Climate Sensitivity and timing

[dabize]

The forcing you are describing has been run in GCMs...I'm not sure why you keep disregarding this. Yet, we never saw global temp rise go insane. We saw several models accelerate the rise, but still well within the bounds of typical climate sensitivity.

I guess your contention is that as soon as we go ice-free, the models can't handle it. But considering most GC models (at least via the IPCC) are over-estimating global warming in recent years, its hard to fathom that we will all of the sudden spike 0.5C per decade when the ice is gone...unless we actually lose all the ice in June which is not happening this century.

Seems to me that the surface readings are from an admittedly incomplete set of loci that have shown more rise when Arctic sites are included. Or are they are swamped by natural variation? That last has been accounted for in peer reviewed literature, as you know.

Even if you take the surface readings as the only indicator of global surface temperature, do you not think it likely that some of this "missing" heat ends up in the deeper layers of the ocean, which (AFAIK) have been warming over the past 30 years? Or do you actually think that the laws of physics that determine Earth's overall heat budget have been revoked?

No. My contention is that the models can't handle the situation NOW, because otherwise they'd have reproduced current conditions in the Arctic.

Can you explain why we are now at 20% of what used to be normal ice volume? No? The models can't either.

There is an unaccounted variable (probably a number of them) that produced the unmodelled events of the past 6 years in the Arctic. Is it increased exchange between the surface and deeper layers or increased "convective" melting or increased ice fragmentation due to increased storms? Or a combination working with any number of other factors?

I don't know......do you? Do you think that any model in use right now accounts for that at all?

I DO know that they don't account for - the observed Arctic melt over the past few seasons.

You appear to be going out of your way to avoid the most obvious contributor to AGW.

[dabize]

This doesn't address anything in my post. The inherent danger in trying to extrapolate changes to the rest of the globe from the Arctic are apparent. There is a clear disconnect, that's not going to suddenly change.

GLOBAL warming.

Who is extrapolating?

I'd like to know how the Arctic and global conditions are related. You don't do that by dismissing the importance of the Arctic by fiat.

[ORH_wxman]

Seems to me that the surface readings are from an admittedly incomplete set of loci that have shown more rise when Arctic sites are included. Or are they are swamped by natural variation? That last has been accounted for in peer reviewed literature, as you know.

Even if you take the surface readings as the only indicator of global surface temperature, do you not think it likely that some of this "missing" heat ends up in the deeper layers of the ocean, which (AFAIK) have been warming over the past 30 years? Or do you actually think that the laws of physics that determine Earth's overall heat budget have been revoked?

No. My contention is that the models can't handle the situation NOW, because otherwise they'd have reproduced current conditions in the Arctic.

Can you explain why we are now at 20% of what used to be normal ice volume? No? The models can't either.

There is an unaccounted variable (probably a number of them) that produced the unmodelled events of the past 6 years in the Arctic. Is it increased exchange between the surface and deeper layers or increased "convective" melting or increased ice fragmentation due to increased storms? Or a combination working with any number of other factors?

I don't know......do you? Do you think that any model in use right now accounts for that at all?

I DO know that they don't account for - the observed Arctic melt over the past few seasons.

You appear to be going out of your way to avoid the most obvious contributor to AGW.

You think melting arctic sea ice is the most obvious contributor?

We'll agree to disagree on that one. You seem to be focusing on a small area of the globe. We've gained ice in the Antarctic region...its possible we have gained 1% ice mass per year there too. If that is happening then we are getting a lot of water freezing into snow and ice over the antarctic region which would be latent heat release. I'm not saying that it equals the arctic ice melt, but it definitely offsets it partially.

You only want to focus on the northern hemisphere and particularly the arctic. This is a global economy, not arctic.

[TerryM]

I think one of the reasons we are talking past each other is that some see an ice free Arctic by the solstice (an easy place to balance albedo from) as extremely unlikely to happen in the near future while others, myself included, see it as likely to be experienced soon.

Would we be in agreement that if this occurs - regardless of when - it will have a profound effect on NH temperatures?

