Archive for the ‘antarctic’ Category

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A new round of Antarctic ice alarm

March 28, 2015

The alarm of a catastrophic meltdown of the Antarctic cycles up and down every year or two.  A journal article says the rate of melt is increasing, the popular press picks up on it and breathlessly warns about huge sea level rises sinking coastal cities around the world. We are told that x number of gigatonnes of ice per year are being dumped off the continent and wreaking their havoc on the world.   Then another study says “not so fast,” the mass losses aren’t that great after all.  Or, some crazy old skeptics ruin all the fun by recklessly bringing some logic to the discussion.

Today we have “Volume loss from Antarctic ice shelves is accelerating” (Paolo, et. al., Science, 2015).  The abstract warns us

“Overall, average ice-shelf volume change accelerated from negligible loss at 25 ± 64 km3 per year for 1994-2003 to rapid loss of 310 ± 74 km3 per year for 2003-2012.”

310 km3 per year (roughly the same as 310 gigatonnes per year) is pretty high compared to most other estimates. So you will probably see many references to this number because the bigger and scarier the more the press likes it.  But for the more sober minded, consider the following comparison of ice loss estimates from “Ice sheet mass balance and climate change” (Hanna, et. al., Nature, 2013)

Various estimates of ice mass change in the antarctic

Various estimates of ice mass change in the Antarctic

How does the recent Science paper compare?  If we place it on estimate plots from Hanna’s paper it would look like this..

Ice sheet mass balance and climate change - Hanna - Nature - 2013 v4

The Paolo Nature paper is an outlier.  But lets take them at their word.  They say that the Antarctic, on average, shed about 300 more Gigatonnes of ice per year during the 2003 to 2012 period than during the 1994 to 2003 period.  Where did all this ice go?  In to the oceans, of course.  That is why we have the great sea level rise scare.

So it follows that the sea level should have been rising faster during the 2003 to 2012 period than during the 1994 to 2003 year period.  How much faster?  Well, every gigatonne of water dumped into the oceans raises the sea level by about 2.78 microns. So 300 gigatonnes of extra water per year would raise the sea levels about an extra 840 microns a year, or about an extra 0.84 mm per year.  We are told that satellite data indicates that the global sea level is rising about 3 mm per year.  0.84 mm per year is a significant fraction of 3 mm per year, so such a rate increase should really stand out in the sea level rise data..

Well, here is some of that satellite sea level rise data…

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This discussion has been about ice that is moving from the land to the sea and raising the sea level.  But let’s take a quick moment to look at the sea ice that surrounds Antarctica.  While this ice does not contribute to changes in the sea level, it does say something about the conditions in that area.

seaice_anomaly_antarctic - Cryosphere Today 150328

Do you see a trend?  I see a trend.  And I know there are variety of “just-so stories” to explain away this trend, but I am unconvinced.

Conclusion

Between 1994 and 2003 the average sea level rise rate was 3.77 mm/yr, according to satellite data (University of Colorado).  If the Antarctic were depositing an average of about 300 more gigatonnes of water in the ocean per year in the following years (2003 to 2012), then the average sea level rise rage from 2003 to 2012 should have increased by about 0.84 m/yr, to 4.61 mm/yr.

Instead, the average sea level rise rate from 2003 to 2012 dropped to 2.66 mm/yr.

The claim of a huge rise in ice loss from the Antarctic over this period is quite implausible.

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Time to recognize approaching Southern Hemisphere disaster

December 26, 2013

I warned the world before, and they ignored me, but the evidence continues to mount. The Southern Hemisphere, and maybe the entire world, is headed for a frozen doom.

All day long polar orbiting satellites fly over the Antarctic and the surrounding ocean and measure the extent of the sea ice.  The amount of ice waxes and wanes with the seasons, ranging from about 2 to 16 million square kilometers between southern summer and winter.

Thirty years of this satellite data have made it possible to calculate the average ice extent for any given day of the year.  The deviation from this average is called the “anomaly.”  It is this anomaly data that reveals the impending drastic changes in the Southern Hemisphere.

Here is the anomaly data for the last three years from the University of Illinois’ Polar Research Group…

advance rate

The anomaly is increasing by half a million extra square kilometers every year!!! To put this in perspective, the Earth has a surface area of about 500 million square kilometers. Roughly speaking, an additional 1/1000th of the Earth’s surface is covered by ice each year. Consider that the Southern Hemisphere sea ice maxes out at about 16 million square kilometers each year, then 32 years of the current increase rate would double this amount.

By 2050, a mere 36 years from now, the ice encased Tierra Del Fuego on the southern tip of South America will replace Greenland as the most ironically named place on Earth.  By 2100 the dairy farms surrounding the town of Gore in the Southern Plains of the South Island of New Zealand will be a frozen mockery to the same-named purveyor of global warming alarmism.

