Runaway global warming, what is the tipping point supposed to be?

[Corsair 115]

Simply, it occurs to me that at various points in the planet's history conditions have been substantially warmer.

But, of course, while it may have been substantially warmer in the past, there were also, it seems to me, some important differences between that past and our present that ought to be factored in. These would be such things as continental position and shape (which would affect ocean currents and weather patterns), and the fact that huge amounts of the Earth's surface have been deforested to make way for human settlements and farmlands.

Due to these differences I wonder how much applicability there is in saying because the Earth millions of years ago was substantially warmer than it is now we don't really need to worry about it.

 

[CapelDodger]

For example; http://www.sciencedaily.com/releases/2008/12/081210133814.htm

Indeed, and only one example amongst many.

 

[mhaze]

Originally Posted by mhaze
How big a metastable temperature range is there before Earth moves to the alternate stable point that exists past the (tipping points, runaway, blah blah blah).
Either degrees C, K, F, or R may be used in the answer.
​

Nobody knows.

We know the kind of event that will constitute a tipping-point. That would include the self-reinforcing melting of permafrost. It may include the permanent loss of summer Arctic sea-ice.

Permafrost is already melting, and at an increasing rate, so that tipping-point has probably already been reached.

Here is a bit of help for you -

There is about 80C difference between pole and equator, a distance of some 8000 miles. So very roughly, climate moves 100 miles per 1C change.

How big a metastable temperature range is there before Earth moves to the alternate stable point that exists past the (tipping points, runaway, blah blah blah). Either degrees C, K, F, or R may be used in the answer.

 

[Zytheran]

Based on paleoclimate records it would appear the maximum temperature increase, regardless of continent placement and solar output is about +10C compared to now. The temperature has been up and down lots but there seems to be level above which it doesn't go. I'd guess this limit is based on distance from the sun and solar output, which is slowly increasing.
I assume that this temperature limit is due to increasing humidity leading to greater cloud production which forms the limit as the albedo drops. At this point of stability we have ended up with a very tropical forested planet. And I'd say it rained like nothing we've ever seen based on calculated levels of erosion and depth of silts in various places around the world.
Someone must have run a climate model to reproduce the paleo climate and work out why it topped out?

 

[GreyICE]

Could anyone fill me in on the model and explanation of runaway global warming? What are the positive feedback cycles that would cause increased temperature? Ice cap loss screwing with albedo, methane release from clathrate deposits, what else? How much difference would negative feedback factors like increased algal activity have? How hard a shove does the system need to go spiralling hard one way or another?


Simply, it occurs to me that at various points in the planet's history conditions have been substantially warmer. How big a metastable temperature range is there before Earth becomes Venus?

Earth cannot become Venus. Impossible.

Global Warming cannot 'run away.' At a certain level CO2 absorption bands become saturated, that'll limit the upper temperature.

There isn't a tipping point.

 

[mhaze]

Based on paleoclimate records it would appear the maximum temperature increase, regardless of continent placement and solar output is about +10C compared to now. The temperature has been up and down lots but there seems to be level above which it doesn't go. I'd guess this limit is based on distance from the sun and solar output, which is slowly increasing.
I assume that this temperature limit is due to increasing humidity leading to greater cloud production which forms the limit as the albedo drops. At this point of stability we have ended up with a very tropical forested planet. And I'd say it rained like nothing we've ever seen based on calculated levels of erosion and depth of silts in various places around the world.
Someone must have run a climate model to reproduce the paleo climate and work out why it topped out?

Good point.

Hotter air has more moisture, which means more "low level rain and snow clouds". Albedo changes occur from both more snow, and increased low level clouds. (negative feedback). Increased IR retention occurs from higher water vapor in the atmosphere (positive feedback).

You have suggested an upper temperature limit irregardless of whether any "runaway or tipping point" phenomena may have or could exist. But the very factors which create this absolute limit to temperature on a water planet should also affect whether "runaway or tipping points" can occur at all. The planet is dominated by negative feedback.

Ill defined but often cited Alarmist concerns about "runaway/tipping points" seem based on a concern that short term positive feedback exists from the current temperature trend. There's a lot of vagueness in whether Alarmists acknowledge longer term fundamental negative feedbacks. They have often quoted temperature increases in excess of 10C as an example.

We are using for the purposes of this discussion the convenient phrase "metastable". Note there is no certainty that the Earth's climate is "metastable" with the exception of the ice age cycles.

 

[GreyICE]

Good point.

Hotter air has more moisture, which means more "low level rain and snow clouds". Albedo changes occur from both more snow, and increased low level clouds. (negative feedback). Increased IR retention occurs from higher water vapor in the atmosphere (positive feedback).

You have suggested an upper temperature limit irregardless of whether any "runaway or tipping point" phenomena may have or could exist. But the very factors which create this absolute limit to temperature on a water planet should also affect whether "runaway or tipping points" can occur at all. The planet is dominated by negative feedback.

