Archive for the ‘ice’ 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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TIME for Kids misinforms your children

September 26, 2009

An Arctic Passage 2The modern version of the weekly reader, TIME for Kids, published by the same folks who bring you TIME magazine, heralded the news of the very first ships to sail the legendary “Northeast Passage” in an article titled “An Arctic Passage.”   This route links Europe to the Pacific Ocean, while avoiding the much longer route through the Suez canal and Indian Ocean.  But the reality is that this route was travelled on a regular basis by the Russians from the 1930s to the 1990s.  Read on to see how bogus this propaganda, that was spoon fed to your children, really was.

 

Northeast passage

Northeast passage

Our kids were told very plainly that “It is the first time commercial ships have traveled this route…Shippers have dreamed of a northern shortcut.  right now, ships going from Asia to Europe take a southern route through the Suez Canal, in Egypt.  A northern route would shorten the trip saving time, fuel and money”

This is new, the kids are told, because normally it is “impassable, even in summer, because of packed ice.  But melting ice caps are making it easier for ships to navigate the Arctic.” 

But the real purpose of this article is to keep the drumbeat of global warming fear pounding in the heads of our children.  “Scientists say global warming is responsible for the arctic thaw, which is causing many frozen channels to thaw” they are told.

The Truth about the Northeast Passage from Russia’s  Gubernskaya Academy

As exciting as the above story sounds, it is essentially untrue.  You can read much about the history and exploration of the Northeast Passage as compiled by the Russian Gubernskaya Academy and presented for the International Polar Year.  Here are some of the highlights…

In 1934 the ice-cutter “Litke” made the voyage from Vladivostok to Murmansk without failure by the Northern Sea Route. “Litke” captain was N.M. Nikolaev, research manager V.Yu. Vize. In 1935 four cargo motor ships passed through the Route during a single navigation season.

During the 1930s the Soviets started regular navigated the waters of  the Northeast Passage.  Gubernskaya Academy documents remind us that…

Before the Great Patriotic War [WWII] the Soviet Union gained big experience of carriers navigation in the Arctic. The ports of Dickson, Dudinka, Tiksi, Pevek and Provideniya were under construction. During the war apart from supply of the Arctic construction sites and research stations it was necessary to ensure supply of garrisons and warships and to receive goods delivered from the USA and Canada.

 Ports

Soviet ships would ply the Northeast passage regularly for the next six decades.  Shipping via the Northeast Passage peaked in 1993, but declined after that – not because of ice, but rather cold economic and political winds for the dissolved Soviet Union.

Dissolution of the Soviet Union followed by social and economic crisis of the post-Soviet space in the early 1990’s had a negative influence upon the condition of the Northern Sea Route. The supply system was destroyed due to dissolution of centralized maintenance supply of the Russian North. Due to price liberalization and credit system reconstruction most enterprises in the framework of the Northern Sea Route operation were in a difficult financial state….By 2003 the volume of freight decreased 5 times (1,7 million tons) in comparison with the golden age of the Soviet era.

The two German ships that TIME for Kids referred to are really just the beginning of what the Russians hope will be a revival of trade between Europe, Siberia and Pacific region of Asia:

At present, practical steps are made in Russia to overcome the crisis and to continue development of the Northern Sea Route. This proves high strategic significance of this unique Arctic itinerary. In the first place this high importance is connected with forthcoming development of immense Arctic offshore oil and gas fields. Transit functions of the Northern Sea Route are also of high importance, mainly for development of regions located in the Extreme North and the Far East. Nowadays, many countries of the world are interested in cargo transportation by the Northern Sea Route. This is mainly due to the growing commodity turnover between Europe and the countries of Asian and Pacific regions. Possibly the XXIst century may become an era of intensive development of the Northern Sea Route as of an important arctic transportation passage of national and international importance.

The last ice-cold hard facts

So, these two German ships simply were not the first to make this trip.  In 2000 the Minister of Transportation of the Russian Federation, Sergey Frank, planning for a revival of the trade route, pointed out…

“In 1993 – 1997 the volume of sea cargo along the Northern Sea Route was already 150 – 200 thousand tons a year. Cargo traffic peaked in 1993, during the Arctic’s summer shipping season. During that period, 15 Russian ships with 210 thousand tons of transit goods passed along the Route. Also, 8 ships carrying metals, fertilizers and timber traveled from ports in Russia, Latvia, Sweden and Finland to China, Japan, and Thailand. 7 ships from China carried oilcake, bauxite, magnetite and other operating supplies to Holland, England, Ireland, Germany, and Spain.”

