Antarctic Ice Melting from Warm Water Below

If you look further up in comments you will see that I said exactly that - doubling of CO2 and 40 years. Anyone that Hansen commented to has also changed it as he wished. Which leaves us with 2 questions really, that of doubling of CO2 and that of speculation. First lets look at doubling of CO2 and if it would drastically change the facts on the ground in NYC. It is not as you say 10%, but normally we talk about the doubling from industrialization 290 ppm in 1850. The currently adjusted value is 393ppm, and should be around 420 ppm in 2028, when the prediction is due. You don't need to be very good with math to know that 420 is less than 560 (double), but you do need to be a little stronger to model. CO2 doesn't melt ice at all in these low concentrations, but temperature does which means we need to examine temperature affects. The radiative forcing of CO2 is logrithmic, and amounts to about 1 degree C per doubling of concentration, additionally there is feedback that accounts for perhaps anouther 2 degrees (estimates very but this is a popular consensus number that hansen uses.) . This means the direct affect so far is about 0.5 degrees and feedback so far is anouther 0.3 to make a total 0.8 degrees we measure since industrialization. This feedback is a slow moving thing. 560ppm would give us another 0.5 degrees over today. There is that feedback though and temperatures will rise in Greenland at a greater rate than say somewhere around the equator. One big slow down in thermal inertia in the oceans, that extra heat is not going to do much in 40 years there. The other feedback is change in albedo, and here a speed up in ice melt would actually be negative feedback as more sea ice would provide negative instead of positive feedback in such a short period of time. We can calulate most things but this little bit of extra heat would not greatly speed up the glaciers moving to the sea. It would increase thermal expansion and surface melt. Altogether maybe another 0.050 meters or 2 inches as an outside estimate. Not even Hansen today believes glaciers can speed up that fast, and made a new fast theory in 2005 about exponetially increasing rate. Here the extra heat would do less than those 2 inches.

The second point you make is he was only speculating, because some reporter backed him into a corner, or some such thing. The scientist that renounced the 2035 glacier melt did say this, and I would have prefered that response from Hansen. It gets followed up with "I don't have enough information for a good estimate". Unfortunately the 5 meter rise is also pure speculation on Hansen's part, which is why I brought up this prediction.

IMHO I certainly did not quote anything out of context, I simply didn't added that doubling bit on a second response. This was to show the newer speculation by hansen also needs some data back up, not just his authority. His estimate is an outlier without data to back it up.

 

The concentration at the time of the hypothetical quesiton was about 340, doubled would be 680. In his 1981 paper (based on work from 197981) Hansen had considered the temp impacts of a 600, which is a mean temp change of 2.5 to 3 degrees. (http://www.atmos.washington.edu/~davidc/ATMS211/articles_optional/Hansen81_CO2_Impact.pdf)
And at the times that was one of the best models of CO2-> temperature impact. (I don't know where you get your 1 degree C per doubling, IPCC has a doubling from industrial (i.e. 580 you mentioned) producing a rise of 1.5 to 4.5C).

That paper also provided a reason to consider the west Antarctic sheet at risk to a full melt if there was a 5C rise. So if in a back of the envelope the 680 levels could produce that 5C shift, which is within the range of estimation errors given the models of that day, it could by the best models of the day lead to a 5-6m rise.

We have learned more about the feedback cycles that slow things down since 1980, and its easy to go look back and say why some of that work was wrong. But for what was known in the day, it was not that bad an off the cuff estimate.

With respect your suggested mechanism, Sea ice at current levels would have minimal impact on the albedo effects as the area would be a small fraction of clouds and a complex scattering function (most light is scatters sideways not back up). (Sea ice would be an impact only if it grows significantly-- towards the tropics). At current levels the cloud impact is the larger feedback cycle on aldbeo. However clouds have both a upward reflective effect (cooling) and downward reflecting (warming) effect.


Did not mean to imply you quoted out of context, but rather many of the sources in the media and some in the field are in a an attempt to discret his work.

Hanson's recent theories are well reasoned, e.g. http://www.columbia.edu/~jeh1/mailings/2012/20120508_ClimateSensitivity.pdf.
but because of the model sensitivity and exponential impact, our current data is simply insufficient to determine the parameters well enough to disprove, or prove, hansen's model.

 

1 degree comes from the simple physics of it all, if you add in the theoretical 2 degrees of feedback it adds up to 3 degrees C, exactly near the center of the range. The number may be different, the feedback is slow which along with natural variation causes debate. Alley calculated 2.8 degrees from historical correlations, but this would be ghg leading temperature, and most of those are temperature leading ghg. Over land air temperatures do rise quickly with feeback, but when talking glaciers the ice and sea will react more slowly. If we assumed this extra 0.5 degree of direct warming occured 50 years ago then perhaps another 1 of feedback would be in the system, but end loading it will not cause a great change. Use 1.25 degrees for the 3x full impact of 420 to 560 ppm CO2 if you want, it will not greatly change the melt. Doubling from the industrial revolution is the common start point of these discussions, and is around the level that a BAU (business as usual) case would be if sequestration was not as high as we find it to be today. CO2 is being generated at a BAU case and follows closely with the IPCC A2 scenario. If it was asking about doubling in 40 years he should have said that isn't feasible.

