Posts Tagged ‘James Hansen’

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Computer simulations said “Yes,” Reality said “No”

April 6, 2013

Energy is the lifeblood of civilization – the more the better. One of the great hopes for the last 50 years has been clean energy from fusion, and many very fine physicists have dedicated careers to this holy grail.  Perhaps the greatest hope for fusion has been the National Ignition Facility at the Lawrence Livermore National Laboratory.

At the National Ignition Facility the plan is to compress a small bead containing hydrogen to the extreme temperature and pressure at which fusion will occur.  This compression would be accomplished with an extraordinary array of high-powered lasers that would all converge on to a tiny 2mm bead.  If all works well the enormous amount of energy to power the lasers would be more than replaced by the energy released by the fusion reaction.  The hope is to repeat this process with a new hydrogen bead 16 times a second, yielding a continuous supply of useful heat to generate electricity.

Scientist at the National Ignition Facilty expected that hydrogen ignition (the point where fusion occurs and more energy is released than invested) would occur last year.  But it didn’t.  According to ScienceNews

A lot of that confidence came from computer simulations… Each simulation consisted of more than a million lines of code filled with numbers and equations describing every push and pull that nuclei in the fuel capsule would encounter once the laser fired. All the data included in the simulations were based on well-tested theories and rigorous experiments, including measurements from hundreds of thermonuclear bomb explosions. The world’s fastest supercomputers required days or weeks to spit out the results.

Many of these simulations predicted that NIF’s 192-beam laser would comfortably achieve ignition. They showed that a short, powerful laser pulse coming from all directions would compress the pellet enough to create heat and pressure more intense than that in the sun’s core, forcing hydrogen nuclei together to form high-energy helium nuclei and neutrons.

No such luck.

Ignition was a failure.  I am not condemning the scientists at the National Ignition facility.  In this type of endeavour failure is just a stepping stone to success.  In fact, I  have great admiration for the folks working on this project and I hope funding and research continues.

Complex simulations

Here’s the thing: those millions of lines of code were modeling something that is relatively simple.  Hydrogen nucleosynthesis is well understood.   The models had to simulate just a single compression and ignition event. There were only a few variables compared to the thousands of variables for something as complex as, say, the climate of the planet Earth.

I have a lot more faith in talents and mental horsepower of the quiet anonymous physicists modeling the relatively simple fusion of hydrogen than I have in some of the self-important bumbling climate modelers working on the vastly more complex climate of the planet.

Just consider the grand poobah of climate modelers, James Hansen.  Ira Glickstein did a nice job of pulling back the curtain on Hansen’s modeling skills with this …

James Hansen’s 1988 models vs reality, From Ira Glickstein, WUWT, 3/20/2013)

The folks at the National Ignition Facility run their experiments, perhaps sometimes chastened by the results, but wiser and closer to their ultimate goal.

Hansen’s experiments are run by nature and take decades, but when he is wrong he is hardly chastened.  Hansen retired from his position at NASA a few days ago.  The Washington Post reported that Hansen said he was retiring so he could “spend full time on science.”  Does that mean he wasn’t spending his time on science at NASA?  His friend, Bill McKibben was probably closer to the mark when he said Hansen “decided to step down so he could engage in lawsuits and protests full time.”

Hansen was also predictably lauded by his friend Gavin Schmidt.  I guess McKibben and Schmidt haven’t seen the above graph.

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Its even worse than Al Gore said

February 8, 2013

I was amused to read the meme about global warming being like the explosion of 400,000 Hiroshima atomic bombs every day on the planet.  Both James Hansen and Al Gore have made this claim.

Guess what? They could be right!

And here is another thing: The CFL bulbs in my basement are like the detonation of a pound of TNT every day!

