TCS Daily

Ice Storm

By Patrick Michaels - February 17, 2006 12:00 AM

The latest issue of Science contains a paper by Eric Rignot and Pannir Kanagaratnam claiming that glaciers along the periphery of Greenland are melting at a rapidly increasing rate. Another paper on this subject was published by Science just last year. Ola Johannessen did not consider direct ice lost by glaciers into the ocean but instead only focused on elevations changes. Johannssen showed that increasing snowfall in Greenland was leading to greater ice accumulations than had previously been measured and this was acting to slow Greenland's contribution to sea level rise. It was conspicuously ignored in this new report.

The new paper uses radar measurements from satellites and concludes that there has been a widespread acceleration in the calving and loss of Greenland's glaciers during the past 10 years. The authors calculate that Greenland's glaciers were calving about 56 cubic kilometers of ice (km3) (give or take 30 km3) per year back in 1996, and that during the past 10 years, the volume of ice loss had risen to 167 km3 per year (give or take 40 km3). And this was just from glaciers dumping ice directly into the ocean (as opposed to melting ice).

Additionally, they speculated that snow and ice over other parts of Greenland are melting and the water is flowing into the ocean. Citing other work by Hanna et al. (2004), Rignot and Kanagaratnam figure another 35km3 in 1996 and 57 km3 in 2005 of ice loss occurred from surface melting bringing the total annual loss volume to 91 km3 in 1996 and 224 km3 in 2005.

This water and ice input leads to a sea level rise of 0.23 ± 0.08 mm/year in 1996 growing to 0.57±0.1mm/year by 2005. Not surprisingly, the reason that is given -- or at least presumed -- for the melting ice and the rising seas is that temperatures are going up because of global warming.

Why would Science publish this paper with no reference to Johannessen's earlier paper showing that Greenland is accumulating ice at a rate of about 5.4±0.2cm/year? Johannessen even used data from some of the same satellites. What's more, Johannessen used real data and Hanna et al., cited by Rignot, used a model of surface melt.

Consider what would have happened had the latest study included the ice and snow gains observed by Johannessen (and ignored the losses modeled by Hanna et. al.). Johannnessen's increase of 5.4cm/year averaged over Greenland converts to about 75km3/year. Rignot and Kanagaratnam could have subtracted Johannessen's gains. If they had done so, the total volume of ice loss from Greenland would only have become positive during the last 5 years, totaling 17km3 in 2000 and 92km3 in 2005. This translates to a sea level rise contribution of 0.04mm in 2000 and 0.23mm in 2005 -- values much less dramatic than those they published.

And what does all of this have to do with global warming? A look again at real data is instructive.

Temperatures fluctuations around Greenland are part of a phenomenon -- known as the Atlantic Multidecadal Oscillation (AMO) -- that connects with temperature changes further south, in the hurricane formation regions of the tropical Atlantic. The AMO goes through, as its name suggests, multidecadal swings from being cooler than normal both in the ocean around Greenland and in the tropical Atlantic, to being warmer than normal in both places. And modelers have suggested that the AMO has been part of the natural system for at least the past 10-15 centuries (see here).

When the AMO is in its positive (warm) phase, the Atlantic hurricane seasons become active with more and stronger storms; and, apparently, Greenland's glaciers flow faster and dump more ice into the ocean.

When the AMO is in its negative (cool) phase, hurricane activity in the Atlantic is suppressed and Greenland's glaciers flow slowly. The AMO changed from negative to positive in 1995 -- and since then hurricanes have become very active and glacier output has been accelerating. There is no need to invoke global warming for any of this.

Many of the world's foremost experts on hurricanes argue emphatically that it is the natural oscillations of the AMO -- not anthropogenic climate change -- that is primarily responsible for the enhanced Atlantic hurricane activity during the past decade or so (see here). And since the AMO ties together the sea surface temperatures in the tropical Atlantic with those around Greenland, the same argument applies to Greenland's glaciers.

Figure 1a shows the regions in the Atlantic Ocean that are most related to the AMO, and Figure 1b shows the AMO index for the past century.

Figure 1a. The relationship (correlation) between Atlantic sea surface temperatures and the AMO index; Figure 1b. The history of the AMO index since 1870 (source: Goldenberg, et al., 2001).

