Climate Sensitivity and timing

[ORH_wxman]

I have had a few exchanges with WeatherRusty over the past few months in various threads talking about climate sensitivity and how long it takes to reach that number per doubling of CO2.

I thought I would start a thread here and people can post papers or ideas on this aspect. 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.

There are obviously different figures in peer review of climate sensitivity ranging from under 1C to over 6C...of course most of those end points are not believed to be likely and the estimates generally fall in between 1.7C and 3.5C...perhaps up to 4.5C as the IPCC uses as an upper bound. Another very important aspect of this is how long does it take to reach that level of warming. There is a huge difference between warming 2.5C in 100 years and taking 250 years to do it.

Here are a few papers on the sensitivity.

http://www.iac.ethz.ch/doc/publications/Chylek-Lohmann-GRL2008.pdf

http://epic.awi.de/24112/1/Khl2011c.pdf (in presentation format but based on Kohler et al 2010)

http://mgg.coas.oregonstate.edu/~andreas/pdf/S/schmittner11sci_man.pdf

IPCC 2007 take: http://www.ipcc.ch/publications_and_data/ar4/syr/en/mains2-3.html (a bit annoying to jump around with the links they have)

There are a lot more, but these are just a few that generally fall in the accepted values. What I can't really find are very good papers on 21st century warming.

I have found this paper: http://www.agu.org/pubs/crossref/2012/2011GL050226.shtml which says that 21st century warming will be in the 1.3-1.8C range.

I also found an interesting older paper by James Hansen et al in 2000 that talks about it from a slightly different perspective: http://www.giss.nasa.gov/research/features/200111_altscenario/

At any rate, I thought this would be a good thread for stuff like this. I have often looked for papers that talk about the timing of the warming, and there are surpsingly many fewer of these papers than there are on general climate sensitivity. IPCC has a slew of their models on warming through the 21st century...most of which are very agressive.

http://www.ipcc-data.org/data/ar4_multimodel_globalmean_tas.txt

[TerryM]

On this thread will we be concentrating solely on the effects of doubled C02 as opposed to feedbacks such as CH4 releases that will ensue, or will all the ramifications - loss of Arctic sea ice and the albedo changes, the latent heat issues caused by lessening of ice to melt and the rising atmospheric moisture content all be included in the discussion.

Sea level rise has, until very recently been driven by thermal expansion. Now with GIS melt contributing more than expansion, and the prospect of PIG collapse in the Antarctic within an unknown time frame a concern, the thermal component may be of lessening import.

Would you want these factors discussed on this thread also?

Terry

[ORH_wxman]

On this thread will we be concentrating solely on the effects of doubled C02 as opposed to feedbacks such as CH4 releases that will ensue, or will all the ramifications - loss of Arctic sea ice and the albedo changes, the latent heat issues caused by lessening of ice to melt and the rising atmospheric moisture content all be included in the discussion.

Sea level rise has, until very recently been driven by thermal expansion. Now with GIS melt contributing more than expansion, and the prospect of PIG collapse in the Antarctic within an unknown time frame a concern, the thermal component may be of lessening import.

Would you want these factors discussed on this thread also?

Terry

All factors should be included...the feedbacks are what make the sensitivity uncertain itself. We already know the CO2 sensitivity in a vacuum, its about 1C per doubling if I am not mistaken. The arguments for less sensitivity is that cloud feedbacks reflect more incoming shortwave radiation to offset the blocking of outgoing longwave radiation. Ice albedo feedbacks are accounted for in most simulations because its easy to remove or add ice to adjust for different outcomes when making error bars. Clouds are more difficult because its not just clouds themselves that are hard to adjust (since they cover a lot more area than ice), but the type of clouds too. Certain high clouds have more albedo than lower level clouds.

[ORH_wxman]

I would be interested in seeing some studies done on Northern Hemisphere temperature projections

for the rest of this century based on the much more rapid melting of the Arctic sea ice that has

occurred. The current Arctic sea ice levels are closer to were we were supposed to be later in

this century. You can also see the Arctic amplification really take hold for the Northern Hemisphere

since the turn of the century.

We are only at the minimum ice extent projected for later in the century....the year-long ice has not seen quite the same decrease since winter ice hasn't declined nearly as fast.