Runaway can't happen period, when an upper limit exists on the forcing effect. Positive and negative forcing doesn't matter. You can design an accelerator pedal that increases your car's speed faster as more force is applied, but that doesn't make your car capable of Mach 10, it just means it tends to accelerate more than you think it will.

Of course this might require simple understanding to understand.

Ill defined but often cited Alarmist concerns about "runaway/tipping points" seem based on a concern that short term positive feedback exists from the current temperature trend. There's a lot of vagueness in whether Alarmists acknowledge longer term fundamental negative feedbacks. They have often quoted temperature increases in excess of 10C as an example.

We are using for the purposes of this discussion the convenient phrase "metastable". Note there is no certainty that the Earth's climate is "metastable" with the exception of the ice age cycles.

Ah, good old lie about the feedbacks and create uncertainty.

The 'vagueness' about the feedbacks is in fact well defined. Since you've quoted the relevant sections of the IPCC report, I suppose that understanding simply does not flow from being given access to the information.

 

[lomiller]

Earth cannot become Venus. Impossible.

Global Warming cannot 'run away.' At a certain level CO2 absorption bands become saturated, that'll limit the upper temperature.

There isn't a tipping point.

Not quite. No other source of CO2 approaches what is stored in carbonate rock, and the Earth could become like Venus if it got hot enough for this stuff to break down. That said, this requires a surface temperature some 100+ degrees warmer then current, and there is no known mechanism for that to occur. Even if all the other sources of CO2 were to be released it wouldn’t create enough warming for this to happen.

 

[mhaze]

Ah, good old lie about the feedbacks and create uncertainty. ..... Since you've quoted the relevant sections of the IPCC report, I suppose that understanding simply does not flow from being given access to the information.

The sections of IPCC which affirm the uncertainty in solar and cloud effects
must be all good old lies ...

Otherwise, you deny the IPCC...

A Denier?

 

[lomiller]

The sections of IPCC which affirm the uncertainty in solar and cloud effects
must be all good old lies ...

Otherwise, you deny the IPCC...

A Denier?

It’s still highly unlikely that the uncertainty in cloud formation would work to prevent temperatures higher then present day, otherwise the earth would never have experienced temperatures higher then present day. The uncertainty, however, cuts both ways and could mean more warming then currently predicted, and AFIK there is nothing other then wishful thinking to speak against this.

 

[spacediver]

here's a very cool animation that weighs in on the topic.

http://wakeupfreakout.org/film/tipping.html

 

[GreyICE]

Not quite. No other source of CO2 approaches what is stored in carbonate rock, and the Earth could become like Venus if it got hot enough for this stuff to break down. That said, this requires a surface temperature some 100+ degrees warmer then current, and there is no known mechanism for that to occur. Even if all the other sources of CO2 were to be released it wouldn’t create enough warming for this to happen.

No, because there's a maximum amount of heat that can be absorbed in the CO2 absorption bands, period, the end. The earth only emits a certain amount of light on those frequencies, and CO2 does NOT absorb outside those bands.

Once those bands are saturated, that is that. There's no more heat being emitted on those bands.

Venus has such a mess of an atmosphere that its damn near saturated on EVERY band. That's quite different.

The sections of IPCC which affirm the uncertainty in solar and cloud effects
must be all good old lies ...

Otherwise, you deny the IPCC...

A Denier?

Hey, MHaze, one day you shall quote me in context. I look forward to the day. At this point your approach appears to be to trim my post until it resembles whatever strawman you want to make and then just run with that strawman.

Frankly, I'm bored of that. You trimmed a three paragraph reply into one amazingly out of context sentence in the other thread, and you're not doing much better here.

Did you ever consider your audience on this site is people who have a brain? It's not your typical playschool pals on the denial blogs.

 

[mhaze]

It’s still highly unlikely that the uncertainty in cloud formation would work to prevent temperatures higher then present day, otherwise the earth would never have experienced temperatures higher then present day. The uncertainty, however, cuts both ways and could mean more warming then currently predicted, and AFIK there is nothing other then wishful thinking to speak against this.

Double talk. Zytheran offered +10C increase as the maximum temperature increase based on physical factors.

How big a metastable temperature range is there before Earth moves to the alternate stable point that exists past the (tipping points, runaway, blah blah blah). Either degrees C, K, F, or R may be used in the answer.
​

If this question cannot be answered...the "metastable climate" phrasing....then, like the question of "what is the equilibrium climate temperature"....the question is not phrased correctly and should be rephrased in accordance with the phenomena so that an answer is possible.

 

[lomiller]

No, because there's a maximum amount of heat that can be absorbed in the CO2 absorption bands, period, the end.

I’m not sure it’s truly possible to saturate absorption because temperature will climb until equilibrium is obtained. Regardless even on Venus saturation is not reached.

The earth only emits a certain amount of light on those frequencies, and CO2 does NOT absorb outside those bands.