First, the 400,000 Hiroshima atomic bombs meme

Presumed extra CO2 forcing: This value is highly debatable, but I will play along with a commonly quoted warmist value: 0.6 Watts/m2 = 0.6 Joules /( s  m2 )
Surface area of the Earth: 5.1 x 1014 m2
Seconds in a day: 86,400 s / day
Yield of Hiroshima bomb: 15 kilotons of TNT
Kilotons of TNT to Joule conversion: 4.2 x 1012 Joules / kilotons of TNT

So, presumed total forcing due to CO2:
{0.6 Joules /( s  m2 )} x {5.1 x 1014 m2} x 86,400 s / day
≈ 2.6 x 1019 Joules / day

The yield of Hiroshima bomb in Joules:
{15 kilotons of TNT} x {4.2 x 1012 Joules / kilotons of TNT} = 6.3 x 1013 Joules

Number of Hiroshima bomb equivalents per day:
{2.6 x 1019 Joules / day} / {6.3 x 1013 Joules} ≈ 400,000 / day

Detonation of TNT in my basement

Number of CFLs in main basement room: 6
Power of each CFL: 16 Watts = 16 Joules / second
Operating time each day: 6 hours = 21,600 seconds

energy released by the CFLs in my basement:
6 x {16 Joules / second) x {21,600 seconds} ≈ 2.1 x 106 Joules

Equivalent mass of TNT:
{2.1 x 106 Joules} / {4.2 x 1012 Joules / kilotons of TNT} = 5 x 10-5 kilotons of TNT
=  0.5 kilograms of TNT ≈ 1 pound of TNT

But it gets even worse

As if it weren’t bad enough having the equivalent of a pound of TNT blowing up in my basement every day – there is something worse. Much worse.

The sun irradiates the surface of the planet with enough energy for my own personal Hiroshima atomic bomb blast every 40 days or so.  And your own personal blast. And a blast for every single man, woman and child.  The equivalent of 7 billion Hiroshima blasts every 42 days!

Average insolation at the surface of the Earth: 250 W/ m2 = 250 J / s /m2
Surface area of the Earth: 5.1 x 1014 m2

Total solar power at the surface of the Earth:
{250 J / s /m2} x {5.1 x 1014 m2} ≈ 1.25 x 1017 J / s

So how long does it take for the equivalent of 7 billion Hiroshimas?

Energy of 7 billion Hiroshimas / total solar power at the surface of the Earth
= {7 x 109} x {6.3 x 1013 Joules} / {1.25 x 1017 J / s} ≈ 3.6 x 106 s ≈  42 days

So there you have it, we all get our own personal Hiroshima every 42 days.

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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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Boston Underwater?

March 24, 2009

Boston, you have been warned. Sea levels are rising , and if one of the IPCC’s five scenarios is correct, the world’s oceans will rise somewhere between 18 and 59 cm (7 to 23 inches) by 2100. If that isn’t terrifying enough for the people living on the New England coast, the Boston Globe now tells us that the ocean near Boston will rise 8 inches more than the world average. How will the hapless rubes of Boston cope with this onslaught of Atlantic water?

I wouldn’t lose to much sleep worrying about the folks in Boston when it comes to pushing back against the ocean. Excerpts from the following maps were used to make an animation of the changing coastline in Boston:

  • A 1775 map showing the Boston area with the rebel military works. Note especially the isthmus, known as Boston Neck< that connects the town of Boston to the mainland.
  • An 1838 George W. Boynton engraving of Boston area from a Thomas G. Bradford atlas.
  • USGS map of Boston area.
  • A 2009 satellite image from Google Earth

The top of the animation shows the maps after photoshopping to make the land and water more obvious. The bottom of the animation shows the unaltered excerpts of the maps or images.

animation-5I

The panic prone will argue that our Bostonian ancestors dealt with a static ocean, not a rising ocean. Not so fast. Check out the NOAA graph below (click inside graph to see it in context at NOAA site). It shows a sea level rise rate of 2.63 mm/yr for the last 100 years in Boston. At that rate it will rise 23.9 cm (9.4 inches) by 2100.