ORH has repeatedly stated that models have shown an ice free Arctic having little effect on global temperatures - Do links to these models exist, as I'd like to see if they're taking insolation and latent heat into consideration. It doesn't seem reasonable to me that adding both of these to the global figures would not make a notable difference.

I'm not convinced that Antarctic ice extent during southern winter is more than a minor distraction. When the sun has already set, the amount of ice cover becomes irrelevant.

Sorry I keep drifting to the Arctic, but the cyclic melt and freeze of polar ice is what has kept the world within the relatively narrow range of temperatures we've experienced during the Holocene.

Terry

[ORH_wxman]

I think one of the reasons we are talking past each other is that some see an ice free Arctic by the solstice (an easy place to balance albedo from) as extremely unlikely to happen in the near future while others, myself included, see it as likely to be experienced soon.

Would we be in agreement that if this occurs - regardless of when - it will have a profound effect on NH temperatures?

ORH has repeatedly stated that models have shown an ice free Arctic having little effect on global temperatures - Do links to these models exist, as I'd like to see if they're taking insolation and latent heat into consideration. It doesn't seem reasonable to me that adding both of these to the global figures would not make a notable difference.

I'm not convinced that Antarctic ice extent during southern winter is more than a minor distraction. When the sun has already set, the amount of ice cover becomes irrelevant.

Sorry I keep drifting to the Arctic, but the cyclic melt and freeze of polar ice is what has kept the world within the relatively narrow range of temperatures we've experienced during the Holocene.

Terry

If the arctic is ice free in the summer after mid August every year...it would produce roughly a +0.02C per decade rise in the global warming scheme (being generous in the 10% added warming). This is hardly evidence for some monster rise to get us to 0.5C per decade. Unless you have some papers that show us the math is wrong or that we are missing something, I'm not sure what you arguing. Maybe that all of the sudden we will have completely ice free arctic by June? Considering we can't even do it yet by September, I hardly find this reasonable in the near future.

[tacoman25]

Who is extrapolating?

I'd like to know how the Arctic and global conditions are related. You don't do that by dismissing the importance of the Arctic by fiat.

I'm not dismissing the importance of the Arctic. I'm pointing out that it's important not to read too much into how much change has occurred in the Arctic because 1) the Arctic is more prone to extreme changes by nature and 2) the global temperature trend has not followed Arctic conditions thus far. There is no reason to believe this will suddenly change anytime soon.

[skierinvermont]

I think one of the reasons we are talking past each other is that some see an ice free Arctic by the solstice (an easy place to balance albedo from) as extremely unlikely to happen in the near future while others, myself included, see it as likely to be experienced soon.

Would we be in agreement that if this occurs - regardless of when - it will have a profound effect on NH temperatures?

ORH has repeatedly stated that models have shown an ice free Arctic having little effect on global temperatures - Do links to these models exist, as I'd like to see if they're taking insolation and latent heat into consideration. It doesn't seem reasonable to me that adding both of these to the global figures would not make a notable difference.

I'm not convinced that Antarctic ice extent during southern winter is more than a minor distraction. When the sun has already set, the amount of ice cover becomes irrelevant.

Sorry I keep drifting to the Arctic, but the cyclic melt and freeze of polar ice is what has kept the world within the relatively narrow range of temperatures we've experienced during the Holocene.

Terry

As I said before .. the global forcing from albedo even if we are ice free from mid June to darkness is still only 15% or so of the forcing from CO2 and water vapor combined.

We're talking about 5 million sq km of lost ice on a planet of 510 million sq km.

Someone should probably double check my calculations especially my assumption that such a concentrated regional forcing would have only have half (edit missing word) the global forcing as if it were evenly dispersed. Even if you ignore that assumption you're talking about only 30%.

[ORH_wxman]

As I said before .. the global forcing from albedo even if we are ice free from mid June to darkness is still only 15% or so of the forcing from CO2 and water vapor combined.

We're talking about 5 million sq km of lost ice on a planet of 510 million sq km.

Someone should probably double check my calculations especially my assumption that such a concentrated regional forcing would have only have the global forcing as if it were evenly dispersed. Even if you ignore that assumption you're talking about only 30%.