Once those bands are saturated, that is that. There's no more heat being

CO2 absorption bands spread with higher atmospheric pressure.

Venus has such a mess of an atmosphere that its damn near saturated on EVERY band. That's quite different.

Venus’s atmosphere is 98% CO2. It’s so warm precisely because of that thick CO2 atmosphere. There is enough carbonate rock to create a similar atmosphere on earth if it were to be released. Remember Venus acutely has less slightly solar energy make it’s way into the atmosphere then the earth does because of it’s much higher albedo.

 

[mhaze]

....Hey, MHaze, one day you shall quote me in context. I look forward to the day. At this point your approach appears to be to trim my post until it resembles whatever strawman you want to make and then just run with that strawman.

Frankly, I'm bored of that. You trimmed a three paragraph reply into one amazingly out of context sentence in the other thread, and you're not doing much better here.....

Ah, good old lie about the feedbacks and create uncertainty.

The 'vagueness' about the feedbacks is in fact well defined. Since you've quoted the relevant sections of the IPCC report, I suppose that understanding simply does not flow from being given access to the information.

Gee, I don't know. IPCC says low understanding of clouds and solar, I just agree with them on that.

You translate that into "good old lies about feedbacks and creating uncertainty".

FACT: Warmers are much more extreme in their viewpoints than the IPCC documents.

 

[GreyICE]

Ah, good old lie about the feedbacks and create uncertainty.

The 'vagueness' about the feedbacks is in fact well defined. Since you've quoted the relevant sections of the IPCC report, I suppose that understanding simply does not flow from being given access to the information.

Gee, I don't know. IPCC says low understanding of clouds and solar, I just agree with them on that.

You translate that into "good old lies about feedbacks and creating uncertainty".

FACT: Warmers are much more extreme in their viewpoints than the IPCC documents.

FACT: Any time Mhaze writes the word FACT anything that follows is probably nothing of the sort.

Of course since MHaze has made the claim, he can conveniently provide proof that all "warmers" as he puts it, are more extreme than the IPCC (Of course since the IPCC is made up of "Warmers" one supposes that they must be more extreme then themselves, which will render his claim unlikely. He could, of course, recursively define warmer as anyone more extreme than the IPCC, which would prove his point in typical Mhaze fashion).

FACT: The uncertainties are well defined. It's called error bars, he needs to look them up.

 

[mhaze]

FACT: Any time Mhaze writes the word FACT anything that follows is probably nothing of the sort.

Of course since MHaze has made the claim, he can conveniently provide proof that all "warmers" as he puts it, are more extreme than the IPCC (Of course since the IPCC is made up of "Warmers" one supposes that they must be more extreme then themselves, which will render his claim unlikely. He could, of course, recursively define warmer as anyone more extreme than the IPCC, which would prove his point in typical Mhaze fashion).

FACT: The uncertainties are well defined. It's called error bars, he needs to look them up.

Well, I'll bite (although on occasion one does wonder if you take this too seriously - Warmers as a rule are way too serious, because of their urgent crusade to save the world before it goes past the tipping point or runaway or whatever the crisis is supposed to be).

How do you put error bars on the IPCC phrase "low understanding"?

 

[GMB]

There is no tipping point. This is a baseless leftist lie. The whole global warming movement is transparently fraudulent. That there are a bunch of people here who have fallen for this jive, without any evidence whatsoever, is a tip-off that the skeptical movement has lost its way.

 

[CapelDodger]

Double talk. Zytheran offered +10C increase as the maximum temperature increase based on physical factors.

How big a metastable temperature range is there before Earth moves to the alternate stable point that exists past the (tipping points, runaway, blah blah blah). Either degrees C, K, F, or R may be used in the answer.
​

"Temperature" of what, exactly?

If this question cannot be answered...the "metastable climate" phrasing....then, like the question of "what is the equilibrium climate temperature"....the question is not phrased correctly and should be rephrased in accordance with the phenomena so that an answer is possible.

Temperature is not important in itself; impacts are what matters. It's not important what local temperature leads to permafrost-melt, what matters is the melt. What we can say, from observation, is that Arctic temperatures are now sufficient to melt permafrost which has been accumulating for thousands of years. That represents a tipping-point, because it releases CO2 and CH4 in its own right.

Where will it stop? Absent a strong cooling forcing it will stop when the permafrost has released all the CO2 and CH4 that it's going to. Exactly how much that will be nobody knows; exactly what impact it will have on global temperatures is not known. What we do know is that the impact will be substantial (just from the basic science). There's one heck of a lot of organic material in the permafrost, after all. That we do know.

 

[CapelDodger]

There is no tipping point. This is a baseless leftist lie. The whole global warming movement is transparently fraudulent. That there are a bunch of people here who have fallen for this jive, without any evidence whatsoever, is a tip-off that the skeptical movement has lost its way.

There's a Conspiracy Forum at http://www.internationalskeptics.com/forums/forumdisplay.php?f=91 . You might feel more at home there.