Archive for the ‘glaciers’ Category

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Rahmstorf: Is it OK to call him an “alarmist” now?

May 9, 2012

Some folks never give up.  In the following video Stefan Rahmstorf says…

To me a tipping point in the climate system is like a sweet spot in the climate system, where a small perturbation can have a major, even qualitative effect.  It’s like a small change in temperature moving, for example, the Greenland Ice sheet beyond the point where eventually it will melt down all together…from about 2 degrees global warming there would be a risk of the complete meltdown of the Greenland Ice sheet…I think this two degree limit agreed in Cancun by the politicians may not be enough to prevent a dangerous interference in the climate system.

Now let’s be clear about this: a “complete meltdown” of the Greenland ice sheet would raise the planet’s sea level 7 meters (7000 mm).  The sea level rise rate today is about 3 mm per year and decreasing according to satellite data.  A rational reading the tide gauge data is even less.

I guess in Greenland ice must melt at -25°C.  Here is today’s temperature outlook…

Oh, I know, the scientifically sophomoric sophisticated will tell us all about the rapidly accelerating glaciers.  Well, their favorite journal, Science, throws a little icy cold water on their dreams of catastrophic nirvana.  In 21st-Century Evolution of Greenland Outlet Glacier Velocities ( T. Moon, et. al., Science, 4 May 2012, Vol. 336, pp. 576-578)  Moon et. al. produced “a decade-long (2000 to 2010) record documenting the ongoing velocity evolution of nearly all (200+) of Greenland’s major outlet glaciers.”  They found that in some regions there was a glacier acceleration (SEE! SEE!), but not very consistently over the last 10 years.  Here is their conclusion

Our observations have implications for recent work on sea level rise. Earlier research (33) used a kinematic approach to estimate upper bounds of 0.8 to 2.0 m for 21st-century sea level rise. In Greenland, this work assumed ice-sheet–wide doubling of glacier speeds (low-end scenario) or an order of magnitude increase in speeds (high-end scenario) from 2000 to 2010. Our wide sampling of actual 2000 to 2010 changes shows that glacier acceleration across the ice sheet remains far below these estimates, suggesting that sea level rise associated with Greenland glacier dynamics remains well below the low-end scenario (9.3 cm by 2100) at present. Continued acceleration, however,may cause sea level rise to approach the low-end limit by this century’s end. Our sampling of a large population of glaciers, many of which have sustained considerable thinning and retreat, suggests little potential for the type of widespread extreme (i.e., order of magnitude) acceleration represented in the high-end scenario (46.7 cm by 2100). Our result is consistent with findings from recent numerical flow models (34).

So, Rahmstorf is worried about a “complete meltdown of the Greenland ice sheet” which would lead to 7 meters (7000 mm) of sea level rise, but the data shows “sea level rise associated with Greenland glacier dynamics remains well below the low-end scenario (9.3 cm by 2100)” (93 mm by 2100).  Does being off by a factor of 75 (7000/93) qualify as “alarmist?”

By the way, when Moon says “Earlier research (33) used a kinematic approach to estimate upper bounds of 0.8 to 2.0 m for 21st-century sea level rise” he is talking about 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).  I discussed this paper at length two years ago in my “Reply to John Mashey.” (Still feeling smug, John?) 

And finally,  Moon’s last sentence says “Our result is consistent with findings from recent numerical flow models (34).”  He is talking about Committed sea-level rise for the next century from Greenland ice sheet dynamics during the past decade (Price, et. al., PNAS, 31 May 2011, vol. 108 no. 22 pp. 8978-8983).    Price, et. al. say

The modeling conducted here and some reasonable assumptions can be used to make approximate upper-bound estimates for future SLR from GIS [Greenland Ice Sheet] dynamics, without accounting for future dynamical changes explicitly. As discussed above, numerous observations indicate that the trigger for the majority of dynamic thinning in Greenland during the last decade was episodic in nature, as the result of incursions of relatively warm ocean waters. By assuming that similar perturbations occur at regular intervals over the next century and that the ice sheet responds in a similar manner, we can repeatedly combine (sum) the cumulative SLR [sea level rise] curve from Fig. 4B to arrive at additional estimates for SLR by 2100. For example, if perturbations like those during the last decade recur every 50, 20, or 10 y during the next 100 y, we estimate a cumulative SLR from GIS dynamics by 2100 of approximately 10, 25, and 45 mm, respectively…Addition of the estimated 40 mm of SLR from changes in SMB [surface mass balance] by 2100 would result in a total SLR from Greenland of 85 mm by 2100.