Here is what is in store for the Southern Hemisphere…

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You can’t deny this.  This is science!  My conclusion is based on the proven analysis techniques of NASA climate scientist Jay Zwally.

Has the 21st century brought us to a tipping point?

All the best data indicates that a tipping point has already occurred.  Think about this: according to NOAA data (see here and here) 8 out of 10 years with greatest Southern Hemisphere sea ice extent have occurred since 2000!  Here they are in order…

  1. 9/14/13
  2. 9/24/12
  3. 9/24/06
  4. 9/24/09
  5. 9/29/05
  6. 9/28/00
  7. 9/8/04
  8. 9/29/07

We also now know that the all time low temperature for the Antarctic was reached in 2010.  Satellite data shows that on August 10th, 2010, the Antarctic temperature descended to 136 ºF (minus 93 ºC).  This shattered the previous record of minus 128.6 ºF (minus 89.2 ºC), set in 1983.

That is a drop in the minimum recorded temperature of 7.4 ºF in a mere 27 years.  If that continues, as indicated by Jay Zwally type analysis, then the low temperature by 2100 could be minus 159 ºF (minus 106 ºC)!!!

The effects are already being felt

It is now the warm season in the Southern Hemisphere.  Sea ice is making its seasonal retreat, yet the Russian cruise ship, Akademik Shokalskiy, is trapped in the sea ice with “52 tourists, scientists and explorers” and a crew of 22.  You would think the combined brains of all those scientists on board would have kept them out of the zone of freezing water.  While the ship’s brochure points out that “Views are excellent from the large, open decks and the Navigation Bridge'” maybe they couldn’t see the ice coming from the vantage point of the “Lounge and bar, open late afternoon and evening with a wide selection of wines and spirits” (an essential feature of all scientific research vessels).  Our prayers go out to the scientists and others on this harrowing adventure as ice breakers race to free them the frozen grip of the sea.  I hope the sauna stays warm and the booze holds out until they get there.

Why the great silence?

Where are the voices of leading scientists and environmentalists?  Why haven’t you seen anything about this impeding hemispheric disaster on the front pages of the news papers or on prime-time news reports?  A subsequent post will soon answer those questions and break this issue wide open.  

Stay tuned…

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The Thermohaline Circulation Only Stops for Extreme, Unrealistic Models

June 4, 2009

Return to Criticisms of Al Gore’s “An Inconvenient Truth”

Gore gives a cartoon description of the ocean circulation system when he explains what has become known as the thermohaline circulation, or the meridional overturning circulation.  In his simplistic scenario the surface ocean current that flows north in the Atlantic, bringing warmth to northern Europe will be halted by melting ice from Greenland, subsequently throwing Europe into an ice age. 

Here is Gore’s explanation in his own words from the Inconvenient Truth movie:

The Earth’s climate is like a big engine for redistributing heat from the equator to the poles.  And it does that by means of ocean currents and wind currents.  They tell us, the scientists do, that the Earth’s climate is an non-linear system – just a fancy way they have of saying that the changes are not all just gradual, some of them come suddenly, in big jumps… And so, all those wind and ocean currents that have formed since the last ice age and have been relatively stable – they’re all up in the air – they change. 

And one of the ones they’re most worried about, where they’ve spent a lot of time studying the problem is in the the North Atlantic where the gulf stream comes up and meets the cold winds coming off the Arctic over Greenland and that evaporates the heat out of the gulf stream and the steam is carried over to western Europe by the prevailing winds and the Earth’s rotation.  But isn’t it interesting that the whole ocean current system is all linked together in this loop, they call it the ocean conveyor.

vlcsnap-324533And the red are the warm surface currents, the Gulf Stream is the best known of them.  But the blue represent the cold currents running in the opposite direction…

vlcsnap-32114Up in the North Atlantic, after that heat is pulled out, what’s left behind is colder water, and saltier water, because the salt doesn’t go anywhere. And so, that makes it denser and heavier.  And so that cold heavy dense water sinks at the rate of 5 billion gallons per second.  And then that pulls that current back south.ani-21

At the end of the last ice age as the last glacier was receding from North America the ice melted and a giant pool of fresh water formed in North America, and the Great Lakes are the remnants of that huge lake.  An ice dam on the eastern border formed, and one day it broke, and all that fresh water came rushing out, ripping open the St. Lawrence there, and it diluted the salty dense cold water, made it fresher and lighter so it stopped sinking, and that pump shut off.

 vlcsnap-549956-smallAnd the heat transfer stopped.  And Europe went back into an ice age for another 900 to 1000 years.  And the change from conditions like we have here today to an ice age took place in perhaps as little as ten years time.  So that’s a sudden jump.  Now, of course, that’s not going to happen again because the glaciers of North America are not there… Is there any other big chunk of ice anywhere near there…?  Oh, yeah [Gore says ominously, as the image pans to ice covered Greenland] we’ll come back to that one…

Later in the movie Gore tells us that Greenland is rapidly melting.  The point being that it will provide a massive amount of fresh water that will stop the the thermohaline conveyor and  “would raise sea level almost 20 feet if it ‘went,'” Gore tells us.  He tells us about water seeping to the bottom of the ice sheets where it “lubricates where the ice meets the bedrock” causing the ice to slide toward the ocean.