Is there a reason to assume otherwise? Global heat gets dispersed fairly quickly if we go on the past. At least if we are talking on the scale of a century....but usually on the scale of a few years.

[TerryM]

If the arctic is ice free in the summer after mid August every year...it would produce roughly a +0.02C per decade rise in the global warming scheme (being generous in the 10% added warming). This is hardly evidence for some monster rise to get us to 0.5C per decade. Unless you have some papers that show us the math is wrong or that we are missing something, I'm not sure what you arguing. Maybe that all of the sudden we will have completely ice free arctic by June? Considering we can't even do it yet by September, I hardly find this reasonable in the near future.

I won't argue with your figure - at least for the moment, but if that 0.02C/decade is concentrated in the Arctic, don't you think it will add significantly to next years ice? It was you I believe who pointed out what a tiny percentage of the globe the Arctic encompases.

I don't think that a week or two in August will have much global impact, but I do think it will have quite a large local impact.

Terry

BTW, I really would like the link to the models you referenced - this isn't a "gotcha", I want to see what they were doing with both latent heat and with insolation.

[TerryM]

As I said before .. the global forcing from albedo even if we are ice free from mid June to darkness is still only 15% or so of the forcing from CO2 and water vapor combined.

We're talking about 5 million sq km of lost ice on a planet of 510 million sq km.

Someone should probably double check my calculations especially my assumption that such a concentrated regional forcing would have only have the global forcing as if it were evenly dispersed. Even if you ignore that assumption you're talking about only 30%.

It's going to be a few days before I can run the math, I'm on another two blogs at the moment, and the wife has lots of plans for tomorrow.

I'd be inclined to think that a 15% pulse of additional energy adding cumualtively each northern summer migh get to be important quite rapidly. Did you also run the figures for 850 cubic km of ice not being melted each year - the latent heat figure should be in the neighborhood of 2.5 10²⁰J I believe, and again its cumulative each summer.

Terry

[ORH_wxman]

I won't argue with your figure - at least for the moment, but if that 0.02C/decade is concentrated in the Arctic, don't you think it will add significantly to next years ice? It was you I believe who pointed out what a tiny percentage of the globe the Arctic encompases.

I don't think that a week or two in August will have much global impact, but I do think it will have quite a large local impact.

Terry

BTW, I really would like the link to the models you referenced - this isn't a "gotcha", I want to see what they were doing with both latent heat and with insolation.

This is already assuming an ice free arctic from August onward until refreeze. This is not current.

As for the models, I don't have them at my fingertips as they are papers I read throughout the last couple years, but I will try and link them to you when I find them. GCMs in general are run with a lot of parameters set to various levels and arctic sea ice is one of them.

[ORH_wxman]

So outside of this predictable arctic debate...does anyone want to discuss the global sensitivity and the timing?

[skierinvermont]

It's going to be a few days before I can run the math, I'm on another two blogs at the moment, and the wife has lots of plans for tomorrow.

I'd be inclined to think that a 15% pulse of additional energy adding cumualtively each northern summer migh get to be important quite rapidly. Did you also run the figures for 850 cubic km of ice not being melted each year - the latent heat figure should be in the neighborhood of 2.5 10²⁰J I believe, and again its cumulative each summer.

Terry

The effects of radiative forcing are not cumulative. Once global surface temperature rise, the global energy budget becomes balanced.

No need to do the math yourself. I have finally found a paper that directly addresses the question. My estimates were alarmingly accurate if I do say so myself.

http://www.npolar.no...edoFeedback.pdf

An annually ice free state results in .7W/m2 of radiative forcing. A seasonally ice free state results in .3W/m2 of forcing. By comparison forcing from doubling CO2 alone is 3.7W/m2 and results in just over 1C of warming, not including all the feedbacks.

Thus additional global warming caused by seasonally ice free state is less than .1C.

An annual ice free state results in .2C of additional global warming. As I argued before, arctic sea ice is not especially important to the climate sensitivity, the topic of this thread.