Regardless, rather than splitting this into another arctic sea ic thread, I agree with your interest in seeing some purely northern hemisphere projections. GISS has the northern hemisphere at about +0.07C per decade since 2001 and the Southern Hemisphere at about -0.07C per decade in the same time frame. That is actually a considerably slower rise than we saw in the 1980s and 1990s. The seperation between the two however has become much larger since then.

[TerryM]

I'd assume that nocturnal clouds would also act much as winter clouds in the Arctic and effectively blanket the surface preventing outgoing radiation.

I'm not sure of this, but I'd assume that the way things play out in the Arctic is going to have a huge effect on whatever number is arrived at. Since virtually none of the models have captured the changes there in anything close to the timeframe we're seeing it may be reasonable to assume that the models are at present are using far too low a figure.

I realise that the Arctic is but a small percentage of the world's surface, but because of the ice and the large amount of energy involved in phase change it exerts far more influence than it's size would warrant. The doubling of C02 that we are now in the middle of is the one that will see the end to Arctic ice, and this doubling will be far more important than any succeeding ones for this reason. If we could somehow end any energy inputs at the moment when this doubling from preindustrial levels takes place, the Antarctic cap would eventually melt - slowly perhaps, but eventually it would go.

For this reason I'm not sure that the effects of doubling C02 holds great meaning. Once the ice is gone, the effects will be less, once all the methane has been released, the effects will be less, should the ocean reach boiling temperatures at some time in the far future, the effects will approach zero.

If we're in agreement that the present doubling is sufficient to at least produce a seasonally ice free Arctic, and that the ramifications of this will fundamentally alter future calculations, might it not be wiser to limit ourselves to this particular doubling as opposed to trying to figure out what will happen when we're facing an Eemian climate?

Terry

[ORH_wxman]

When you take into account solar and ENSO, the global warming signal remains unchanged.

But the Arctic has warmed rapidly especially during the fall and winter over last decade.

We have also seen a steep decline in spring NH snow cover which has contributed to record

warmth.

We can both probably agree that it would be helpful to run some NH temperature projections

based on these updated initial conditions.

http://iopscience.io...44022/fulltext/

That paper claims to get rid of the ENSO signal, but its still very apparent on there. I'm not saying their whole paper is flawed...I agree that of course once we eliminate natural variation, there is an underlying GW signal. However, that paper's graph does not get rid of natural variation if we are still seeing ENSO signals.

[TerryM]

Bluewave

The very recent paper you linked says that the median figure at the moment is 3C per doubling, (without factoring in permafrost).

Do you have any idea whether anyone is addressing the collapse of the Arctic sea ice in their figures. It seems possible that estimates made prior to this August would underplay this possibility.

Terry

[dabize]

You mean: winter ice EXTENT hasn't declined so fast.

This distinction is important, since the (unmodeled) albedo changes and attendant increase in summer energy absorption are ultimately dependent on the (unmodeled) volume loss, which is much more significant recently, even in late winter. Extent without thickness is gone by the time that the high insolation period begins.

So I say that the models don't account for the albedo loss and its downstream consequences, since they have failed to predict what has already occured.

The point about focusing exclusively on the Arctic is well taken, but since the Arctic currently where rapid, unmodeled destabilization is occurring, it is natural to focus on it. I guess I'm agreeing with bluewave here.

I would be very interested in a serious discussion of the actual science based on what is known about how "Arctic amplification" could translate into global changes, including temperature sensitivity to atmospheric CO2, the effects on Antarctic sea ice, the WAIS etc.

BTW, an honest willingness to consider how these factors fit together would cut down on the b%tch#ng from people like me when the Antarctic, the AMO, the PDO etc are discussed, because then it wouldn't seem like a politically driven attempt to minimize or draw attention away from the consequences of AGW.

[ORH_wxman]

You mean: winter ice EXTENT hasn't declined so fast.

This distinction is important, since the (unmodeled) albedo changes and attendant increase in summer energy absorption are ultimately dependent on the (unmodeled) volume loss, which is much more significant recently, even in late winter. Extent without thickness is gone by the time that the high insolation period begins.

So I say that the models don't account for the albedo loss and its downstream consequences, since they have failed to predict what has already occured.

The point about focusing exclusively on the Arctic is well taken, but since the Arctic currently where rapid, unmodeled destabilization is occurring, it is natural to focus on it. I guess I'm agreeing with bluewave here.