Boston sea level rise

Boston sea level rise data from NOAA. Click in image fro view in context.

Anyone who panics over the IPCCs 100 year projections of rising sea levels does not understand the perseverance and ingenuity of free people. Then there are others, like James Hansen, who enjoy the feeling of panic so much that that they exagerate the probable sea level rise for this century to get their thrills. But that is a story for another day…

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An easy climate change / energy quiz

November 13, 2008

Here is a simple, fun, 10 question quiz that covers a sample of climate change and/or energy issues.   Simply check the appropriate box and push the “vote” button for each question.  After you have pushed the vote button you will see the accumulated wisdom of everybody who has answered that question so far.  You can even leave a comment for any question, which I encourage.

Note that several of the questions requiring numerical answers have “order of magnitude” choices.   That is, they require “back of the envelope” type approximations, not high precision.

At the bottom of the quiz you will find a link to a solutions page, with links to supporting evidence, and “back of the envelope” calculations.  If you want, you can look at the solutions first and then take the quiz – but that would be cheating!

After enough people have answered the questions I will post the results at ClimateSanity.

Have fun!

 QUESTION 1. 

 Here are five false color images of the sea ice in the arctic.  The images represent the ice on five year intervals on July 18th of 1988, 1993, 1998, 2003, and 2008.  Your task is to use your knowledge of changing conditions in the Arctic to put them in the proper chronological order.  Note that each image uses the same color scale (shown in the upper left corner of each image) to indicate the density of ice as a function of position. 

Image 1

Image 2

Image 3

Image 4

Image 5

 

Question 2

 

Question 3

In the fall of 2007, after the northern summer melt season, the Arctic sea ice extent anomaly reached its lowest level since satellite monitoring began in 1979.  This was followed by warnings that the Arctic ice could be completely gone by the summer of 2012. 

 

Question 4

In 1979 the worst nuclear accident in US history happened at Three Mile Island nuclear power plant near Middletown, Pennsylvania. 

 

Question 5

A rising sea level is one of the feared symptoms of global warming.  According to the Jason and Topax satellite tracking of ocean levels, the average sea level rise rate for the last 10 years has been about 3.2 mm per year.  This is interpreted by some to indicate an accelerating sea level rise rate.  IPCC expert Simon Holgate’s 2004 data (Holgate, S.J., and P.L. Woodworth, 2004: Evidence for enhanced coastal sea level rise during the 1990s. Geophys. Res. Lett., 31, L07305, doi:10.1029/2004GL019626.) was prominently featured in the IPCC’s Fourth Assessment Report (AR4, Working Group 1: The Physical Science Basis of Climate change, Chapter 5).  In a more recent 2007 paper (S.J. Holgate, “On decadal rates of sea level change during the twentieth century“, Geophysical Research Letters34: GL019626 (2007)., Holgate reconstructed sea level rise rates from high quality tidal gauge data going back to about 1900.

 

Question 6

NASA Scientist James Hansen estimated a sea level rise of 15 feet for the 21st century.

 

Question 7

The northern coast of Greenland is at 83.5 degrees north latitude.  It is the closest land to the North Pole.  Satellite data since 1979 has always shown this region locked in sea ice.  If global warming were to result in an ice free arctic sometime during this century, it is believed that this area would be the last place to lose its summer ice.

 

Question 8

Compact fluorescent light bulbs use only 25% of the energy of an incandescent light bulb to give the same number of lumens of light.

 

Question 9

 

Question 10

Since 1963 Africa’s Lake Chad has experienced severe shrinkage.  While atmospheric CO2 levels have continuously increased since 1963, the surface area of the lake has dropped from about 25,000 square kilometers to about 1,500 square kilometers.  This fact has been presented by Al Gore and others as a consequence of anthropogenically induced global warming.  Of course, this evidence must be considered in comparison to how the lake was changing when CO2 levels were not increasing. 

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***Click here for quiz solutions***

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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

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