Figure 2 is the 20th century temperature history from the southern end of Greenland, from the United Nations' Intergovernmental Panel on Climate Change. Notice how similar it looks to the AMO history in Figure 1b. Also notice that both the AMO and Greenland temperatures were generally higher in 1930s and 1940s as they are today. We know that Atlantic hurricane activity has high back then, we can only assume that glacial flow rates were up there as well.

Figure 2. Temperature history from the southern portion of Greenland (source:

So what we have here are two stories making a lot of headlines -- Greenland is melting and hurricanes are strengthening. Both things are true. And, again, looking at real data it is apparent that at this time they are both part of a natural cycle that has been going on for thousands of years.


Goldenberg, S., et al., 2001. The recent increase in Atlantic hurricane activity: Causes and implications. Science, 293, 474-479.

Hanna, E., et al., 2005. Runoff and mass balance of the Greenland ice sheet, 1958-2003. Journal of Geophysical Research, 110, doi:10.1029/2004JD005641.

Johannessen, O.M., et al., 2005. Recent Ice-Sheet Growth in the Interior of Greenland. Science, 310, 1013-1016.

Knight, J.R., et al., 2005. A signature of persistent natural thermohaline circulation cycles in observed climate. Geophysical Research Letters, doi:10.1029/2005GL024233.

Rignot, E., Kanagaratnam, P., 2006. Changes in the velocity structure of the Greenland ice sheet. Science, 311, 986-990.



Enough data
There is an electronic circuit model called ****e that lets you virtually test circuits before you build them. EE's are split down the middle on it. Some love it, some hate it.

Bob Pease once reported that a user asked for help because his circuit was oscillating when it shouldn't.

After checking the circuit diagram the user sent, Bob asked the user to measure the level of oscillation at some points in the circuit with a scope. The user replied that the real circuit wasn't oscillating, "but ****e says it should oscillate."

To paraphrase the C&W song, "That's my model and I'm sticking to it."

Sure is lucky that this is just an academic issue...
I mean, it's not as though there would be actual consequences from ice caps melting. So most of the professors say one thing and a few say they're wrong. Who cares? Wha's the worst that can happen?

Piled higher and Deeper
Just wondering what happens as more ice builds on Greenland, would that apply more downward force adding a bit more push to the ice on the edges accelerating the ice flows into the sea?

Erik the Great
Apparently early in the last millennium the Vikings settled and farmed the area they named Greenland. Some say they named it such in a fit of sarcasm. Others say that since there is evidence they farmed it, they must have meant the name to be descriptive. After two or three centuries they abandoned the settlements as the temperatures had declined to a point where it was too cold.

At the end of WWII, a US Army Air Corps group had to ditch several planes (I believe they were B26s) because of bad weather and crash landed on ice in Greenland. Most of the crewmen were rescued but the planes were abandoned. In the mid-'90s the planes were located and it was determined they had been buried in over two hundred feet of ice.

This type of buildup of ice occurred in approximately 40 years. Amazing how quickly circumstances can change isn't it?

I would have thought a defense of the National Academy of Sciences would be in order from you. Other than that I would say to stay away from these issues since you don't have very much to contribute.

I don't believe that the filters should be set to find offensive phrases that occur inside other words.

The word that got filtered above is s*p*i*c*e. A well known program that's been in use since at least the 70's. Also a category of chemicals known to modify the flavor of foods.

As the article shows, the melting that is occurring is the result of a natural cycle. In a few years the cycle will reverse, so will the melting.

It's only those who don't know what they are talking about (you for example) who try to make a big deal about it.

Since the last warm phase of this cycle didn't kill all of humanity, why should we assume that the current one is going to?

Don't confuse them with facts.

There are lives in the balance
No matter which side you take, if you're wrong on this one, people are going to die. If you are whistling past the graveyard, storms, floods, loss of food crops will kill people all over the world. If you call the wrong crisis or call a crisis when there isn't, the foregone growth leads to higher deaths from poverty, slower rates of innovation (from all that research money diverted to a blind alley), and a lower worldwide economic growth rate.

This is by no means an academic exercise and both sides can credibly claim the moral high ground here by saving lives.