I would be very interested in a serious discussion of the actual science based on what is known about how "Arctic amplification" could translate into global changes, including temperature sensitivity to atmospheric CO2, the effects on Antarctic sea ice, the WAIS etc.

BTW, an honest willingness to consider how these factors fit together would cut down on the b%tch#ng from people like me when the Antarctic, the AMO, the PDO etc are discussed, because then it wouldn't seem like a politically driven attempt to minimize or draw attention away from the consequences of AGW.

We have models that account for zero summer sea ice....and their sensitivty isn't as large as some would think. There's a reason there bracket is what it is. It's not because the climate scientists never thought of sea ice melting.

I would also say you are wrong on the ice being gone when the high insolation begins. The highest insolation is June and we have a bottleneck of ice extent in the record there. The huge discrepency in sea ice loss is later in the summer. Not in May and June which are well after "the high insolation period" begins. This is not claiming that ice is not important, its just that we are not anywhere near the ice being a lot less when that period begins like we are late in the summer when the sun is setting in the arctic.

What we know from the small record of large ice loss in the arctic is that the arctic is warming very fast....yet global temperatures havent warmed in over 10 years. This doesn't imply that arctic temps are not important, they obviously are, but they are still relatively small in the scheme of the globe.

[TerryM]

Correct me if I'm wrong, but it seems axiomatic that insolation will be split evenly at the solstice, and I wouldn't suppose that an ice free end of summer is too far into the future. If we assumed that we'll have 50 % of full insolation from solstice on, and if we assume an even melt prior to that and additional 25% prior to solstice, we're getting significant figures with seasonal ice melt.

At the moment we're melting between 800 and 900 cubic km of ice each year. That's a whole bunch more energy than the US produces on a yearly basis just in the latent heat to sensible heat equations (roughly 3 years worth). I have no idea how the hemisphere will react to cumulative heat pulses of this magnitude, but would assume that it's not a stable condition, and that winter freeze up would decline in short order.

The effect this additional heat will have on the GIS is also an unknown. This year's melt there was far above expectations and the albedo changes we've seen there don't leave much hope for a recovery - damn those microbes. While this particular doubling of C02 will undoubtedly lead to a much quicker redoubling, I'm not sure how many will be around to record it.

Perhaps it's because I haven't concentrated on any of the other areas being affected, but the Arctic seems to hold the key to where this particular doubling will go, but the Antarctic can't be too far behind.

Terry

[dabize]

I would also say you are wrong on the ice being gone when the high insolation begins. The highest insolation is June and we have a bottleneck of ice extent in the record there. The huge discrepency in sea ice loss is later in the summer. Not in May and June which are well after "the high insolation period" begins. This is not claiming that ice is not important, its just that we are not anywhere near the ice being a lot less when that period begins like we are late in the summer when the sun is setting in the arctic.

You miss the point.

I know that there are models which look at the consequences of complete melt out, and the fact that they predict recovery is certainly relevant to the discussion. However, since the models have failed to adequately account for what has happened so far, they cannot be expected to model the downstream consequences of ACTUAL melt out conditions.

As for the "high insolation period", you cannot tell me that there wasn't unparalleled melting during this past year by the end of July (or even the end of June), even though the melt season started from a relatively "normal" end of winter extent. I think a very good case can be made that we are rapidly approaching a point when an additional (large) amount of energy will be absorbed by an Arctic that is already showing rapid, unparalleled and unmodeled loss of SIA.

BTW - you say there's been no effect on global temperatures yet. Of course there hasn't - so far the effect has been spent in melting ice locally in the Arctic, where the effect on temps is limited to what is left over from latent heat of melting.

Also, I'm not saying we're there yet. I AM saying that the facts on the ground suggest we WILL be there quite soon - sometime in the next 10 years is a good bet.

It is just these things and their connections to global AGW and its various consequences/ramifications that ought to be discussed.

[dabize]

Peter Wadhams is trying to quantify these rapid changes in a recent BBC interview.

http://www.bbc.co.uk...onment-19496674

Exactly- he touches on all the key points.

BTW - I rather wish he hadn't associated himself with AMEG, since there's really no need to drag CH4 into it; it is much more iffy than the other factors, which are plenty frightening enough when considered together.