Holy cow! Rahmstorf is telling us to be worried about 7000 mm of sea level rise due to the “complete meltdown of the Greenland ice sheet,” but Price et. al. say maybe 85 mm due to Greenland by 2100.

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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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Don’t Panic – The Arctic has survived warmer temperatures in the past

October 15, 2008

Since we are in the season of comparing charts, graphs and interpretations of the summer Arctic ice melt, it may be useful to pause and consider the history of Arctic temperatures in the Holocene.  There is an abundance of data compiled by hardworking field researchers over the years.  Before everybody got so excited about global warming, it was understood that the Arctic was considerably warmer in earlier parts of the Holocene than in the present.  The evidence for these warmer periods seems to have been forgotten in an age when satellite data causes us to fixate on the last thirty years.

I have collected a short list of papers that indicate times during the mid-Holocene, and places in or near the Arctic, when it was warmer than the present.  Some of these papers may also indicate warmer periods in the early or late Holocene, but I am concentrating primarily on the mid-Holocene in this post.  Figure 1, below, shows the spatial distribution of areas covered by these papers.  Click on the image to get a larger view.  Figure 2 shows the times in the mid-Holocene that each paper says it was warmer than the present.

Figure 1.  Numbers correspond to the journal articles that are listed below.  They also correspond to the numbered lines in figure 2.

 

 Figure 2.  “Paper #” corresponds to the numbered journal articles listed below.  The colored areas indicate the time periods in the mid-Holocene for which the papers indicate it was warmer than present.

 

The evidence that the Arctic was warmer in the mid-Holocene than it is now is compelling.  At longitudes almost completely encircling the Arctic, palaeological proxies of all kinds speak from the past with the same message.  Treelines moved in latitudes and elevations.  Alkenone molecules produced from sun loving organisms in the top layer of ocean water recorded the temperature of the water and settled into the depths of the ocean, depositing their temperature record in the sediments.  The pollens of various species of plants changed their ratios with changing temperatures and forest locations, drifted over lakes and settled to the bottom, leaving layer upon layer of temperature history.  Choronomid midges, small insects that live out their short lives in just a few weeks, varied their physiology according to the temperature of their environment, and carried their temperature stories to lake sediments. Forest plant species came and went at temperatures rose and fell, leaving behind their seeds in successive layers of soil as positive reminders that they had been there.

These proxies, and others, strongly indicate that the arctic region was warmer around 5,000 years ago than it is today.  Read the papers listed below to see the details.

Please feel free to criticize my interpretations of the papers, or to point out contradictory or complementary papers.

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1. Jung-Hyun Kim, Norel Rimbu, Stephan J. Lorenzb, Gerrit Lohmanna, Seung-IlNam, Stefan Schoutene, Carsten Ruhlemannf, Ralph R. Schneiderg, North Pacific and North Atlantic sea-surface temperature variability during the Holocene, Quaternary Science Reviews, 23, 2004

Kim, et. al., used alkenone-derived sea-surface temperature records from sediments from over 30 locations to derive temperature changes in the Pacific and the Atlantic Oceans during the Holocene.  I have marked the locations of the five highest northern latitude cores, two above the arctic circle and three below it.  Kim’s data for these cores covers only the last 7,000 years, rather than the entire Holocene.  Nevertheless, the cores show temperatures clearly dropping to modern values over the last 7,000 years.  The northern-most core (75N) shows a temperature drop of 4.4 degrees C since 7,000 years ago.  Two other cores show temperature drops greater than 3 degrees C (3.3 and 3.8 degree drops at 57.8N, 8.7E and 57.7N, 7.1E respectively).  The remaining two cores show temperature drops of 1.8 and 0.6 degrees C.  Get copy here.