I rest my case.

http://www.npolar.no...edoFeedback.pdf

It's a relevant factor to mention in this thread, but hopefully we can move on to the big fish now.

EDIT: One more thing to add now that I've finished the paper. They note that their calculations assume no change in cloud cover. If cloud cover increases 15% in summer, then the forcing for an ice-free summer is actually negative (-.31W/m2). While the increase in clouds probably won't be 15%, the actual RF for an ice free summer is probably less than the previously stated .3W/m2.

[dabize]

The effects of radiative forcing are not cumulative. Once global surface temperature rise, the global energy budget becomes balanced.

No need to do the math yourself. I have finally found a paper that directly addresses the question. My estimates were alarmingly accurate if I do say so myself.

http://www.npolar.no...edoFeedback.pdf

An annually ice free state results in .7W/m2 of radiative forcing. A seasonally ice free state results in .3W/m2 of forcing. By comparison forcing from doubling CO2 alone is 3.7W/m2 and results in just over 1C of warming, not including all the feedbacks.

Thus additional global warming caused by seasonally ice free state is less than .1C.

An annual ice free state results in .2C of additional global warming. As I argued before, arctic sea ice is not especially important to the climate sensitivity, the topic of this thread.

I rest my case.

http://www.npolar.no...edoFeedback.pdf

It's a relevant factor to mention in this thread, but hopefully we can move on to the big fish now.

Interesting paper, and clearly presented.

I did note that the ice free scenarios contemplated in the paper would increase the current AGW rates worldwide by anywhere between 25% and 50% (depending on the degree of "ice freedom" - see the Discussion). That seems pretty significant to me, especially if the effect is cumulative.

Hardly a "small fish"........BTW - what ARE these big fish?

[skierinvermont]

Interesting paper, and clearly presented.

I did note that the ice free scenarios contemplated in the paper would increase the current AGW rates worldwide by anywhere between 25% and 50% (depending on the degree of "ice freedom" - see the Discussion). That seems pretty significant to me, especially if the effect is cumulative.

Hardly a "small fish"........BTW - what ARE these big fish?

Where are you seeing that? I read the whole thing and I didn't see that anywhere and it does not make sense based on the RF values.

As I said already, the .3W/m2 would correspond to roughly .1C of additional warming (that might be enough to increase the rate of warming by 50% if it was concentrated within a single decade, but the increased rate would only last for that decade.. the .1C is cumulative not a change in rate)

The .7W/m2 would correspond to roughly .2C of additional warming.

The big fish are water vapor and cloud cover. You can also estimate climate sensitivity with paleoclimate studies.

[skierinvermont]

SkepticalScience has a good summary of current climate sensitivity estimates, with a good number of links to the literatures:

http://www.skepticalscience.com/climate-sensitivity-advanced.htm

I found this graphic particularly illustrative of the current state of knowledge and the various lines of evidence:

[skierinvermont]

One of the papers to linked to by Hansen is interesting for its differentiation of fast and slow climate sensitivity. He argues the fast sensitivity is 3C and the slow is 6C because of ice sheet collapse and oceanic CO2 release. The evidence is the fact that the interglacials were caused by relatively small initial forcings and yet led to 6C+ swings in temperature.

[TerryM]

Skier

Your paper addresses radiative changes only

From PIOMAS"

"It takes energy to melt sea ice. How much energy? The energy required to melt the 16,400 Km³ of ice that are lost every year (1979-2010 average) from April to September as part of the natural annual cycle is about 5 x 10²¹ Joules. For comparison, the U.S. Energy consumption for 2009 (www.eia.gov/totalenergy) was about 1 x 10²⁰ J. So it takes about the 50 times the annual U.S. energy consumption to melt this much ice every year. This energy comes from the change in the distribution of solar radiation as the earth rotates around the sun."

Since this energy is presently used to melt the ice each summer, it is energy that would be released each year in an ice free environment - and is therefore cumulative. Some of course would be radiated away during winter - unless there is sufficient cloud cover to prevent this - but unless 100% is radiated away, the accumulation continues.