Why worry?
Michaels is in the distinct minority on this issue. the NAS represents the views of the vast majority of scholars in the field, and Science is (with Nature) the premier peer-reviewed publication for environmental issues.

But why worry about this stuff? I mean, it's just scientists disagreeing. What possible effect could this have on your life?

As far as "contributing" -- I'm not an expert. I do think it's bizarre when other people who aren't experts are certain --not just suspect, but are certain -- that human caused climate change is ridiculous, a scam, etc. They wouldn't tell their doctor how to operate, or an airplane designer how to shape a wing, but on this subject, they know it all. But that's not you, is it?

and you know this how?
what the people who study this for a living have found out is that this is not a natural cycle, but one precipitated by human activity.

You don't believe it? Fine. But that's what the research says. And all your noisemaking won't change it.

Didn't farm it.
They raised cattle. Unfortunately, they raised too many cattle, cut down too many trees and refused to learn to hunt seals and wouldn't fish. When it got colder, they built churches instead of ships and starved in a classic example of how not to cope with change.

of course: except
the 'foregone growth" is a red herring. All kinds of "no regrets" scenarious have been proposed. The costs of changing the energy mix are balanced by benefits: new industries, new jobs.

But here's the thing: if the NAS and other experts are right, we're running out of time to do something about it. The longer we do nothing, the harder and more difficult action will be.

why do you lie eric?
Some of the people who study this believe as you do.
The vast majority do not.

Can you dispute the graphs given in this article, or do you just wish to keep screaming your usual mantra?

even the IPCC
has come around to the belief that any warming will be at the lowest, barely noticeable end of the scale.

Why don't you keep up with the science for once?

eric is changing his story ... again
I thought you have been claiming that the great hockey stick has proven that the world had a constant, unchanging temperature until the last 50 years?

Now you are admitting that Greenland was once warmer than it is today?

Ummpteenth time: I'm not an expert, and neither are you.
If Michaels wants to take issue with the article in Science, he should do so according to academic protocols, in a letter to Science that the authors of the study can dispute. Publishing it here may be impressive to people who couldn't find their nose with a handkerchief, but proves nothing about the issue.

As far as "the vast majority do not:" if this were true, the National Academy of Science would have vastly different publications and conclusions.

The fact that you can' make the simpleist assertion without affiixing words like "lie" discredits you each time you do it.

"any warming will be at the lowest, barely noticeable end of the scale."

Please document this assertion -- where did IPCC say this?

I said this when?
You don't understand the hockey stick, you don't understand what average global temperature means, and you have no back up for anything you say. But you expect to be taken seriously.

"Johannssen showed that increasing snowfall in Greenland was leading to greater ice accumulations than had previously been measured and this was acting to slow Greenland's contribution to sea level rise. It was con****uously ignored in this new report."

Why was this report ignored?
Does Science have an agenda to push?

No Subject
it was probably ignored because in that actual Johannssen paper, that this TCS author counts on you not reading, are these statements:
1)...the NAO can explain about three-quarters of the surface elevation changes, leaving us to speculate on
other factors. (pg 1015)


2) A modeling study.....consistent
with our findings, which implies that
perhaps a quarter of the growth may be caused
by global warming in Greenland in our
observation period." (pg 1015) - due to increased precipitation.

they wrap it up with: "It is conceivable that pronounced ablation (e.g., 10, 11) in low-elevation marginal areas could offset the elevation increases
that we observed in the interior areas."

and conclude that "..the 11-year-long data set
developed here remains too brief to establish
long-term trends" (pg 1015)

i'll admit to not reading the rignot and Kanagaratnam paper fully, but they seem to compliment each other in some respects. The Johannssen paper states very specifically that they observered ablation below 1500 m in elevation, which is then quantitfied.

Also worth noting, after a skim of Rignot and Kanagaratnam. Their study showing these decrease in elevations uses data from 1996 to 2000.

Johannessen et al show show an overall elevation increase between 1992 and 2003. However, the bulk of this increase came between 1995 and 1996. 1996 and on showed an increase in areally average ice elevation across their study. see fig 3, page 1014.