Then he shows a series of pictures purporting to show the amount of melting in Greenland.  Gore says…

ani-31

“In 1992 they measured this amount of melting in Greenland … Ten years later this is what happened…And here’s the melting from 2005”

 

Hosing Experiments

But what if…?  What if there were a huge amount of low density fresh water dumped into the North Atlantic where the high density water is supposed to be sinking, just like the giant Canadian lake crashing through the barrier of ice the Gore told us about?  This possibility is explored with computer models known as  “hosing experiments.”  In a hosing experiment a model that simulates the ocean and atmosphere circulation patterns is modified to artificially dump huge amounts of extra fresh water, as if from a giant hose, into some location in the ocean.   It has been found that when enough fresh water is forced in, the circulation can be slowed, but rarely stopped

How much fresh water do the hosing experiments use to nearly stop the thermohaline circulation?  Typically (or here), they use one million cubic meters of fresh water per second, for 100 years!!!  (One million cubic meters per second has its own unit name: One Sverdrup or 1 Sv).  How does 1 Sv compare to, say, the rate of water flowing over Niagara Falls?

Niagara falls168,000 cubic  meters of water fall over Niagara Falls every minute.  That is about 2,800 cubic meters of water per second.  So one Sverdrup of water is the same as about 350 Niagara Falls!  (1,000,000 / 2,800  = 357).  So, roughly speaking, if 350 Niagara Falls were dumped into the oceans around Greenland continuously for 100 years, then we could expect to see a significant slow down of the thermohaline circulation.

River systems discharging into the Arctic Ocean.

River systems discharging into the Arctic Ocean.

How does one Sverdrup compare to the freshwater discharge of ALL the rivers emptying into the arctic ocean?  One Sverdrup of fresh water amounts to nearly 32,000 km3 of water per year  (1 Sv  x 106 m3 s-1/sv x (86,400 s/day) x (365 day/year) = 31,536 km3/year).  The total fresh water discharge from all rivers into the arctic is only about 4,300 km3 per year.  So, typical hosing experiments that nearly stop the overturning circulation add a water volume about 7 times the amount of water from all rivers discharing into the Arctic Ocean combined.

What about Greenland?

Hosing copyGore ominously implies that the amount of fresh water needed to turn off the overturning circulation is just waiting to pour off of  Greenland, due of course (drum roll), to CO2 induced anthropogenic global warming.   His pictures of Greenland, shown above, imply that about half of Greenland’s 2.8 million cubic kilometers of ice have melted in the 13 years between 1992 and 2005.  This is wildly misleading.  Only a miniscule fraction of the area shown in Gore’s Greenland images actually melts every year.   This is evidenced by mass balance studies, which show Greenland loses on the order of hundred cubic kilometers of ice every year,  which translates into a measly 0.003 Sverdrups.

100 km3 /year= 1011 m3/year

(1011 m3/year) / (365 days/year) / (86,400 seconds/day)
             = 3 x 103 m3/second
             = 0.003 Sv

Put another way, one Sverdrup of fresh water is 86.4 km3/day.  So the hosing experiments pouring in one Sverdrup put about as much fresh water into the ocean each day (86.4 km3) as Greenland provides in a year (100 km3).

But if Greenland actually started melting, by some extraordinary circumstance,  300 times faster, then it would yield 1 Sverdrup, or 1,000,000 cubic meters, of fresh water every second.  What would happen after 100 years of melting at that rate?  Well, that’s a trick question, because at a melting rate that gives 1 Sverdrup of freshwater Greenland would run out of ice in about 90 years.  This is because Greenland has only 2.85 million cubic kilometers of ice, and one Sverdrup of water is the same as about 31,500 cubic kilometers of water per year.  Ignoring the difference in density between ice and water, then 2.85 million cubic kilometers divided by 31,500 cubic kilometers per year gives 90 years.

Conclusion

You don’t hear as much about the threat of the collapse to the thermohaline circulation today as you did a few years ago.  This is because it has become recognized as being a very far fetched possibility, even by most alarmists who want to maintain a shred of dignity.  But I have a feeling we will not see this wildly exaggerated threat removed from new editions of Gore’s “An Inconvenient Truth” anytime soon.

Return to Criticisms of Al Gore’s “An Inconvenient Truth”

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Reply to John Mashey

May 27, 2009

I recently had an exchange of comments with some folks at Millard Filmore’s Bathtub concerning one of my previous posts about sea level rise near Boston.  The discussion seemed to really strike a nerve with alarmist nag John Mashey.  He scolded me with the following comment- you can almost see him wagging his finger:

Mashey’s comment

Mr Moriarity’s views on SLR at this time are simply not worth reading, for reasons I will explain.