Oh, by the way, TIME for Kids somehow forgot to mention that the two German cargo ships that made the Northwest Passage trip this year were accompanied by a NUCLEAR POWERED ICE_BREAKER!!!  The UK’s Independent,  like TIME for Kids, somehow overlooked the previous 70 years of shipping along the route.  But in the midst of their panic-stricken, end of the world report on this global warming disaster story, they let slip…

The voyage of the two [German] vessels was certainly no picnic. Although not thoroughbred ice-breakers themselves, both ships were designed to cope with ice-strewn waters and were accompanied by at least one Russian nuclear ice-breaker during the whole of the trip. The two ships encountered snow, fog, ice floes, and treacherous icebergs which showed only about one meter of their huge underwater volume on the sea’s surface.

The most challenging stretch of the voyage came at its northernmost point, the Vilkizi Strait on the tip of Siberia. Half of the sea’s surface was covered with pack ice and the captains of both vessels had to call Russian ice pilots on board to shepherd them through. Vlarey Durov, captain of the Beluga Foresight spoke of the stress he experienced from having to keep a constant lookout for ice and the time spent waiting for the seas to clear. (emphasis added)

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DMI Arctic temperature data does show increasing temperature trend

September 9, 2009

I would like to make a few comments about the DMI arctic temperature data.  I made the numeric version of this data available yesterday by digitizing the yearly graphs available from DMI.  I have had a chance to look at the data and draw some initial conclusions.

Anthony Watts, who I have the greatest respect for, presented an animation of the 52 yearly DMI Arctic temperature plots form 1958 to 2009.  He said “See if you can spot the temperature spikes or the “…cooling trend reversed in the mid-1990s.”  His animation appears below…

Anthony Watts animation of DMI temperature plots

Anthony Watts' animation of DMI temperature plots.

As Anthony Watts implied, I found it difficult to detect a trend over time by viewing the animation.  So I created a  simpler version that shows only five frames, each consisting of an overlay of 10 years, 1958 to 1967, 1968 to 1977, …, 1998 to 2007.  The problem is that when I view this simpler animation, I do see a trend, with temperatures rising in the freezing season on the the far left and right sides of the graph in the last frame (1998-2007).  My animation is below (double click is the image does not appear animated)…
Moriarty's animation of 10 year composites of DMI Arctic temperature graphs.

Moriarty's animation of 10 year composites of DMI Arctic temperature graphs.

The data that I made available yesterday gives the DMI Arctic temperature for each half day from 1958 to 2009. This set of data allows a plot of the Arctic temperature for a particular day of the year as a function of the 52 years covered. For example the following two graphs show the temperature on September 1st and October 16th. Notice how the temperature trend seems to increase after 1995 for the October 16th data but not for the September 1st data.
September 1st temperature as a function of year.

September 1st temperature as a function of year.

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October 16th temperature as a function of year.

October 16th temperature as a function of year.

If we are interested in a change of trend after the mid-1990s, then the trend before up to 1995 and the trend after 1995 for every day of the year can be compared in the same way they are compared for October 16th in the above image. The following image shows the temperature trend for each day of the year for 1958 to 1995 and from 1995 to the present.
Arctic temperature trends for each day of the year.

Arctic temperature trends for each day of the year.

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The total trend for each day for all data from 1958 to present is shown in the following graph.
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Arctic temperature trend vs. day of the year for all data from 1958 to 2009.

Arctic temperature trend vs. day of the year for all data from 1958 to 2009.

So, the DMI data, presented in the crude fashion that I have used, lends support to the idea that the Arctic has been heating more rapidly since the mid-1990s than before.  Those of you who have read my blog in the past know where I stand on the probability of the Arctic ice melting in the near future, and I stand by my previous posts.  But I think this data must be presented as part of the scientific pursuit of truth. 
 