2. Kultti, S., et. al., Past changes in the Scots pine forest line and climate in Finnish Lapland: a study based on megafossils, lake sediments, and GIS-based vegetation and climate data,” The Holocene, Vol 16 No3, 2004b.

In this paper, Kultti, et. al., (2004b) looked at tree lines in Finnish Lapland and found “Results indicate that pine reached its maximum distribution between 8300 and 4000 cal. yr BP. The inferred minimum shift in mean July temperature was at that time c. +2.5.” Get copy here.

3. Solovieva, N., and Jones, V., A multiproxy record of Holocene environmental changes in the central Kola Peninsula, northwest Russia, Journal of Quaternary Science, 17(4), 2002. 

Solovieva and Jones studied a multi-proxy record of the Kola Peninsula in northern Russia and concluded that for the period from 8000 years ago to 5400 years ago “A maximum of forest cover and the high Pinus abundance during this period indicate the Holocene climate optimum. The multiproxy data from Chuna Lake generally agree with the temperature reconstructions based on the evidence from the Greenland ice-cores (Stuiver et al., 1995) and summer temperatures were likely to have been 2°–3 °C higher than at present.” Get copy here.

4. MacDonald, G., et. al., Radiocarbon dated Pinus sylvestris L. wood from beyond tree-line on the Kola Peninsula, Russia, The Holocene, Vol. 10, No.1, 2000.

MacDonald, et. al., dated Scots Pine wood (Pinus sylvestris L.) in Russia’s Kola Peninsula and found “the density of trees north of the modern tree-line was greatest between 7000 and 5000 BP.  Get copy here.

5. Sarnthein, et. al., Centennial-to-millennial-scale periodicities of Holocene climate and sediment injections off the western Barents shelf, 75°N, Boreas, Vol. 32, 2003.

Sarnthein, et. al., studied sediments on the Barents shelf and found “disappearing sea ice from 6.4–5.2” thousand years before the present, and again “3.0–1.6 kyr BP.” Get copy here.
 

6. Kultti, S., Oksanen, P., and Väliranta, M., Holocene tree line, permafrost, and climate dynamics in the Nenets Region, East European Arctic, Canadian Journal of Earth Science, Vol 41, 2004a.

 “Pollen, stomata, and macrofossils in a lake core with a basal date of 9700 14C BPwere used to reconstruct past changes in climate and vegetation in the arctic tree line area, northeast European Russia” … “We interpret summer temperatures to have been ca. 3–4 °C higher between ca. 8900 and 5500 BP than at present, and the lowest temperature regime of the Holocene to have occurred between 2700 and 2100 BP.”
 

7. V.L. Koshkarova and A.D. Koshkarov, RegionalSignatures of Changing Landscape and Climate of Northern Central Siberia in the Holocene, Russian geology and geophysics, N 6, v. 45, 2004

 Koshkarova and Koshkarov(2004) draw their conclusions based on “25 sections of Holocene deposits and soils of northern Central Siberia [that] were studied by paleocarpologicalmethods. Special attention was given to the reconstruction of the dynamics of speciation of forest cover in time and space.” These 25 sections are all above the arctic circle and range in longitude from 86 to 119°E. They divide the Holocene in the region into “intervals 9-8 ka (thermal maximum), 6.5-5ka (climate optimum – combination of higher temperatures and higher humidity), and 2.5-2 ka (thermal minimum).  Get copy here.
 

