that will save anything.
The human population crash precedes permanent ruin of the biosphere.
Seeing that is the worst thing that can happen, there is good reason to try to blow Yellowstone ASAP and just possibly stop the runaway. I have heard we should include Toba to get the Southern Hemisphere to get total global cooling for enough time.

_________________
"With every decision, think seven generations ahead of the consequences of your actions" Ute rule of life.
“We do not inherit the earth from our ancestors; we borrow it from our children”― Chief Seattle
“Those Who Have the Privilege to Know Have the Duty to Act”…Albert Einstein

So let's try James Hansen's accessible definition for runaway warming since the Venus effect is not in the cards, "global warming sufficient to induce out-of-control amplifying feedbacks".

Give me scientifically established specific examples of "out-of-control amplifying feedbacks" as opposed to the normal feedback leading to equilibrium process. What I'm not getting is this "out-of-control" business.