I read a paper recently that assumed the only way palm trees and alligators could have survived in the high Arctic was if heavy cloud cover had been preventing the outgoing radiation during the period when the sun wasn't shining.

Latent heat calculations aren't esoteric, it's pretty basic physics. If you know the amount of ice being melted, you know the amount of energy used. If the ice is removed or melted the energy becomes sensible heat.

Terry

[ORH_wxman]

One of the papers to linked to by Hansen is interesting for its differentiation of fast and slow climate sensitivity. He argues the fast sensitivity is 3C and the slow is 6C because of ice sheet collapse and oceanic CO2 release. The evidence is the fact that the interglacials were caused by relatively small initial forcings and yet led to 6C+ swings in temperature.

That was actually pretty interesting. I think the claim for a slower (but much higher sensitivity) response was valid. I think the fast response is not behaving like they think though....but obviously we have more time to assess that.

[ORH_wxman]

Skier

Your paper addresses radiative changes only

From PIOMAS"

"It takes energy to melt sea ice. How much energy? The energy required to melt the 16,400 Km³ of ice that are lost every year (1979-2010 average) from April to September as part of the natural annual cycle is about 5 x 10²¹ Joules. For comparison, the U.S. Energy consumption for 2009 (www.eia.gov/totalenergy) was about 1 x 10²⁰ J. So it takes about the 50 times the annual U.S. energy consumption to melt this much ice every year. This energy comes from the change in the distribution of solar radiation as the earth rotates around the sun."

Since this energy is presently used to melt the ice each summer, it is energy that would be released each year in an ice free environment - and is therefore cumulative. Some of course would be radiated away during winter - unless there is sufficient cloud cover to prevent this - but unless 100% is radiated away, the accumulation continues.

I read a paper recently that assumed the only way palm trees and alligators could have survived in the high Arctic was if heavy cloud cover had been preventing the outgoing radiation during the period when the sun wasn't shining.

Latent heat calculations aren't esoteric, it's pretty basic physics. If you know the amount of ice being melted, you know the amount of energy used. If the ice is removed or melted the energy becomes sensible heat.

Terry

Right, and that has been calculated. I'm not quite sure why this keeps getting overlooked.

[skierinvermont]

Skier

Your paper addresses radiative changes only

From PIOMAS"

"It takes energy to melt sea ice. How much energy? The energy required to melt the 16,400 Km³ of ice that are lost every year (1979-2010 average) from April to September as part of the natural annual cycle is about 5 x 10²¹ Joules. For comparison, the U.S. Energy consumption for 2009 (www.eia.gov/totalenergy) was about 1 x 10²⁰ J. So it takes about the 50 times the annual U.S. energy consumption to melt this much ice every year. This energy comes from the change in the distribution of solar radiation as the earth rotates around the sun."

Since this energy is presently used to melt the ice each summer, it is energy that would be released each year in an ice free environment - and is therefore cumulative. Some of course would be radiated away during winter - unless there is sufficient cloud cover to prevent this - but unless 100% is radiated away, the accumulation continues.

I read a paper recently that assumed the only way palm trees and alligators could have survived in the high Arctic was if heavy cloud cover had been preventing the outgoing radiation during the period when the sun wasn't shining.

Latent heat calculations aren't esoteric, it's pretty basic physics. If you know the amount of ice being melted, you know the amount of energy used. If the ice is removed or melted the energy becomes sensible heat.

Terry

You have terribly confused the issue.

I agree there are two separate issues affecting surface temperature. 1) The change in albedo that alters the global energy budget. I addressed this point already (<.3W/m2 seasonal ice free= .1C cumulative warming, <.7W/m2 annual ice free=.2C cumulative warming)

2) The issue you bring up. The energy from summer solar insolation instead of going into melting the ice goes into increasing temperature. Instead of melting 16,400 cubic km of ice each summer, we will only melt 15,000, or 12,000 maybe. So you have to melt 1,400, or 3,400 etc. cubic km less. You haven't altered the amount of energy. You have only altered whether the summer insolation goes into melting or temperature increase.

However, in the fall you are likewise generating an equal quantity less ice. Which means that an equal quantity of energy released results in lower temperatures rather than phase transition.