8. Robert A. Monserud, Nadja M. Tchebakova, and Olga V. Denissenko, Reconstuction of the mid-Holocene Palaeoclimate of Siberia using a bioclimatic vegetation model, Palaeogeography, Palaeoclimatology, Palaeoecology, 139, 1998

 Monserud, et. al., concentrated on the mid-holocene, which they defined as 4600 to 6000 years before the present. They found that during this period the Siberian winters “between 60 and 65N the palaeoclimate was 5.3 C warmer on average, and between 65 and 70N it was 7.7 C warmer.” For the warmer months the found “Summer was 2-5 C warmer than today between 63 and 73N, embracing much of the Northern Taiga, Forest-Tundra, and Tundra zones. A band of moderate summer temperature anomalies (0 – 2 C) is centered at 65N, and a second band of greater anomalies (2-5 C) is centered at 70N.” Get copy here.
 

9. Ilyashuk, E.A., Ilyashuk, B.P., Andreev, A.A.b, Bennett, K.D., Hammarlund, D., Hubberten, H.W., Chironomid-inferred Holocene mean July air temperatures for the Lena River Delta area, East Siberia, and the Kola Peninsula, northwestern Russia, ACSYS Final Science Conference,11-14 November 2003, Arctic and Antarctic Research Institute (AARI), St. Petersburg, Russia

 Ilyashuk, et. al. show that Radiocarbon-dated chironomid records from the lake Nikolay region of the Lena River Delta area “imply the warmest (up to 2-3°C warmer than nowadays) climate during ca. 10,200-9200 cal. yr BP…with two short warm oscillations (up to 8.9oC) at c. 5600 and 4500-4100 cal. yr BP…and a relatively long warm period ca. 2300-1400 cal. yr BP.” Get copy here.
 

10. Matul, A. G., et. al., Recent and Late Holocene Environments on the Southeastern Shelf of the Laptev Sea As Inferred from Microfossil Data, Oceanology, Vol. 47, No. 1, 2007.

Matul, et. al., (2007) from the Russian Academy of Science studied microfossils from the Laptev Sea, which is north of Siberia and well within the Arctic circle. They found that “Judging from the increased diversity and abundance of the benthic foraminifers, the appearance of moderately thermophilic diatom species, and the presence of forest tundra (instead of tundra) pollen, the Medieval warming exceeded the recent “industrial” one and is reflected in the near-delta sediments.” But they indicate that it was warmer even earlier by saying “..the warming in the Laptev Sea during the period of ~5100–6200 years B.P. corresponding to the Holocene climatic optimum could be even more significant as compared with the Medieval Warm Period.”
 

11. Lawson, D.E.,et. al., 2007, Early to mid-Holocene glacier fluctuations in Glacier Bay, Alaska, in Piatt, J.F., and Gende, S.M., eds., Proceedings of the Fourth Glacier Bay Science Symposium, October 26–28, 2004: U.S. Geological Survey Scientific Investigations Report 2007-5047, p. 54-55.

Lawson looked at glacial advances and retreats in Glacier Bay, Alaska. Glacier Bay is well south of the Arctic circle, but yields information about northern latitude climates. They found a glacial retreat starting 6800 years ago followed by a new glacial advance starting 5000 years ago. The retreat “was long enough to develop a mature forest” on land that was subsequently recovered with ice. Get cop here.
 

12. Kaufman, D. S., et. al., Holocene thermal maximum in the western Arctic (0-180°W), Quaternary Science Reviews, 23, 2004

In a very comprehensive study of the western Arctic Kaufman and coauthors from the US, UK, Canada, Norway, Iceland, and Russia (2004), studied proxies from over 140 sites in the western hemisphere part of the arctic. Their abstract notes “Paleoclimateinferences based on a wide variety of proxy indicators provide clear evidence for warmer-than-present conditions at 120 of these sites. At the 16 terrestrialsites where quantitative estimates have been obtained, local HTM[Holocene Thermal Maximum] temperatures (primarily summer estimates) were on average 1.6 ± 0.8 ° C higher than present…”
They devided the region into four zones, which I have labeled on the map.
12a. Central Eastern Beringia.Sketchy evidence indicates that the Holocene Therma Maximum occurred very early and had a short duration in this region. Temperatures were several degrees above current temperatures for some period between 12.8 and 7.1 ka. (mean initiation plus one sigma to mean termination minus one sigma).
12b. Northern Continental Canada.Better evidence indicates that this zone experienced higher temperatures from about 7.3 to 4.3 ka.
12c. Canadian Arctic Islands.Good abundant data that this zone was warm from 8.6 to 4.9 ka.
12d. Greenland, Iceland and other Artic islands.Temperatures were high in this zone from 8.6 to 5.2 ka.
 