Johannessen et al show a general DECREASE in ice elevation from 1996 to 2003 (fig 3.) the magnitude of this decrease is not as great as the increase, so the overall trend in the study period is an increase.

correction correction
ignore everything i said about the time element of the two studies, i read the graph incorrectly. the rate of increase decreased between 1996 and 2003, not a decrease in ice elevation. no edit function here apparently.

Not "settled" in the least
Check this out...

I find it funny that you claim not to be an expert and yet you throw in your lot with a small portion of scientists who believe as you do.

The NAS does NOT represent the views of a "vast" majority. Perhaps you could provide some data that proves this? It is a tactic you seem quite fond of.

The chicken-littles of the world have been wrong before: ice ages, oil running out by 2000, and of course, the 20 billion people on Earth by the year 2000. Some of us are old enough to remember that scientists can be quite wrong.

Thick Ice, Thin argument
"Why would Science publish this paper with no reference to Johannessen's earlier paper showing that Greenland is accumulating ice at a rate of about 5.4±0.2cm/year?.... Johannessen used real data and Hanna et al., cited by Rignot, used a model of surface melt. "

Science doubtless noticed, as Michaels perhaps has not, that Johannesens references inform us that isostasy has forced much of the land surface of Greenland beneath the ice below sea level, so the increased ice thickness Johannessen relates is unlikely to see the sea for as many eons as isostatic rebound takes - witness what has been happening in Hudson's bay, the White Sea, and the Baltic since they were unburdened by the Ice Age's retreat .

One expects a higher standard of dissimulation from Pat-but then, he is discoursing in the frozen wilds of the No Peer-review Zone.

"Consider what would have happened had the latest study included the ice and snow gains observed by Johannessen (and ignored the losses modeled by Hanna et. al.). "

Consider it indeed- the Science authors would be gulty of gratuitously injecting upwards of tenthousand years worth of anachronism into a discussion of contemporary climate change. They are innocent- what about Pat ?

"Johannnessen's increase of 5.4cm/year averaged over Greenland converts to about 75km3/year. Rignot and Kanagaratnam could have subtracted Johannessen's gains. If they had done so, the total volume of ice loss from Greenland would only have become positive during the last 5 years"

Ye cats, who gives either end of rat about an extra 750 cubic kilometers of ice stuck in the middle of the millions sitting atop central Greenland if any peripheral percentage ends up sloughing off into the drink- I hope Pat has a good immersion suit, because he's skated out miles from scientific commonsense on very thin rhetorical ice.

Ice Caps
Over the last 500 million years, the earth has had no ice caps for a longer time than it had them (see the link to the Shaviv and Veizer paper below). It's a fairly regular cycle with a length of about 140 million years. There have been four cold phases, during one of which there is no direct evidence that ice caps were present. Needless to say, during the warm phases it was a LOT warmer than it is today. Life on earth did not cease during the warm phases. There is little evidence of a correlation with CO2 levels (Veizer and Shaviv again, that data was NOT successfully challenged). At the present, we are probably past the coldest point of the long term cycle. Note that at least one of the CO2 concentration reconstructions shows CO2 levels up to about 20 times higher than current levels. In fact, all of them show that the current level is about as low as it has EVER been.

Of course, there are cycles within cycles.
We have times of increased ice coverage called ice ages that last about 100,000 years followed by interglacials that last about 20,000 years. Antarctic ice core proxy temperatures derived from hydrogen isotope ratios go back about 500,000 years. They longest record, which was recently published (see here for an interactive graph of the temperature data: ), includes about four cycles. This particular interglacial is, so far, below average in temperature. This also means that anyone who tells you that this is the warmest it has been in the last 70,000 to 80,000 years is merely stating a truism that has no relevance to the anthropogenic global warming debate because the last interglacial ended about 120,000 years ago. The ice core also showed that changes in CO2 concentration in the atmosphere lagged temperature changes in both directions by about 2000 years.

The cycle of ice ages and interglacials seems to correlate with periodic variations in the orientation of the earth's axis during it's orbit around the sun. Google "Milankovich cycles" for more info. There is no accepted explanation, as far as I know, for the 140 million year cycle.