Research from the ice cores shows a 6 meter to 10 meter higher sea level in last interglacial at temperatures just about 1 degree higher than today. There should be enough ghg gas in the system to do that now, and some have speculated at a 25 meter rise. The problem with the speculation was not sea level rise, but the speed. The speed that the ice would need to accelerate to march into the sea and melt was not thought about at all.

Currently melting sea ice is theorized to be responsible for some local warming in the artic and antartic. A great expulsion of sea ice would reverse this providing negative feedback. This is one of those pesky limiting factors. Hanson acknowledges it in a paper in 2009, but seems to completely ignore it in the 5 meters for 2100 shown in the chart. The chart and 5 meters are illustrative in the papers, he never mentions them as a prediction, otherwise they would have been subject to peer review. The chart implies in the last decade he has ice melt causing a 3 meter rise, with only positive feedback. Which leads us to 6 meters in the next decade, and 12 in the next. That yields 21 meters in 30 years and another 24 coming, not a likely scenario. The chart is speculation on what is possible, not a scientific idea of what is likely.

I was only commenting on the 5 meter outlier on sea level rise by 2100. Pfeffer at the University of Colorado has done some excellent work pegging it at likely less than a meter but possibly as high as 2 by 2100. He does use modelling of glacier movements in his work. There is no way to disprove Hansen's theory of decadal doubling of ice melt, but there is a great deal of data that contradicts the model.

 

There are studies which contribute LIA to reforestation due to black plague in Europe and small pox devastation in New World due to Columbus "discovery"..

 

There are 3 .5 MILLION underwater volcanoes.
This accounts for 80% of the Earths volcanism.
Volcanic activity is at a high point due to an increase in the Suns flare activity.
Do you suppose these could this cause any temp rise ?

Huge Underwater Volcanoes Discovered Near Antarctica | OurAmazingPlanet.com

 

^according to some people,, (see also Corbyn?)

Icarus

 

No discusion of atmospheric energy balance would be complete without volcanos. Or volcanoes!

If you start here

Volcanic Gases and Climate Change Overview

you will at least have some basis for evaluating affinity websites: Iceagenow, etc. There are too amny others to list.

The volcanic emissions are not simple. There is CO2, and in terms of infrared energy balance it is no different than CO2 from coal or oil. Different mix of stable carbon isotopes though, and this contributes to the clear understanding that volcanic CO2<< fossil-fuel burn CO2.

Other volcanic emissions have cooling effects. If they get no higher than the troposphere, they rain out in weeks. If they are blasted into the stratosphere they can cool for years. See "the year without summer" for drama.

Undersea volcanos' ash cannot enter the atmosphere. Their CO2 could enter the atmosphere if it got past 'the gauntlet' of marine photosynthesizers. As the oceans remain net carbon sinks, we can know that this is not happening (now).

Whether there is an ongoing increase in volcanic activity sounds to me like a test for data. For 'small to medium' eruptions, I suppose that the data history is short. For big eruptions, the record is probably quite complete for about 1000 years. Longer than that, there are sulfate 'spikes' in the ice cores that are reasonably well dated. Including that whacking Toba event about 74 thousand years ago. My personal favorite because of itsapparent (mitochondrial) effect on the human population.

So here again there is an opportunity to test the hypothesis whether (at least the large) eruptions are significantly correlated with some aspect of the solar cycle.

From another affinity website

Prison Planet.com &raquo; Can Solar Activity Cause Earthquakes, Volcanoes and Extreme Weather?

we can learn that Corbyn expects more earthquakes and volcanoes at solar minima. Now of course, the solar cycle is ramping up again. Should be tamping them down then, eh?

In that sense, post#85 confuses me. If the prediction - mechanism relationship can go every which way, I cannot follow gleefully along. A test of hypothesis with historical and paleo-data would be much more satisfying. Compelling. Truthy.

 

Im actually referring only to the effect of volcanic geothermal warming of the ocean directly under an ice sheet which is melting from warm water.Heat from a underwater volcano would rise directly to the ice sheet.

Interesting article ,thanks for the link.
I think the author is a bit confusing.When he quotes Piers about "minima" .
My take (which could be totally wrong), is that current Solar cycle 24 is a relatively very low sun spot activity Solar cycle and that is what the author is referring to as "minima".
The Sun is now at maximum phase and recently Solar flares are becoming massive.With more higher energy bursts than in a normal (higher # of sunspots)solar cycle.
Soon the Sun will enter its minimum phase and there will be no or few sunspots.
At the minimum phase ,my understanding is that there should be less earthquakes.
The Solar minimum we are entering is in a period of such low sunspot activity that many astrophysicists are predicting a mini ice age beginning in a year or 2 from now, and lasting 30 years.