[skierinvermont]

I think most posters vastly overestimate the significance of arctic albedo loss on a global scale. From what I've read, surface albedo changes don't make that big a difference to climate sensitivity.

The primary feedbacks to CO2 are water vapor and cloud cover.

[dabize]

I think most posters vastly overestimate the significance of arctic albedo loss on a global scale. From what I've read, surface albedo changes don't make that big a difference to climate sensitivity.

The primary feedbacks to CO2 are water vapor and cloud cover.

How can you say this? The changes in water vapor and cloud cover, perhaps, but these are changing all the time everywhere, and assigning a specific AGW component to them is currently impossible.

The albedo effect is/will be huge and well understood. It is equivalent to the amount of energy taken in by a similar sized area near the equator (say the Sahara- maybe) over the same time.

Admittedly, a significant proportion (by no means all) of this energy will be re-radiated during the winter, but the magnitude of this is one of the things that will need discussion.

[ORH_wxman]

You miss the point.

I know that there are models which look at the consequences of complete melt out, and the fact that they predict recovery is certainly relevant to the discussion. However, since the models have failed to adequately account for what has happened so far, they cannot be expected to model the downstream consequences of ACTUAL melt out conditions.

As for the "high insolation period", you cannot tell me that there wasn't unparalleled melting during this past year by the end of July (or even the end of June), even though the melt season started from a relatively "normal" end of winter extent. I think a very good case can be made that we are rapidly approaching a point when an additional (large) amount of energy will be absorbed by an Arctic that is already showing rapid, unparalleled and unmodeled loss of SIA.

BTW - you say there's been no effect on global temperatures yet. Of course there hasn't - so far the effect has been spent in melting ice locally in the Arctic, where the effect on temps is limited to what is left over from latent heat of melting.

Also, I'm not saying we're there yet. I AM saying that the facts on the ground suggest we WILL be there quite soon - sometime in the next 10 years is a good bet.

It is just these things and their connections to global AGW and its various consequences/ramifications that ought to be discussed.

I do not doubt for one second your points. I think they are valid.

I just question how much magnitude they actually have. The models HAVE in fact simulated an ice free arctic and show the temp change really doesn;t go haywire. Mostly because the arctic really isn't that big of a space compared to the rest of the globe. There is a lot of talk about all this sunlight hitting an extra 2 million sq km of open ocean rather than ice....yet 98% of the ocean sees sunlight all the time and at a much higher sun angle than the arctic will ever see in our immediate future (perhaps one day the earth will tilt so much that the arctic has a higher sun angle...but irrelevant for this discussion)

This is about the globe, not just the arctic. I would be glad to entertain possibilities of a catastrophic rise in global temperatures if the arctic had seasonally ice-free conditions starting next year. However, this has not been shown to be the case in GCMs....and lets not forget that GCMs have already been over-predicting global temps as it is despite not predicting the ice melt fast enough.

[skierinvermont]

How can you say this? The changes in water vapor and cloud cover, perhaps, but these are changing all the time everywhere, and assigning a specific AGW component to them is currently impossible.

Well that would be unfortunate considering it is necessary to assign an AGW component to ascertain climate sensitivity. Fortunately it is possible to estimate reasonably accurate values. From 1988-2005 tropospheric water increased 2%. This is largely attributable to AGW. It represents a strong positive feedback to CO2 by approximately doubling the effect of CO2 alone.

The albedo effect is/will be huge and well understood. It is equivalent to the amount of energy taken in by a similar sized area near the equator (say the Sahara- maybe) over the same time.

Admittedly, a significant proportion (by no means all) of this energy will be re-radiated during the winter, but the magnitude of this is one of the things that will need discussion.

This year the arctic from March to September experienced an average sea ice area anomaly of 2,000,000 sq km (peaked at 2.6 million). Over the same period insolation averages ~200W/m2. Thus in the ice free areas the arctic absorbs extra energy at a rate of 160W/m2 (200*.8 change in albedo).

160W/m2 over an area of 2,000,000sq km dilutes to .6W/m2 globally. By comparison doubling CO2 alone leads to a forcing of 3.7W/m2. Including all other feedbacks such as water vapor there is a final forcing probably close to 6W/m2. Thus the decline in sea ice thus far represents only 10% of the total climate forcing for doubled CO2. If sea ice is reduced to zero in September and all other anomalies are doubled, you're still only up to 20%.