A recently proposed hypothesis ( ) to explain the long term cycle involved cosmic rays from the galactic core modulated by the rotation of the galaxy. Variations in cosmic ray flux are theorized to cause changes in cloud cover because they create ions and these should nucleate the formation of water droplets as they do in cloud chambers that were used for high energy physics research and thus affect the earth's temperature. This hypothesis is based on satellite measurements of cloud cover and cosmic ray flux which is modulated by the solar magnetic cycle ( Unfortunately, the long term record of cosmic ray flux used by Veizer and Shaviv in their paper has been successfully challenged so that it cannot be used to prove or disprove this theory. When the big accelerator at CERN gets back in operation they may be able to run some experiments to shed more light on this hypothesis.

For those who are interested in a compendium of abstracts and comments on peer reviewed scientific journal articles that cast doubt on the current global warming 'consensus', I highly recommend .

A Man Of His Word
"Dont confuse them with facts"

None dare so accuse MarkThe Great, who at 3:21 PM yesterday wrote:
"1) Even hard liquor contains less than 10% alchohol.
2) We don't drink millions of gallons of alchoholic beverages per day."

As a matter of fact --
1. 86 proof is 43% alchohol
2. If 21.2 of 300 million Americans have one 12 oz beer today ,that's 2 million gallons

Reference :

It's getting thicker at the top
"Recent growth in the interior regions of the Greenland Ice Sheet is reported by a Norwegian-led team of climate scientists. The growth is estimated to be about 6 cm per year during the study period, 1992–2003. "

Cause and effect
Where is the data showing mean sea levels are rising?

You asked for it, and it ain't in 'State of Fear'
the Topex satellite data are at

I see: you knw better than the NAS
The NAS, established by Abraham Lincoln, is the official scientific body whose mission it is to give the best possible scientific advice to the U.S. government. Its membership includes more than 200 Nobel prizes, and election as a member is regarded as one of the highest honors in science. If it takes a position, it will be one agreed to by the vast majority of scientists in the subject. And if you don't know this, it's because you don't want to know it.

>Some of us are old enough to remember that scientists can be quite wrong.

Scientists are wrong all the time, but science eventually gets it right, as it is doing in this case. Or maybe you just don't believe science. That's fine. I believe astrologers don't foresee a big problem with climate change.

How do you explain: the decreases near the poles, the increases near the equator and the 10mm/yr error in the Philippine Sea?

How does this correlate with estimated total ice cover changes?

Correlation does not mean causation.

Sound science?
"...What is clear, however, is that on this issue, science and policy have
become inextricably mixed to the point where it will be difficult, if not
impossible, to separate them out...."

If the science were sound, there would be no debate.

No Subject
They are best explained as examples of how geophysical illiteracy renders you incapable of reading the best data relative to the geoid presently available to science, and thus forces you to depend on the ludicrously one sided set of references poor Mike was prevailed upon to plug into his last, and fastest obsolescing , work of science fiction.

At least he's trying to catch up . What's your excuse ?

Just guessing...
"The word that got filtered above is s*p*i*c*e."

I'm just guessing, but it seems possible that the filter is meant to pick up phrases like, "spi*e up your l*ve life."

Hey, is that your thumb on the scale?
Dr. Michaels-- You would do well to admit that in a 2002 study, Rignot and Thomas double checked their conclusions by first calculating the amount of ice lost from calving at the margins of the shield against fresh accumulation from snowfall in the interior. Then they measured the actual decrease in thickness of the shield itself. Performing a mass budget analysis, they calculated a net annual loss of 50 cubic kilometers (12 cubic miles) per year. The latest study comments that net loss has accelerated since those measurements were taken.

To ostentatiously call attention to their finding that Greenland is accumulating ice at the rate of 5.4 cm per year, without also offering their figures on how much ice Greenland is losing, goes beyond obfuscation into the realm of a wilful misleading of your public.

The scientists involved in this research are not "speculating" that the ice is melting; they are measuring the rate of melt. I have no idea what axe you may be grinding by concocting this debate, but it lies in the realm of propaganda rather than science. Why not offer your readers the studies themselves, so they can judge from what is actually being stated as findings?

Here is the original study you cite from Hanna et al. It gives a rather different picture than the one you allege.