Because near equal amounts of ice are melted and re-frozen each fall it cannot have an effect on temperature. In so far as you have to use less energy to phase transition from ice to water for 3,000 cubic km less ice each summer, you also have to use less an equal amount less energy in phase transition from water to ice each fall. You are melting and refreezing near equal amounts of ice each summer and fall. There is no net effect on temperature. 1 billion fewer Joules are used for melting ice (converting potential energy to kinetic energy), 1 billion fewer Joules are used for freezing ice (converting kinetic to potential energy)

[CoastalWx]

As a met who understands the physics behind what we have been talking about, but not up to date with the latest literature, this is a good thread. Nice link above Skier.

[Snow_Miser]

Here is what the IPCC has to say about the Climate Sensitivity.

Using feedback parameters from Figure 8.14, it can be estimated that in the presence of water vapor, lapse rate and surface albedo feedbacks, but in the absence of cloud feedbacks, current GCMs would predict a climate sensitivity (±1 standard deviation) of roughly 1.9°C ± 0.15°C (ignoring spread from radiative forcing differences). The mean and standard deviation of climate sensitivity estimates derived from current GCMs are larger (3.2°C ± 0.7°C) essentially because the GCMs all predict a positive cloud feedback (Figure 8.14) but strongly disagree on its magnitude.”

This means that the models have a very strong positive cloud feedback taking shape, as the Cloud Feedback constitutes about 1.3 Degrees C of the 2.0 Degree C amplification from the positive feedbacks in the models. This represents 65% of the positive feedback that the IPCC models predict as coming from the positive cloud feedback.

This means that if the models are getting the Cloud Feedback completely wrong, then climate sensitivity is MUCH lower than 3.2 Degrees C and much lower than 1.9 Degrees C.

There is evidence that models are very poor at modeling cloud microphysics properties.

See for example

http://www.mi.uni-ha...er_AtmosRes.pdf

And there is some observational evidence for a negative cloud feedback taking place in observations.

For example see these papers:

http://blog.acton.or...encer_07GRL.pdf

The paper above finds a sensitivity of 6.1 w/m^2/K, which represents strong negative feedback.

http://www.iup.uni-h...007JD008746.pdf

The author above assumes that all of the warming is due to anthropogenic sources, and even this gives you a sensitivity of 3.3 w/m^2/K, or 1.1 Degrees C per doubling of CO2. However, the assumption that all of the warming over the 20th Century can be ascrbied to anthropogenic sources is wrong, see for example:

http://www.springerl...287231175q2643/

http://scienceandpub...man_induced.pdf

http://geology.geosc.../5/471.abstract

http://www.sciencedi...364682611002896

http://www.springerl...8u12g2617j5021/

http://www.springerl...11048377749k84/

http://www.ldeo.colu...nauskasetal.pdf

http://www.springerl...0rn84j83268356/

http://www.friendsof.../Rao-GCR_GW.pdf

When accounting for natural contributions of warming from the Rao 2011 paper, it is possible to estimate the sensitivity to be around 5.5 w/m^2 which represents substantial negative feedback.

These two papers also document the negative feedback from cloud changes to warming

http://www.agu.org/p...2GL052700.shtml

http://www.agu.org/p...1GL050506.shtml

So if the Cloud Feedback is negative, then there is the possibility that the sensitivity to a doubling of CO2 may be at a blackbody sensitivity or even lower.

[ORH_wxman]

Most people agree on the sensitivity range. The more interesting question is how that change will be manifested yearly

as it overlaps with natural variability. The Texas State climatologist shows why it's important to take ENSO into

account. Some people have been mistaking a series of Nina years as a slowdown or a stop in global warming.

When papers like I posted earlier break it down, it shows how steady the warming has been. I was asking questions

about how long and the rate of the warming, not disputing the general sensitivity ranges that Rusty and others

have discussed. I am more interested in zonal temperature changes rather than an averaged out global value.