NOAA collects the data, but the past is not the future. For very good scientific reasons, NOBODY serious about climate science does a simple linear projection of last century’s trendline into the next one, unlike Mr. Moriarty’s suggestion.

That would be about as silly as claiming solar PV [invented where I used to work] scientists should already be getting 100% efficiency.

Within ~30 minutes’ of Tom’s NRELare places thick with expert climate scientists, which makes him one of the lucky people who can easily go talk to experts:

NCAR
UC Boulder
USGS-Denver

I’m a AAASmember: I did a quick search of Science (An adequately prestigious journal) for “sea level rise”, and from the first hit page picked out a few recent SLR articles by Colorado authors, all of which I’d already read, along with the relevant IPCC TAR and AR4 chapters, etc, etc. (*I’m* no SLR expert, but I often talk to people who are. )

Mr. Moriarty has strong views on SLR, and surely is a AAAS member and has read these papers, all of whom think SLR will be a serious (acclerating) problem. He *could* write an article for Science showing them wrong, which would make him (properly) famous, given the mass of physics that would haveto be overturned to preserve a simple linear trend.

See How Much More Global Warming and Sea Level Rise?, 2005, 8 authors from NCAR.

See Paleoclimatic Evidence for Future Ice-Sheet Instability and Rapid Sea-Level Rise”, 2006, of whose 6 authors, 2 are at NCAR,1 at UC-Boulder, and 1 at USGS-Denver.

See Glaciers Dominate Eustatic Sea-Level Rise in the 21st Century”>,2007, of whose 8 authors, 5 are at UC Boulder.Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise, 2008, of whose 3 authors one is at UC-Boulder.

See “On the basis of calculations presented here, we suggest that an improved estimate of the range of SLR to 2100 including increased ice dynamics lies between 0.8 and 2.0 m.”

(That’s probably as good a single estimate as you get right now. People are trying to model melt dynamics for places that have been frozen through recorded human history, complexified by various nonlinear effects, tipping points, etc. Ice-sheet issues are *hard*.)

NCAR says Community Ice Sheet Model Will Aid Understanding of Sea Level Rise.

“Scientists think that this mechanism might trigger the rapid retreat of the West Antarctic Ice Sheet – which could raise sea level by a meter or more within a century or less.”

See Dan Cayan (SCRIPPS)talk @ SFBCDCconference a year ago. This was not news,but right in line with mainstream science.

Specifically, see p 18-19, noting that some of the models are from NCAR. I used to sell supercomputers to NCAR and talk to their scientists. They are quite competent.

NCAR and USGS (and some of UCBoulder) are Federally-funded to do good science for us all. If Mr. Moriarty denigrates *their* work, he might want to think about the fact that most of *his* career has been supported by *Federal* tax money.

That’s money from me and the companies I’ve worked for. My home state (CA) since 1983 is far and away the biggest *net* contributor to the Federal budget, and none of NCAR, NREL, Fermilab, or Argonne are here, but we helped pay for them. [And this is OK with me, since I like to think America is a *country*, not just a collection of independent states; all those labs have made good contributions.]

LOOKING AHEAD
NCAR has regular lectures. So does UC-BOulder’s NSIDC.

If Mr. Moriarty actually wants to learn about the science, he has *real* experts nearby to visit, often.

I’m done.

My reply

John thanks for the thoughtful comment.  I hope you have had a chance to wind down get off your high horse during the holiday weekend.

Congratulations on being a AAAS member.  So am I.  And so are 120,000 other people.  For those of you who are impressed by John’s membership in the AAAS, let me fill you in on the strict requirements for membership.  Send a check – then you are a member. 

Oh, by the way, thanks for inventing solar PV, I guess without you I wouldn’t have a job.

Let’s talk about the papers you cited: 

#1  How Much More Global Warming and Sea Level Rise?  Science 18 March 2005: Vol. 307. no. 5716, pp. 1769 – 1772. 

John, did you actually read this paper?  Meehl, et. al., consider three possible scenarios from the Special Report for Emissions Scenarios (SRES).  Specifically, scenarios B1, A1B, and A2.  They ran two models on each of these scenarios. Here is what they found for 21st century steric sea level rise:

Low range scenario B1, model PCM: 13 cm

Low range scenario B1, model CCSM3: 18 cm

Low range scenario A1B, model PCM: 18 cm

Low range scenario A1B, model CCSM3: 25 cm

Low range scenario A2, model PCM: 19 cm

Low range scenario A2, model CCSM3: 30 cm

Let me translate that:  Under their worst case scenario and their most sensitive model you get 30 cm (12 inches) by 2100  Wow – pretty scary.  Note that the map at  “Impacts of Sea Level Rise on the California Coast,” which I mentioned in my earlier comment to alleviate your fear of the west coast going under water, and in which you need to zoom way, way in to even find the affected areas, were based on a much greater 140 cm (56 inch) sea level rise by 2100.