And considering this forcing effect is so concentrated regionally, the global forcing is probably actually much less than that because much of the extra energy absorbed would be quickly re-radiated to space (it would be as if we reduced 99% of the earth's CO2 to 290ppm and moved all that extra CO2 over the other 1%... it would not have nearly the effect globally). Possibly as little as half I'd guess. So we're talking about a mere .3W/m2 thus far, up to .6W/m2 if we get completely ice free conditions by late August. That would just be just 5% of the effect of doubled CO2 for current ice conditions, and 10% if the ice anomalies are doubled.

Would have to check peer-review to confirm, but from what I've read surface albedo change is not a huge factor.

[dabize]

I do not doubt for one second your points. I think they are valid.

I just question how much magnitude they actually have. The models HAVE in fact simulated an ice free arctic and show the temp change really doesn;t go haywire. Mostly because the arctic really isn't that big of a space compared to the rest of the globe. There is a lot of talk about all this sunlight hitting an extra 2 million sq km of open ocean rather than ice....yet 98% of the ocean sees sunlight all the time and at a much higher sun angle than the arctic will ever see in our immediate future (perhaps one day the earth will tilt so much that the arctic has a higher sun angle...but irrelevant for this discussion)

This is about the globe, not just the arctic. I would be glad to entertain possibilities of a catastrophic rise in global temperatures if the arctic had seasonally ice-free conditions starting next year. However, this has not been shown to be the case in GCMs....and lets not forget that GCMs have already been over-predicting global temps as it is despite not predicting the ice melt fast enough.

Well, it is a fact that the Arctic summer = tropical in terms of insolation. Don't have the link handy, but it should be easy to verify. I admit I was surprised at that, since I (hitherto) thought that sun angle trumped photoperiod.

So there's no need to tilt the Earth........and we ARE dealing with a large additional number.

And GCMs/GOMs haven't yet had a crack at temperature rises caused by sea ice changes (or the additional heat that they have allowed the Earth to absorb), since they haven't modeled the ice loss that would accompany it.

Again, ice loss should not have not directly resulted in any significant temperature rises yet - it won't until most of the ice is gone relative to baseline. Up until now, open water that is far from any ice has only been generated (in regions heretofore covered by ice) along the periphery and late in the season. It is THIS that is going to change soon.

[skierinvermont]

Well, it is a fact that the Arctic summer = tropical in terms of insolation. Don't have the link handy, but it should be easy to verify. I admit I was surprised at that, since I (hitherto) thought that sun angle trumped photoperiod.

So there's no need to tilt the Earth........and we ARE dealing with a large additional number.

And GCMs/GOMs haven't yet had a crack at temperature rises caused by sea ice changes (or the additional heat that they have allowed the Earth to absorb), since they haven't modeled the ice loss that would accompany it.

Again, ice loss should not have not directly resulted in any significant temperature rises yet - it won't until most of the ice is gone relative to baseline. Up until now, open water that is far from any ice has only been generated (in regions heretofore covered by ice) along the periphery and late in the season. It is THIS that is going to change soon.

See my post above. We're already experiencing average sea ice anomalies in the March-September period of 2,000,000 sq km. If the arctic starts becoming ice free in late August (ZERO sq km, not the normal 1 million sq km definition normally used) that would probably still only double to 4,000,000 sq km anomalies over the period of March to September. And the anomalies would probably be on the lower side (3.5 million) in June during the solstice, while maxing out at 4.5 million (in late August).

The only way you achieve a fairly large global forcing is if the arctic starts becoming ice free in like mid June or earlier. And I don't see that happening this century.

[ORH_wxman]

Well, it is a fact that the Arctic summer = tropical in terms of insolation. Don't have the link handy, but it should be easy to verify. I admit I was surprised at that, since I (hitherto) thought that sun angle trumped photoperiod.

So there's no need to tilt the Earth........and we ARE dealing with a large additional number.

And GCMs/GOMs haven't yet had a crack at temperature rises caused by sea ice changes (or the additional heat that they have allowed the Earth to absorb), since they haven't modeled the ice loss that would accompany it.

