Skip to comments.Why melting polar ice is not a threat
Posted on 02/18/2007 7:26:06 PM PST by Exton1
Why melting is not a threat
While today's balance between the icecaps and global sea level has been relatively steady since about 1000 B.C., it would be careless to assume that this is the Earth's natural state and that it should always be this way. What could happen to climate naturally in the next few thousand years? If the Earth continued to warm and break from ice age conditions, some of the remaining ice caps could melt. On the other hand, climate might swing back into another ice age. (In fact, some of the environmentalists now worried about global warming were worried about another ice age in the 1960s and 1970s.)
In either case, such a change in climate would take thousands of years to accomplish. Note that it has taken 18,000 years to melt 60% of the ice from the last ice age. The remaining ice is almost entirely at the north and south poles and is isolated from warmer weather. To melt the ice of Greenland and Antarctica would take thousands of years under any realistic change in climate. In the case of the East Antarctic Ice Sheet, which accounts for 80% of the Earth's current ice, Sudgen argues that it existed for 14,000,000 years, through wide ranges in global climate. The IPCC 2001 report states "Thresholds for disintegration of the East Antarctic ice sheet by surface melting involve warmings above 20° C (20 C = 68 F)... In that case, the ice sheet would decay over a period of at least 10,000 years." The average temperature in Antarctica is a crisp, or rather, biting -49 C. The IPCC is the United Nations' scientific committee on climate change; its members tend to be the minority that predicts global warming and its statements tend to be exaggerated by administrators before release. Given that the IPCC tends to exaggerate the potential for sea level rise, it is clear that no scientists on either side of the scientific debate on global warming fear the melting of the bulk of Antarctica's ice. Consider also this abstract of an article by Jacobs contrasting scientific and popular understanding:
A common public perception is that global warming will accelerate the melting of polar ice sheets, causing sea level to rise. A common scientific position is that the volume of grounded Antarctic ice is slowly growing, and will damp future sea-level rise. At present, studies supporting recent shrinkage or growth depend on limited measurements that are subject to high temporal and regional variability, and it is too early to say how the Antarctic ice sheet will behave in a warmer world. 
This statement alludes to the significant point that the Antarctic ice cap appears to currently be growing rather than shrinking. In fact, were the climate to warm significantly in the next few centuries (not a certain future, but supposing it happened), current models suggest that Antarctica would gain ice, with increased snowfall more than offsetting increased melting.
How much concern should we have about the 20% of world ice outside the East Antarctic Ice Sheet? Some sources have recently discussed the "possible collapse" of the West Antarctic Ice Sheet (WAIS). It is suggested that this sheet (about 10% of Antarctic ice) could melt in the "near term" (a usefully vague phrase) and raise sea level 5 to 6 meters. Current understanding is that the WAIS has been melting for the last 10,000 years, and that its current behavior is a function of past, not current climate.  The abstract of an article by Alley and Whillans addresses this:
The portion of the West Antarctic ice sheet that flows into the Ross Sea is thinning in some places and thickening in others. These changes are not caused by any current climatic change, but by the combination of a delayed response to the end of the last global glacial cycle and an internal instability. The near-future impact of the ice sheet on global sea level is largely due to processes internal to the movement of the ice sheet, and not so much to the threat of a possible greenhouse warming. Thus the near-term future of the ice sheet is already determined. However, too little of the ice sheet has been surveyed to predict its overall future behavior. 
Similarly, recent stories have periodically appeared concerning the potential receding of the Greenland ice cap. Two points may be made regarding current understanding here. First, there is considerable disagreement as to the current rate of net ice cap loss--or even if there is net loss versus net gain. Second, even with temperature increases far greater than the dubious predictions of the IPCC, models indicate that Greenland's ice cap would take 2,000 to 10,000 years to disappear.
Some discussion of the concerns about near term sea level rise may be found in Facts and figures on sea level rise. The predictions that have been made for ice cap melting in the next century rely mostly on melting of glaciers in mountain regions, not melting of the polar ice caps. Even the pessimistic models cited by the IPCC tend to predict an increase in the volume of the Antarctic ice cap with warmer temperatures due to increased snowfalls. In general temperature changes of a few degrees do not seem to be sufficient to begin to melt the polar ice caps, particularly the Antarctic ice cap.
I just watched a program on the International History Channel describing a Saxon sea port of around 1000 AD. The archeologists are now able to examine this area because the sea level, at least at this part of England, is about 6 - 10 feet lower than it was in the days when the Saxons were able to sail into the port. I wonder where the water went. There is no river at this place to have silted up the harbor. Could it be we are still locked in the final stages of an ice age and the Earth is just returning to normal conditions?
In case you wondered what that looks like to Florida:
Time to move back to New York, Yankees...
This sea would contain the melt-off from most of the Greenland glaciers and turn an environment viturally void of life into a vibrant source of sea life and shoreline villages which would support fishing and agriculture.
The main downside is that it wouldn't give the global warming alarmists control of first world economies-- which is their real objective.
It's nice to see something that discusses the lag time for ice sheet response, but there are a lot of missing points in this article, too. One very important point, for example, is whether we have a shift from a dry-bed to a wet-bed sheet...the rate of advance of a wet-bed sheet is higher, which leads to ice thinning and more rapid collapse (greatly oversimplifed).