So John, why did you cite this paper.  Let me guess: You read the abstract and saw the words “additional 320% sea level rise.”  But you didn’t actually read the article, did you? These numbers don’t exactly fit the alarmists’ (Gore and Hansen for example) picture of cities under water by the end of the century.

#2  Paleoclimatic Evidence for Future Ice-Sheet Instability and Rapid Sea-Level Rise , 24 March 2006: Vol. 311. no. 5768, pp. 1747 – 1750

This paper has a preposterous flaw.  It assumes a 1% yearly increase in atmospheric CO2 levels for the 21st century.  That sounds pretty innocuous – “What’s the problem with the assumption of a 1% increase?”, you might ask.  The problem is that the actual increase is about 0.5% per year.  Check this yourself here.  (By the way, John, that’s a NOAA website.  NOAAis one of those entities with labs in Boulder that you imply I have never heard of.)  This 0.5% trend has been fairly consistent for decades.  You can get the raw data from Mauna Loa, take the derivative, even take the second derivative, and see that 1% is preposterous. 

You might say “Big deal, 0.5% or 1%, what’s the difference.”  This is like a compound interest problem.  Take 1.005 to the 100th power (0.5% increase for 100 years) on one of your super computers, then take 1.01 to the 100th power (1% increase for 100 years).  The rest of you readers can simply try this on your desktop scientific calculator.  See the difference?  Pretty big, isn’t it?

Here is a paper that you seem to have overlooked in your comprehensive literature search: An overview of results from the Coupled Model Intercomparison Project, Covey, et. al., Global and Planetary Change, Vol 37, 2003. 

Covey et. al. write about the same 1% per year CO2 increase, but warned “The rate of radiative forcing increase implied by 1% per year increasing CO2 is nearly a factor of two greater than the actual anthropogenic forcing in recent decades, even if non-CO2 greenhouse gases are added in as part of an “equivalent CO2 forcing” and anthropogenic aerosols are ignored.”  They conclude that this 1% “ increasing-CO2 scenario cannot be considered as realistic for purposes of comparing predicted and observed climate changes during the past century.”

#3  Glaciers Dominate Eustatic Sea-Level Rise in the 21st Century, Meier, et. al., Science, 24 August, 2007, Vol 317, 1064-1067

Meier, et. al, calculated a 560 mm rise in sea level due to melting ice by 2100 based on an accelerating rate of global ice melting.   They managed to concluded that the amount of ice melting each year had been, on the average, 32 Gigatonnes (Gt) greater than the previous year from 1995 to 2005.  They simply extrapolated this yearly 32 Gt increase out to 2100.   A 32 Gt yearly increase in the amount of global ice that melts each year, over the 10 year period from 1995 to 2005, would mean 320 Gt more ice was melting in 2005 that in 1995.  That translates into a sea level rise rate in 2005 that must have been 0.9 mm greater than the sea level rise rate in 1995 (320 Gt/year x  2.7 microns/Gt  = 0.9 mm/year).

But we have very good sea level rise data that covers the period from 1995 to 2005.  And John, you will be delighted to know that this data is maintained by the University of Colorado, in Boulder.

sea level rise

Take a good look.  Note that the sea level rises a rate of 3.2 mm per year from 1995 to 2005 as indicated by the line fit and the notation in the bottom right corner.  It does not start out at 3.2 mm per year in 1995 and go to 4.1 mm per year (3.2 mm/year + 0.9 mm/year) by 2005.  The rise rate clearly does not increase by 0.9 mm per year over that period of time. 

What should have happened by 2009?  Well, according to Meier the global rate at which water was added to the oceans should have continued increasing by an additional 32 Gt/year and therefore there should be 448 Gt { (2009 – 1995) x 32 Gt/year = 448 Gt/year) } more water added to the oceans per year in 2009 than in 1995.  That translates into a rise rate that is 1.2 mm/year greater in 2005 than in 1995.  If the slope of the line fit in the above graph were actually 3.2 mm/year in 1995, then by Meier’s logic it should have been 4.4 mm/year by 2009.  However, the graph clearly shows that, if anything, the rise rate is less in 2009 than in 1995.

Please feel free to actually read the paper by Meier, et. al.  Please examine their source of data and their data reduction.  Here is a nice sample of how they determined that the amount of ice melting from glaciers and ice caps (as opposed to ice melting form the Greenland or Antarctic ice sheets) is increasing:

 Figure 1 from Meier

They took a scattered set of Meier’s own data, showing the melting rate of glaciers and ice caps, and fit it to a line.  It is traditional to give some numerical indication of the quality of a line fit.  In this case Meier chose not to provide such an indication.  So I digitized his data and did it for him: the r-squared value of this data is less than a dismal 0.1.  They found the slope of the line to be 11.9 Gt/year/year and thus concluded that for each year between 1995 and 2005 the glaciers and ice caps were losing 11.9 Gt more ice than the previous year.  Then they extrapolated that rate out another 95 years.  To extrapolate a function out 10 times the actual data’s domain is risky under any circumstances.  When the data is this scattered as this, it is just plain silly. 