Play fair with the evidence, Doctor. Many scientists are at work measuring the mass balance of this chunk of ice, and their work is in close agreement. Melting is outpacing accumulation, and the rate of net loss is accelerating.

Good point
Good point-- I hadn't thought of it. The mass-balance method might be very good for establishing the total mass of the ice sheet, but it's less than definitive for projecting any resulting rise in sea level. Melting ice at the margins goes directly into the sea, while snow accumulation comes from atmospheric moisture-- and only indirectly from the sea.

To the degree that there is a measurable net warming in the atmosphere, there should also be an increased capacity to hold moisture. I wonder whether anyone is doing the calculations implied by this notion.

Finally, isostatic rebound could be excluded from the calculation by observing the differential between the rate of rebound in the rocks vs. the mean altitude at points on the shield surface. I haven't read the studies that closely. Can we assume they've adjusted for that?

A third party weighs in
Tlaloc-- I hate to butt into what looks like a private fight, but can't resist. Let me suggest your love of advocacy journalism has skewed the debate away from events on the actual scientific front.

First, there is no side anywhere that maintains "the science is settled". Science pretty much by definition is not settled. Anything can be over turned by new evidence or a new argument properly supported. However it can't be overturned merely by loud shouting. So don't cast your side as being the debunkers. Most of this alleged debunking is just playing with words.

I also tire very rapidly of people who spout blatant falsehoods. Por ejemplo, I know of no one who said we would be "running out of oil by 2000". This is what is known as a big fat lie. Por otro ejemplo, I know of no one who claimed there would be 20 billion people on earth by the year 2000. And you don't either.

Go back and peruse your Paul Ehrlich for supporting statements. I will happily eat some crow if you can support either claim. Let's stick with facts.

False premise
TML-- Contingency planning just doesn't work that way. You don't put all your eggs in one basket, banking on the notion that either (a) we're certain there will never be any problem or (b) all is lost-- we'll all die tomorrow. In fact this whole thing is unfolding between the two extremes.

There is no serious doubt but what both natural and man-made trends are contributing toward a sharp warming trend in today's-- not just tomorrow's-- climate.

There is no doubt but what our attempts to alleviate man's contribution to this trend will exacerbate the damage we have to endure from it. In other words, doing something about it can't hurt.

There is no doubt that there will be great costs as well as great opportunities resulting from the challenge of addressing the issue. Neither is there any doubt that ignoring the issue will entail even greater costs.

Also, there is a concurrency of interests in weaning ourselves from fossil fuel dependency. The supply is diminishing, and we'll need to find new sources of nonpolluting energy. At the same time the exhaust fumes are changing the character of the air itself. Feedback mechanisms we're looking at seem inclined to take the process further out of balance, not correct for it.

In any event momentum will dictate that the turnaround time for man's great Ship of Progress will not be instantaneous. That means that the time to begin moving the rudder is now. Unless you don't believe in the possibility of icebergs. IMHO

I would encourage you to look at the source you provided. In particular I looked at the global sea level change map and observed that sea level changes are not all positive and that the second map presented suggested significant errors in various locations.
Maybe the data is not presented correctly.
I think my degree in engineering physics helps me to understand the data.
Or, maybe you can explain it to me?

Piled further out, too
"Just wondering what happens as more ice builds on Greenland, would that apply more downward force adding a bit more push to the ice on the edges accelerating the ice flows into the sea?"

Sure would, marjon. But it wouldn't cause the ice to melt. Instead, an unbroken ice shelf would extend further and further out from the continent.

This isn't happening.

One thing you could look up on your search engine is the link between warming trends and increased precipitation. There is a direct connection, causing one to suspect increased warmth whenever you have more snow falling.

Look, for instance, at Antarctica. At that temp the air contains essentially no moisture whatever. The continent is dryer than the Sahara. Ergo, little or no precip. Also, ice tongues and shelves off the continent, rather than (until recently) melting and calving.

...and thinner at the edge
marjon-- You give the distinct impression that you think the researchers Michaels is attacking have all forgotten to look at increased precipitation atop the continent. Have you actually looked at anything they've written?

A little knowledge can be dangerous
I think you're missing the point, dp. No one is contesting that the earth has been warmer than it is today for much of its history-- nor do they doubt that life per se will flourish in carboniferous climate regimes.