Again, ice loss should not have not directly resulted in any significant temperature rises yet - it won't until most of the ice is gone relative to baseline. Up until now, open water that is far from any ice has only been generated (in regions heretofore covered by ice) along the periphery and late in the season. It is THIS that is going to change soon.

This has all been accounted for in GCMs. They have run these with seasonal ice-free conditions. As I said before, you aren't the first one to think of seasonally ice-free Arctic conditions. Yet when they run these models, the temp rise is not anything out of the normal accepted values in peer review. So I'm not sure where you expect this "sudden rise" to come from that nobody else sees.

[ORH_wxman]

The paper takes into account the various factors that contribute to yearly differences in global temperatures.

It showed that the rate of change in global temperature since 1979 is fairly steady through 2010. When you use

similar data you we'll see a the increase across the varying ENSO states.

Is that graph trying to say there is 0.6C of warming under neutral conditions since 1975 with GISS data?

I don't buy that for one second...if anything the warming since 1975 was aided by ENSO, not inhibited by it...and even with that, we warmed about or just under 0.5C since 1975 on absolute measures of GISS.

I am all for discussing the sensitivity, but this probably doesn't help us...and I don't think that graph is accurate.

edit: The graph actually shows closer to 0.5C with that small plot of 2012. So that is pretty accurate. But not sure what those lines are for.

[dabize]

This has all been accounted for in GCMs. They have run these with seasonal ice-free conditions. As I said before, you aren't the first one to think of seasonally ice-free Arctic conditions. Yet when they run these models, the temp rise is not anything out of the normal accepted values in peer review. So I'm not sure where you expect this "sudden rise" to come from that nobody else sees.

It can't be. You can only model something if you know what it is, and the people making models of the evolution of SI changes obviously don't, since they can't hindcast what has already happened. As I said earlier, this isn't just a matter of setting parameters, abolishing the sea ice and seeing what happens (a' la Tietsche et. al.)

BTW, implying (falsely) that someone disagreeing with you is a a ) smartypants upstart or b ) alone in his delusions is obnoxiously close to ad hominem. It is also self contradictory. If I'm not the first, then how can I be alone? Check Bluewave's link.

My viewpoint is quite possibly more widely held than yours - just have a look at Neven's blog for starters. Not that this makes me right. Let's keep the tone here cultured.

[tacoman25]

When you take into account solar and ENSO, the global warming signal remains unchanged.

But the Arctic has warmed rapidly especially during the fall and winter over last decade.

We have also seen a steep decline in spring NH snow cover which has contributed to record

warmth.

We can both probably agree that it would be helpful to run some NH temperature projections

based on these updated initial conditions.

http://iopscience.io...44022/fulltext/

I think what some people may be overlooking is that there is a clear disconnect between what happens in the Arctic and what is happening globally. And this is actually not new: the Arctic has always seen more rapid/extreme changes through different periods observed. It simply has a more variable climate than the rest of the globe and is more susceptible to small changes.

This is apparent as the Arctic has seen relatively extreme climate changes in recent decades, and yet we have seen virtually no change in the rate of warming globally. It remains rather slow, whether you factor out ENSO/solar or not.

Therefore, to draw conclusions about the rest of the globe based on what has happened in the Arctic (or extrapolate warming that has happened in the Arctic to the rest of the NH, as I've seen some people try to do) is probably not the best idea.

[ORH_wxman]

I think what some people may be overlooking is that there is a clear disconnect between what happens in the Arctic and what is happening globally. And this is actually not new: the Arctic has always seen more rapid/extreme changes through different periods observed. It simply has a more variable climate than the rest of the globe and is more susceptible to small changes.

This is apparent as the Arctic has seen relatively extreme climate changes in recent decades, and yet we have seen virtually no change in the rate of warming globally. It remains rather slow, whether you factor out ENSO/solar or not.

Therefore, to draw conclusions about the rest of the globe based on what has happened in the Arctic is probably not the best idea.

This.

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. I'm more interested in how fast we will warm....and what the number is. That is where literally 70% or more of the uncertainty lies in the climate debate. Yet we get sidetracked by an ice calving event in Greenland.

[dabize]

The only way you achieve a fairly large global forcing is if the arctic starts becoming ice free in like mid June or earlier. And I don't see that happening this century.