Though I often say words that are nearly verbatim what you have posted, it's really more true that "normal" is not a steady state. Climate is ever-changing, IMHO.
Reminds me of the SNL clip about the attacks on tourists:
"We want to remind you that these recent outbreaks of crime have all taken place in SOUTHERN Florida."
Have you run the calcs on that?
That much of florida is within 15 feet of sea level?
Does that mean a 20-foot storm surge would wash out the entire southern tip of the state?
Ice sheets are in the ocean anyway so melting makes no difference its just ice cubes in glass of water.
Its an improvement...Key West and Miami.
This does not quite seem believable.
Using data mostly from Wikipedia:
Water covered area of planet Earth = 361,126,400 km²
Ice covered area of Antarctica = 13,720,000 km²
Therefore 10% of Ice covered area of Antarctica = 1,372,000 km²
Ratio = 263.2 to 1.0
Density of glacier ice compared to sea water = 0.867
Therefore, to raise the sea 6 meters, means the 10% of the ice shelf effectively has to have ice 300 meters thick, almost 1,000 feet thick.
Perhaps 300 meters is the right thickness. But if all of a sudden an ice sheet weighing ALMOST FIVE TRILLION POUNDS slid into the ocean, I think a tsunami would be the bigger immediate threat.
Feel free to check my math.
I think it's time to buy some of that beachfront Orlando property.
"Thresholds for disintegration of the East Antarctic ice sheet by surface melting involve warmings above 20° C (20 C = 68 F)... In that case, the ice sheet would decay over a period of at least 10,000 years." The average temperature in Antarctica is a crisp, or rather, biting -49 C.
Ran into an interesting little study concerning the termination of ice ages that falls right into line with this. Seems the thresholds to terminate the deep glacial ice ages can not be triggered by CO2 concentrations found for those conditions in ice core studies, it take more than 500 times the CO2 present in today's atmosphere to terminate deep ice ages and cause melting of glacial ice.
High levels of atmospheric carbon dioxide necessary for the
termination of global glaciation
Raymond T. Pierrehumbert
Department of the Geophysical Sciences, The University of Chicago,
Nature Vol 429 10 June 2004
The possibility that the Earth suffered episodes of global glaciation as recently as the Neoproterozoic period, between about 900 and 543 million years ago, has been widely discussed13. Termination of such hard snowball Earth climate states has been proposed to proceed from accumulation of carbon dioxide in the atmosphere4. Many salient aspects of the snowball scenario depend critically on the threshold of atmospheric carbon dioxide concentrations needed to trigger deglaciation2,5. Here I present simulations with a general circulation model, using elevated carbon dioxide levels to estimate this deglaciation threshold. The model simulates several phenomena that are expected to be significant in a snowball Earth scenario, but which have not been considered in previous studies with less sophisticated models, such as a reduction of vertical temperature gradients in winter, a reduction in summer tropopause height, the effect of snow cover and a reduction in cloud greenhouse effects. In my simulations, the system remains far short of deglaciation even at atmospheric carbon dioxide concentrations of 550 times the present levels (0.2 bar of CO2). I find that at much higher carbon dioxide levels, deglaciation is unlikely unless unknown feedback cycles that are not captured in the model come into effect.
Just to get an idea of what 550 times current CO2 is in comparison to levels found in geological history:
Late Carboniferous to Early Permian time (315 mya -- 270 mya) is the only time period in the last 600 million years when both atmospheric CO2 and temperatures were as low as they are today (Quaternary Period ).
Temperature after C.R. Scotese
CO2 after R.A. Berner, 1994
- There has historically been much more CO2 in our atmosphere than exists today. For example, during the Jurassic Period (200 mya), average CO2 concentrations were about 900 ppm or about 2.5 times higher than today. The highest concentrations of CO2 during all of the Paleozoic Era occurred during the Ordovician Period, exceeding 6000 ppm -- more than 16 times higher than today.
- The Carboniferous Period and the Ordovician Period were the only geological periods during the Paleozoic Era when global temperatures were as low as they are today.
To the consternation of global warming proponents, the Late Ordovician Period was also an Ice Age, with CO2 concentrations nearly 15 times higher than today-- 5500 ppm. According to greenhouse theory, Earth should have been exceedingly hot. Instead, global temperatures were no warmer than today. Clearly, other factors besides atmospheric carbon influence earth temperatures and global warming.
Yes. Most of southern florida is lakes and grasslakes, or swamps.
Does that mean a 20-foot storm surge would wash out the entire southern tip of the state?
Storm surge is a factor of coastal shape and distance from the coast. Hurricane Andrew (cat 5) hit with a 7-10 foot storm surge and inundated the coast where it hit eastern florida. Coasts along the upper rim of the Gulf of Mexico can get worse surge because of how the coast focuses water, but it's also higher ground right from the coast in most of the Florida panhandle (excepting the lowland swamps in the river basin north of Port St. Joe).
Don't confuse north polar ice with the ice sheets. Most of the ice (90%) is in ice sheets several miles thick over Antarctica. The reason the Greenland ice sheet is considered significant is again because it rests on land, not already in the water, and its flow into the Gulf Stream is a factor in that currents thermally driven flow. Significant alteration of the Gulf Stream's flow has importance to Europe because, if you look at a globe, their location farther north would have an otherwise cooler clime.
Note: this topic is from February 18, 2007. Thanks Exton1.
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