They then undertook equally rigorous analysis of ice changes from the Greenland ice sheet, the West Antarctic ice sheet and the East Antarctic ice sheet, added the results together and came up with their 32 Gt/year/year acceleration rate.

#4.  Kinematic Constraints on Glacier Contributions to 21st-Century Sea-Level Rise, Pfeffer, et. al., Science, 5 September 2008, Vol. 321. no. 5894, pp. 1340 – 1343

To their credit, Pfeffer et. al., work in this paper to put an upper limit on the sea level rise by 2100.  This immediately separates them from the wildest alarmists like Al Gore and James Hansen.  Their conclusion is the maximum sea level rise by 2100 is 2 meters.  But they say in the abstract “More plausible but still accelerated conditions lead to total sea-level rise by 2100 of about 0.8 meter.”  This is still quite high and apparently caught your eye, right John?

But what must happen for this 0.8 meter sea level rise?  Pfeffer et. al., use the following logic:

“Rapid, dynamically unstable discharge of ice through calving is restricted to glaciers with beds based below sea level. We identified and calculated the aggregate cross-sectionalarea of Greenland’s marine- terminating outletglaciers by using surface and bed topography (16) and measured ice velocities (5) to identify all potential pathways for rapid discharge, including channels presently flowing rapidly as well as potentially unstable channels (Fig. 1 and table S1). Cross-sectionalareas (gates) for each outlet were calculated at the point of greatest lateral constriction by bedrock in the glacier’s marine-based reach. Ice stream widths in Antarctica can vary in time, but for Greenland outlet glaciers cross-sectional areas are constrained almost entirely by bedrock topography. Of the 290 km2 total aggregate gate cross-sectional area, we identified 170 km2 as the aggregate marine based gate area where drainage to the ocean is not blocked by near coastalsills standing above present day sea level. All dynamic discharge (Table 2) must pass through these gates by 2100 to meet2- to 5-m SLR targets. We considered four scenarios: velocities were calculated for both the “marine based” gate (170 km2) and the “total aggregate” gate (290 km2) given both projected SMB and 10× inflated SMB losses. We then considered whether those velocities are realistic.”

They note that “The present-day average velocity of all Greenland outlet glaciers is 0.56 km/year when weighted by drainage basin area or 1.23 km/year when weighted by gate cross-sectional area.”  For the large sea level rises that they consider, these velocities must increase.  If we just look at the case that requires the smallest velocity increase to reach 2 meters of sea level rise by 2100 (i.e. the case that most favors your argument), then Pfeffer reports that the velocity for the discharge gates must go up to at least 26.8 km/year.

And they don’t say that this velocity must be achieved after 100 years of a slow acceleration.  Rather, they say “These velocities must be achieved immediately on all outlets considered and held at that level until 2100. Delays in the onset of rapid motion increase the required velocity further”

As you can see, the 2 meter rise requires the glacier velocity at the discharge gates to increase by at least a factor of 22. Right Now. Today. And then remain at that extraordinary velocity until 2100, winter, spring, summer and fall.

Here are some statements from the paper concerning their own velocity calculations: “The scenario velocities far exceed the fastest motion exhibited by any Greenland outlet glacier.”  “A comparison of calculated (Table 2) and observed (1.23 km/year) average velocities shows that calculated values for a 2-m SLR [sea level rise] exceed observations by a factor of 22 when considering all gates and inflated SMB and by a factor of 40 for the marine gates without inflated SMB [surface mass balance], which we consider to be the more likely scenario.”  “Although no physicalproof is offered that the velocities given in Table 2 cannot be reached or maintained over century time scales, such behavior lies far beyond the range of observations and at the least should not be adopted as a central working hypothesis.”

By extension, the glaciers would have to increase velocity by a factor of 9, today, right now,  and continue at that rate until 2100 to achieve the 0.8 meters. 

What would cause the glaciers to increase their velocity to such an extent?  The going theory at the time the Pfeffer paper was written was that melting water would make its way to the bottom of the glaciers and lubricate their motion to the sea.  Even Al Gore talks about this in his famous “An Inconvenient Truth.”  But data subsequent to the Pfeffer paper have shown that not to be the case. “Large and Rapid Melt-Induced Velocity Changes in the Ablation Zone of the Greenland Ice Sheet,”  R. S. W. van de Wal, et al., Science 321, 111 (2008).