Why not? That is exactly what recent events suggest will happen, especially considering that the sea ice volume minimum has gone from ~12 km³ to 3+ km³ in the past 10 years.

Do you really think that an entire Arctic full of brine-ridden FYI less than 1 meter thick is going to resist a progressively warming ocean until August for a century? I must say that I don't, but I'm willing to be dissuaded. I'd LIKE to be dissuaded.

I see you agree with me about the bolded point..... Our difference is therefore one of gauging the factors that will determine the rate of change, which seem eminently worth discussing since the result will be a (fairly) large forcing.

[ORH_wxman]

Why not? That is exactly what recent events suggest will happen, especially considering that the sea ice volume minimum has gone from ~12 km³ to 3+ km³ in the past 10 years.

Do you really think that an entire Arctic full of brine-ridden FYI less than 1 meter thick is going to resist a progressively warming ocean until August for a century? I must say that I don't, but I'm willing to be dissuaded. I'd LIKE to be dissuaded.

I see you agree with me about the bolded point..... Our difference is therefore one of gauging the factors that will determine the rate of change, which seem eminently worth discussing since the result will be a (fairly) large forcing.

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.

[dabize]

This.

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. I'm more interested in how fast we will warm....and what the number is. That is where literally 70% or more of the uncertainty lies in the climate debate. Yet we get sidetracked by an ice calving event in Greenland.

Why is it that you and Taco keep overlooking that the Antarctic changes are not affecting and will not affect the global heat budget because they happen in winter, while the Arctic changes are just beginning to cause an entirely quantifiable, large change in said budget?

[ORH_wxman]

Why is it that you and Taco keep overlooking that the Antarctic changes are not affecting and will not affect the global heat budget because they happen in winter, while the Arctic changes are just beginning to cause an entirely quantifiable, large change in said budget?

I'm not sure what you are talking about...the big gains in antarctic sea ice are in September and October when the sun is rising in the south....the large losses in the arctic are in August and September when the sun is setting. The losses in the arctic are greater....but once again you are obsessing over a factor that is really not that large in the scheme of global temperatures. I'm not sure why you keep focusing on the arctic. Why aren't you focusing on the rest of the globe which this thread is about?

[tacoman25]

Why not? That is exactly what recent events suggest will happen, especially considering that the sea ice volume minimum has gone from ~12 km³ to 3+ km³ in the past 10 years.

Do you really think that an entire Arctic full of brine-ridden FYI less than 1 meter thick is going to resist a progressively warming ocean until August for a century? I must say that I don't, but I'm willing to be dissuaded. I'd LIKE to be dissuaded.

I see you agree with me about the bolded point..... Our difference is therefore one of gauging the factors that will determine the rate of change, which seem eminently worth discussing since the result will be a (fairly) large forcing.

I know ORH said he doesn't want this thread to become yet another obsession over the Arctic ice, but I have to address this point: given that we currently see ice in Hudson Bay, much further south, last into July, what makes you think that even if we completely melt out soon (unlikely imo) and have virtually all FYI, that this FYI in the Arctic won't last through most of the summer?

There is simply nothing that suggests we will see all of the Arctic ice melt out by June anytime this century. If there is, please show me the study.

Anyway, let's move on from the Arctic. I know it's the most fascinating to many of you because we've seen so much change there recently, but it's certainly not the end all, be all of climate change.

[ORH_wxman]

I know ORH said he doesn't want this thread to become yet another obsession over the Arctic ice, but I have to address this point: given that we currently see ice in Hudson Bay, much further south, last into July, what makes you think that even if we completely melt out soon (unlikely imo) and have virtually all FYI, that this FYI in the Arctic won't last through most of the summer?

There is simply nothing that suggests we will see all of the Arctic ice melt out by June anytime this century. If there is, please show me the study.

Anyway, let's move on from the Arctic. I know it's the most fascinating to many of you because we've seen so much change there recently, but it's certainly not the end all, be all of climate change.

The arctic is fascinating because its the only region that is warming a lot in the past decade plus....and I actually find it fascinating too. But not on the level of predicting global temps because of it.

[tacoman25]

Why is it that you and Taco keep overlooking that the Antarctic changes are not affecting and will not affect the global heat budget because they happen in winter, while the Arctic changes are just beginning to cause an entirely quantifiable, large change in said budget?

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.