So I was focused more on the timing portion of your original post not the actual sensitivity.

http://blog.chron.co...ack-of-warming/

Well yes, of course the natural variation "covers" up the anthropogenic forcing when we go into negative ENSO decadal phases (i.e. a negative PDO). That has kind of been the point in a lot of these discussions about the 1980s and 1990s warming. It was influenced by the positive PDO phase. There are varying degrees of the PDO influence in the literature on global temps. One paper Don posted said that a negligible amount of warming from 1975-2005 was from the PDO...another paper I posted said one third of the warming was aided by the positive PDO.

There are obviously still some differences to be resolved. But how does this fit into this thread? I think its important to isolate the anthropogenic trend if we are to get a good sense of the timing of the sensitivity.

[noiv]

> I think arguably the most important aspect of climate change is figuring out the sensitivity and how long it takes to reach that target. Sea level rise is probably the most important consequence, but this is more or less a direct cause of sea level rise, so roughly the same difference when talking about the two over a longer term scale.

Sea level rise is slow, adaption a matter of decades. Consequences of a warming Arctic will arrive probably too fast for the northern hemisphere, they are a matter of months and years. Not sure from what point of view you define 'important', it'd would help to keep this discussion focused if you elaborate a bit on that.

> ... the year-long ice has not seen quite the same decrease since winter ice hasn't declined nearly as fast.

Actually, it is the other way around, volume loss during the Summer is only slightly increasing. The real problem is not enough ice is build during Winter.

> I knew this thread would probably turn into an arctic ice obsession. But that is such a small part of the globe. We can also at least subtract like a half a million sq km off the albedo effect in the arctic since we are trending higher in the antarctic. But overall, these are relatively minor points in the sensitivity of the planet.

A 1% change in Earth’s planetary albedo exerts a forcing almost as large as a doubling of CO2. Dropping snow anomalies and bringing up Antarctica's Winter albedo doesn't look exactly fair - to say the best. If you really want to know and discuss global forcing by CO2, there is no way to exclude cryospheric forcing. At least if your starter post has any meaning.

[dabize]

A 1% change in Earth’s planetary albedo exerts a forcing almost as large as a doubling of CO2. Dropping snow anomalies and bringing up Antarctica's Winter albedo doesn't look exactly fair - to say the best. If you really want to know and discuss global forcing by CO2, there is no way to exclude cryospheric forcing. At least if your starter post has any meaning.

Bingo

It is hard to see how the Arctic isn't going to be the leading source of forcing - the interesting part is how Arctic changes will be propagated around the world.

To ignore this with the determination we've seen here makes one think of lines such as this:

"Where ignorance is bliss, 'tis folly to be wise."

[skierinvermont]

Bingo

It is hard to see how the Arctic isn't going to be the leading source of forcing - the interesting part is how Arctic changes will be propagated around the world.

To ignore this with the determination we've seen here makes one think of lines such as this:

"Where ignorance is bliss, 'tis folly to be wise."

Leading source of forcing? Is this a joke? I have already provided ample evidence that it is not even close.

Seasonal ice free conditions provides .3W/m2 of forcing. A 4 million sq km snow cover anomaly provides something like .5W/m2 for a whopping total of .8W/m2.

Compare that to 3.7W/m2 for doubling CO2, and what is likely to be a ~3W/m2 water vapor feedback for a 6.7W/m2 total effect.

6.7W/m2 vs .8W/m2... you tell me which is bigger?

[tacoman25]

What happens in the Arctic has an effect on circulation and temperature patterns across the Northern

Hemisphere where most of the people on the planet currently live. Asking a question about the future

progression of these changes is not a conclusion.

Focusing mainly on the Arctic in a thread about overall global response to CO2 doesn't make a lot of sense though, especially when we haven't seen global trends follow the Arctic to this point. There is no evidence of changes in the Arctic causing increased global warming to this point.

[skierinvermont]

One more chart illustrating my point. Water vapor has a feedback of 1.9W/m2/C, by comparison the surface albedo feedback is .2-3W/m2/C (incidentally for 3C of warming that is .8W/m2, which is exactly what I estimated above),

[The_Global_Warmer]

If you guys don't want to talk arctic, then don't talk bout other factors.