Van de Wal, et. al., note:

Here, we present ice velocity measurements from the major ablation area along the western of the ice sheet. The data set contains simultaneous measurements of ice velocity and ablation rates, which makes it possible to study the relation between ice velocity and meltwater input on longer (>5 years) and shorter (~1 day) time scales…

Annually averaged velocities are completely decorrelated to the annual mass balance, whereas a correlation might be expected if there is a strong feedback between velocities and melt rate, leading to enhanced flow, surface lowering, and increased melt rates…

In earlier work (4, 7), it has been suggested that the interaction between meltwater production and ice velocity provides a positive feedback, leading to a more rapid and stronger response of the ice sheet to climate warming than hitherto assumed. Our results are not quite in line with this view. We did not observe a correlation between annual ablation rate and annual ice velocities. Ice velocities respond fast to changes in ablation rate on a weekly time scale. However, on a longer time scale, the internal drainage system seems to adjust to the increased meltwater input in such a way that annual velocities remain fairly constant. In our view, the annual velocities in this part of the ice sheet respond slowly to changes in ice thickness and surface slope.

So, it looks like you will have to live with the disappointing news that the planet is not doomed by rapid sea level rise after all.  And your approval for grand plans to save places like Boston and San Francisco may not be needed.  Don’t lose hope though, with any luck the planet will be threatened by a giant meteor and the services of your brilliant mind will be needed after all.

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Polar bears listed as endangered, while global sea ice anomaly is above average

May 15, 2008

They finally did it.  Today the polar bear was listed as an endangered species.  The New York Times reports 

The Center for Biological Diversity, Greenpeace and the Natural Resources Defense Council filed suit in 2005 to force a listing of the polar bear. The center, based in Arizona, has been explicit about its hopes to use this — and the earlier listing of two species of coral threatened by warming seas — as a legal cudgel to attack proposed coal-fired power plants or other new sources of carbon dioxide emissions.

The thrust of the argument that echoes around the internet and appears over and over again in the popular press is the following sequence: 1. Anthropogenic CO2 causes the planet to heat. 2. This causes more summer ice melt. 3. The longer duration of open water in the summer and fall hampers the bear’s seal hunting and breeding. 4. Bear population diminishes.

There was, in fact, a fairly rapid decrease in Arctic sea ice extent sea ice extent over the last few years.  But the losses were almost entirely recovered in an unprecedented ice build-up of Arctic sea ice in the last months of  2007 and the first months of 2008

The alarmists base their argument on the studies of the bear’s habitat by the IUCN World Conservation Union.   Much has been made of the IUCN’s list of the “observed or predicted trend” for the nineteen sub-populations of polar bears. Most people are not aware that only five of these nineteen populations are listed as “declining.”  These sub-populations are the Southern Beaufort Sea population, Norwegian Bay population, Western Hudson population, Baffin Bay population, and Kane Basin population.

What is the condition of the sea ice for these five populations today? See for yourself in the following graphs of sea ice area.*

Figure 1.  The Beaufort Sea, home of the Southern Beaufort Sea sub-population of polar bears, has had an almost exactly average seasonally adjusted sea ice extent for the last six months.

Figure 2.  The Canadian Archipelago is the home of the Norwegian Bay sub-population of polar bears.  This region has had an average seasonally adjusted ice extent for the last six months.

Figure 3.  The Hudson Bay is the home of the Western Hudson population.  The Hudson Bay seasonally adjusted sea ice extent has hovered around average for the last six months.  Although it has been below average for brief periods in the last month, at the time this post is being written it is slightly above average.

Figure 4.  The Baffin Bay / Newfoundland region contains the Baffin Bay and Kane subpopulations.  For most of the last six months the sea ice extent has been greater than the seasonally adjusted average.

 As the NYT article mentioned above made perfectly clear, this has been a battle over the alarmist’s fear of global warming, not about polar bears per se.  Global warming, they worry, is going to yield an ice free Arctic, and the land bound ice in the Antarctic is on the verge of melting and flooding the coastal regions of the planet.  So, how does the overall global sea ice extent look, as of today?  While it has wiggled up an down about the average since satellites have been measuring it, and it stayed below average for several years, it is currently above average, as shown in figure 5, below.

Figure 5. Global sea ice area and anomaly.  Click on the image to enlarge the most recent anomaly data.  For the last several months the anomaly has been positive.  That is, the seasonally adjusted anomaly has been greater than the 1979 to 2000 average. 

My guess is that most of the alarmists are hoping and praying for a significant meltdown in the Arctic this summer.  Without such a meltdown it won’t be polar bears that are endangered, but their credibility.

*  Data for all figures from the University of Illinois Polar Research Group.  For figures 1 through 4 of the sea ice areas and averages were digitized from the U of I graphs of sea ice areas and anomalies using 48 increments per year.  Then the anomalies were subtracted from the sea ice area to give the 1979 to 2000 average.  Figure 5 is from the U of I web page, with additional annotation by ClimateSanity.