What concerns us is that abrupt climate change of any sort imposes serious difficulties on civilization. We have decided to build our homes here, not in Siberia or northern Canada. You can take the long view if you like, and console yourself with the thought that "life" will adapt. But that's no consolation for the Iowa corn farmer who goes under from drought, while the corn belt moves to Saskatchewan.

This is just my observation, but your post displays a vast amount of seeming scholarship exclusively drawn from a Flat Earth point of view. You might want to expand your horizons a bit, and read beyond the parameters of the GW-is-a-hoax crowd.

Answer me this...
The question should not be are sea levels rising, but has the volume of water on the earth increased?
Sea levels are afected by sun, earth, moon system gravity, by the earths angular momentum, by subduction zones lifting continents, by rifts pushing continets apart, by erosion filling in bays, by undersea volcanoes and earthquakes, by gravitaional anonomolies, by...
Satellite data may be able to measure to a gnat's behind a nominal level.
The challenge is to explain the changes.

Non Sequitur
As usual, Eric argues a point that in not under consideration, and does it by an arguement to authority. I am not aware that the NAS has weighed in on the question of the impact of the NAO on hurricanes and Greenland melting. If so, enlighten me. Michaels is joined in his position by Grey and Landsea. And there is my arguement to authority.

Where's your thumb

Perhaps you strain at a gnat while swallowing the camel. I think that the Greenland ice balance record being discussed is an 11yr one. The various authors may well be correct that over this period there is a net loss and that year-over-year the size of the loss is increasing. To conclude anything about what will happen in the future is pure speculation. Some would claim that this is due to AGW, Michaels offer an alternative explanation in the well known NAO cycle. 11yrs is not enough to decide between them.

BTW, ice in Greenland does not melt because it is warming in Alaska. The warming needs to be in Greenland and would be the proper correlate.

The camel swallowed it
It's fair enough to call attention to our short baseline for measurements. But even if we only have eleven years of accurate work here, the fact that the order of magnitude is in cubic miles per year, and the acceleration rate is a sharp one, does give me some sense of urgency.

The issue is not, of course, whether future projections along or against this trend are beyond all doubt. As we both know, the future is brim full of doubt. The question, to me, is whether there is ANY significant cause for concern. And I think you know the answer to that.

I am recalled to the moment of the man who fell off the observation tower of the Empire State Building. While passing the 33rd floor he was heard to observe "Future trends don't look good, perhaps, but there is a bracing wind in the air and it's a fine day."

As for causation, I will agree that ice in Greenland may not be melting because it's warm in Alaska. But of course it's getting much warmer in both places-- and the Alaskan permafrost is doing something it hasn't done in a great many thousand years. Coincidence?

A quick answer
Every coastline on earth is either rising, falling or staying even, relative to the volume of water filling the basin. Calculating the net worldwide sea level is not an easy task. You have to construct many points of measurement, then take an average.

One of the factors causing a net increase in volume (while implying no increase in the total AMOUNT of water) is heating. Most measurements indicate the ocean growing warmer, when comparing apples to apples (location, depth and time of year). Warm water occupies more volume than cold. So that is one thing that's contributing to the net increase in mean sea level.

Isostatic Rebound is Not Good
Where it is happening, because as the seabed rises in Hudsons Bay the water displaced outflows and raises sea levels globally . How Much- /
it's a bear of a volume integral, and the undersea rebound rate data are still very scant . But hey- it's raising sea level and it's due to climate change. Been doing both for neigh 13,000 years so somebody
must have written an op-ed in cuneiform blaming it for The Flood. Thaty makes it fair game as building block for Pat's next exercise in tower of babel construction, and his Green opposite number's too.-

Small signal, bad signal to noise ratio, tiny data set- it's the beau ideal of a Climate Wars subject for thise working both sides of K Street.

Inflection correction
It's actually more complex in the greenland case tahn in Antarctica, because of the lenticular cross section of the sheet - the thick middle has already forced the land under[ some of] the middle bits concave , so the dottom ofthe ice there is downhill from sea level, and the sheet extrusion towards the coast has gravity going against it- it's enough to drive you to computer flow modeling .

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