13. Stewart, T. and England, J., Holocene Sea-Ice Variations and Paleoenvironmental Change, Northernmost Ellesmere Island, NWT., Canada, Arctic and Alpine Research, Vol 15, No. 1, 1983.

 Stewart and England examined more than 70 samples or Holocene driftwood on Ellesmere at 82° N Latitude. The time distribution of the driftwood indicates “prolonged climatic amelioration at the highest terrestrial latitudes of the northern hemisphere” from 4200 to 6000 years before the present.  Get copy here.

14. D. Dahl-Jensen, K. Mosegaard, N. Gundestrup, G. D. Clow, S. J. Johnsen, A. W. Hansen, N. Balling, Past Temperatures Directly from the Greenland Ice Sheet, Science, 282, 1998

“Dahl-Jensen, et. al., use borehole data to conclude “After the termination of the glacial period, temperatures in our record increase steadily, reaching a period 2.5 K warmer than present during what is referred to as the
Climate Optimum (CO), at 8 to 5 ka. Following the CO, temperatures cool to a minimum of 0.5 K colder than the present at around 2 ka. The record implies that the medieval period around 1000 A.D. was 1 K warmer than present in Greenland.” Get copy here
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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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Melting snows on Mt. Kilimanjaro are not evidence of global warming.

October 13, 2007

Return to Critique of “An Inconvenient Truth” 

What is the extent of Al Gore’s argument that Mount Kilimanjaro, in Tanzania, is an indicator of the effects of global warming? In his book he simple shows a series of three pictures: one taken in 1970, one taken in 2000, and one taken in 2005. The two pictures from 1970 and 2000 are taken from the same angle and thus allow the reader to see a large change in the glacial cover. The entire text consists of 109 words and can be seen in my reproductions of pages 42 through 45 in figures 1 and 2 below.

Figure 1. Reproductions of pages 42 and 43 of An Inconvenient Truth. I have “photoshopped” the images from these pages to make the snow and glaciers stand out more clearly. The obvious point that the reader is supposed to be impressed with is the dramatic decline in snow and glaciers on Kilimanjaro between 1970 and 2000.

Figure 2. Reproductions of pages 44 and 45 of An Inconvenient Truth. I have “photoshopped” the images from these pages to make the snow and glaciers stand out more clearly. The reader is supposed to note the further decline in the glaciers up to 2005. But note that the picture is taken form a different angle than those on pages 42 and 43.

In the movie version of An Inconvenient Truth these same pictures are shown with Al Gore speaking over them saying essentially the same thing seen in the text of the above images. That’s all there is. There are no references to any scientific studies done concerning these glaciers and the possible causes for their retreats. We are simply shown these compelling photographs and the clear impression is left that this shrinkage is caused by CO2 induced global warming.

What does the best science say concerning the glaciers on Kilimanjaro?

Georg Kaser (Tropical Glaciology Group, Department of Geography, University of Innsbruck). et. al., concluded in the International Journal of Climatology in 2004 that since the end of the ice age Kilimanjaro’s glacial extensions and recessions reached their maximum in the Little Ice Age. That is, the glaciers on Kilimanjaro were smaller one or two or three thousand years ago than they were 150 years ago. Then around 1880, long before the atmospheric CO2 concentration showed a significant increase, a climate shift caused them to start receding from their Little Ice Age maximum. On page 336 of the journal article they said that temperature increases “have not contributed to the recession process on the summit so far.”