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The “Collapse” of the Wilkins ice shelf

April 1, 2008

A few quick calculations put the size and effect of latest broken piece of Wilkins ice into perspective

The recent “collapse” of the Wilkins ice shelf is causing quite a stir in the blogosphere.  The issue of disintegrating ice shelves is often entangled with the issue of sea level rise.  The Los Angeles Times carried an AP story on March 25th that reported:

…the western peninsula, which includes the Wilkins Ice Shelf, juts out into the ocean and is warming.  Scientists are most concerned about melting ice in this part of the continent triggering a rise in sea level.

The next day, CNN reported on the Wilkins ice shelf, saying:

…the poles will be the leading edge of what’s happening in the rest of the world as global warming continues.  Even though they seem far away, changes in the polar regions could have an impact on both hemispheres, with sea level rise and changes in climate patterns.

Although most reports do admit that this floating ice will not raise the sea level at all, they paint an ominous picture of land bound glaciers rapidly sliding into the sea.  In fact, the Wilkins ice shelf, like other ice shelves, is the product of a land glacier or ice sheet flowing over the coast and onto the water.

The piece of the ice shelf that broke off over the last month is reported to be 160 square miles (about 400 square kilometers).   It is “up to” 650 feet (200 meters) thick according to the Times Online.  A BBC video report corroborates the thickness by saying “Those cliffs are about 60 feet high,” when referring to the floating ice, which indicates that the total thickness is about 10 times that (because most of it is underwater), or about 600 feet (180 meters).  So, lets say the ice is about 0.2 kilometers thick (200 meters).  Then the total volume of the piece that broke off is about

400 km²  x  0.2 km  = 80 km³

One km³ of water will raise the sea level by a miniscule 2.78 microns (less than 3 millionths of a meter).  So, over the course of time that it took this 80 km³ volume of ice to move from the land to the sea it contributed to the sea level by:

80 km³  x  2.78 microns/km³  =  220 microns  =  0.22 millimeters  =  0.009 inches

That’s not very much, considering that it took many years. 

In general, it takes 360 km³ of water to raise the sea level by 1 mm.  In order for the Antarctic peninsula to contribute 12 inches (about 300 mm) to the sea level in 100 years, it would have to drop 1,080 km³ of ice into the ocean  (more really, because the density of the ice is less than the density of water) EVERY SINGLE YEAR FOR 100 YEARS!!  If the ice at the grounding line (where the ice leaves the land) were 0.33 km thick on average, then more than 3000 km² of ice would have to move into the ocean every single year.  Of course, this estimate is based on the unrealistic assumption that there would be no new ice accumulation on land from precipitation to offset the sea level rise.  The difference in the amount of ice sliding into the sea and the amount of ice building up on land due to snowfall is call the mass balance.

Typical estimates for the ice mass balance in the Antarctic Peninsula are nowhere near the 1,080 km³ (roughly 1,080 Gt).  The mass balance for the entire Antarctic continent doesn’t even come close.  Estimates for the entire continent vary greatly and have huge uncertainties.  Vilaconga and Wahr (2006) estimate a net ice loss of “152 ± 80 cubic kilometers of ice per year, which is equivalent to 0.4 ± 0.2 millimeters of global sea-level rise per year.”  Davis (2005) estimates a net increase in Antarctic ice, which would cause a net drop in sea levels.  Either way, the Antarctic is a very, very long way from any kind of catastrophic meltdown.

Then there is Greenland.  Luthcke (2006) estimates the mass balance for Greenland at a loss of 101 Gigatonnes per year.  This translates into a puny sea level rise of only 0.28 mm per year.

While we are at it, let’s consider James Hansen’s estimate of a 15 foot sea level rise this century. 

On the average, a 15 foot sea level rise in a hundred years translates into 46 millimeters per year, requiring 16,500 km³ of additional water per year!  This is about 65 times the current rate of ice melt, if we accept the mass balances of Vilaconga and Wahr for the Antarctic and Luthcke for Greenland.  If the ice sliding into the ocean is a third of a kilometer thick, then Hansen’s doomsday scenario would require 50,000 square kilometers of ice to move from land to ocean every single year!!!!

The bottom line

Pictures of huge chunks of ice and making scary comparisons like “Seven times the size of Manhattan” may get people excited, but they are not very enlightening.

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Davis, C., et. al., Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise, Science Vol. 308. no. 5730, pp. 1898 – 1901, 2005  Get copy here

Luthcke, et. al., Recent Greenland Ice Mass Loss by Drainage System from Satellite Gravity Observations, Science, Vol. 314. no. 5803, pp. 1286 – 1289, 2006   Get copy here

Velicogna, I. and Wahr, J., Measurements of Time-Variable Gravity Show Mass Loss in Antarctica, Science, Vol. 311. no. 5768, pp. 1754 – 1756, 2007  Get copy here