Philip Mote (Department of Atmospheric Sciences, University of Washington Climate Impacts Group) et. al. said in a recent article in American Scientist, “The observations … point to a combination of factors other than warming air—chiefly a drying of the surrounding air that reduced accumulation and increased ablation—as responsible for the decline of the ice on Kilimanjaro since the first observations in the 1880s.” They continue, “If human-induced global warming has played any role in the shrinkage of Kilimanjaro’s ice, it could only have joined the game quite late, after the result was already clearly decided, acting at most as an accessory…”

Thomas Molg (Innsbruck University Network of Climate and Cryospheric Research) and Douglas Hardy (Climate System Research Center, Department of Geosciences, University of Massachusetts) pointed out in the Journal of Geophysical Research that “it has been speculated that general global warming is directly driving the retreat of Kilimanjaro’s glaciers [e.g., Irion, 2001]. However, detailed analyses of glacier retreat in the global tropics uniformly reveal that changes in climate variables related to air humidity prevail in controlling the modern retreat…”

Gore refers to his “friend, Dr. Lonnie Thompson” and said “He predicts that within 10 years there will be no more ‘Snows of Kilimanjaro.'” But Thompson’s paper Kilimanjaro Ice Core Records: Evidence of Holocene Climate Change in Tropical Africa in the journal Science in 2002 is clearly not a ringing endorsement for Gore’s claim that the recession of Kilimanjaro’s glaciers is due to anthropogenic CO2. In fact, nowhere in the article is the term “CO2″ ever mentioned. Thompson acquired and studied six ice cores from the oldest glaciers near the summit. In the Northern Ice Field (NIF), which supplied the oldest three ice cores (NIF1, NIF2, and NIF3), only one of the cores (NIF3) indicates that its position was covered with ice at the end of the ice age. Thompson’s analysis of the ice core data “suggests that, at ~4 ka [4 thousand years ago], the NIF was smaller than it is today and that the crater-side ice wall likely retreated past the present-day sites of NIF1 and NIF2.” (emphasis added by Moriarty).

Thompsom provides abundant evidence that the climate in tropical Africa has undergone huge and rapid changes multiple times since the end of the ice age (12,000 years ago). For example, 11,000 to 4,000 years ago lakes in the area were up to 100 meters higher than today. Lake Chad in sub-Saharan Africa expanded “from 17,000 km2 to cover an area between 330,000 and 438,000 km2, comparable to that of the Caspian Sea today.” Then it receded back to its present size (17,000 km2) 4,000 years ago when “conditions became cooler and drier.” In fact Thompson states “The Kilimanjaro record documents three abrupt climate changes in this region: at 8.3, 5.2, and 4 ka.” (“ka” means “thousand years ago”).

It is true that Thompson says “if climatological conditions of the past 88 years continue, the ice on Kilimanjaro will likely disappear between 2015 and 2020.” But nowhere in this paper does he even attempt to link the principle drivers of this ice loss to anthropogenic CO2.

Brief look at CO2, temperature and ice extent at Kilimanjaro

Figure 3. Atmospheric CO2 concentration vs. Kilimanjaro ice extent. CO2 data up to 1953 is from the Siple ice core. CO2 data after 1953 is from Mauna Loa, Hawaii. Ice extent for 1880 is from Osmaston, H. 1989. Glaciers, glaciation and equilibrium line altitudes on Kilimanjaro. In Quaternary and Environmental Research on East African Mountains, ed. W. C. Mahaney. Rotterdam: Brookfield, pp. 7-30. Ice extent from 1912 to present is from “Kilimanjaro Glaciers: Recent areal extent from satellite data and new interpretation of observed 20th century retreat rates” Cullen, et. al., GRL 33, 2006

Figure 4. Kilimanjaro summit temperature and ice extent. Ice extent data is the same as figure 3 and the temperature dat is from the National Centers for Environmental Prediction/National Center for Atmospheric Research; compiled by Doug Hardy, University of Massachusetts, Amherst. I have digitized the data from a graph adapted by Tom Dunne.

Return to Critique of “An Inconvenient Truth” 

 

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