I would be very happy to hear the opinions of people smarter than me on the significance of this data.
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Numerical version of DMI Arctic temperature data

September 8, 2009

I am providing the DMI arctic temperature data in numerical format as a public service.  This data is available in graphical format at the DMI Centre for Ocean and Ice,  but I could not figure out a simple  way to get the numerical data that was used to make the graphs.  So I have extracted it from the graphs myself.

Here it is, for the entire set of DMI images from 1958 to the present.  You must go through a slightly convoluted procedure to use it.  First, open this word document.   Then, select all the text and copy it.  Finally, paste it into a spreadsheet.

The left column gives the day of the year.  Notice that the days are given in half day increments.  The top row shows the year, and each column represents the temperature data for the coresponding year.

You can now plot, average, and compare trends to your heart’s content.

Explanation of Data Handling

This data was acquired by copying all of the yearly graphs from DMI and writing image handling code in LabView to extract the temperature data.  The 365 days of data in each graph is distributed through 518 columns of pixels, so about 1.4 columns of pixels per day.  I decided to interpolate the data to half days.  Since leap years and non-leap years both consisted of 518 columns,  I have treated all years as 365.25 days.

All of the data suffers from the uncertainties of my extraction process.  So if anybody sees problems with the data please feel free to post your observations as comments here.

I will be showing some results of my analysis in subsequent posts.

Sample comparison:

Here is the image from DMI for the year 2008, followed by a plot of my version of the data for 2008.

DMI Arctic temperature graph for 2008

DMI Arctic temperature graph for 2008

2008 Arctic data as extracted from DMI image

2008 Arctic data as extracted from DMI image

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2 to 1 odds for Prof. David Barber

August 22, 2009

We are well into summer and the Arctic ice extent and area are taking their annual plunge.  How deep will the plunge be?  David Barber of the University of Manitoba thinks it will be very large.  Just a year ago he predicted that the the North Pole would be ice free in the summer of 2008.  National Geographic reported:

“We’re actually projecting this year that the North Pole may be free of ice for the first time [in history],” David Barber, of the University of Manitoba, told National Geographic News aboard the C.C.G.S. Amundsen, a Canadian research icebreaker.

It turned out that he was wrong. 

The 2008 summer minimum turned out to have more ice than 2007’s minimum. But he has a fallback predicton: that the Arctic Basin will be ice free, at least part of the summer, by 2015.  This is a much more profound prediction.  The North Pole is just  a dot on the map, but the Arctic Basin is 4 million square kilometers surrounding the North Pole. 

Last December I challenged Barber on this blog to wager over his 2015 prediction.  He has not taken me up on the offer.  Now I have doubled the odds for him.  One week ago (8/15/09) I sent him the following email:

Dear Prof. Barber,

I took great interest in your widely reported prediction that the Arctic Basin would see its first ice free summer in 2015. Last December I wrote a blog post in which I challenged you to a wager. That post can be seen here:

 http://climatesanity.wordpress.com/2008/12/10/arctic-sea-ice-gone-by-2015-a-challenge-to-david-barber/

 This post has been viewed thousands of times on both my website and on the sites of others who have re-posted it.

 In that post I said:

“I propose a friendly wager based on this prediction. I will bet David Barber $1000(US) that the ice covering the Arctic Basin will not be gone anytime before December 31st, 2015. The bet would involve no transfer of cash between myself or Barber, but rather, the loser will pay the sum to a charitable organization designated by the winner.

Definition of terms. The Arctic Basin is defined by the regional map at Cryosphere Today. “Gone” means the Arctic Basin sea ice area is less that 100,000 square kilometers, according to National Center for Environmental Prediction/NOAA as presented at Cryosphere Today . Charitable organizations will be agreed upon at the time the bet is initiated.

David Barber is a smart guy and evidently an expert in his field. Taking on a wager with an amateur like me should be like shooting fish in a barrel. I look forward to reaching an agreement soon.”

Perhaps you did not see that challenge online – but many other people did. I am now willing to give you two to one odds on the same wager. Are you interested?

Best Regards,
Tom Moriarty

That’s right.   I will put $2000 dollars against Professor Barber’s $1000.   It should be difficult for him to turn this down.  He can put that $2000 dollars to any good cause that he desires.  If this sum is too small, perhaps we can nogotiate something larger.  He knows how to find me.  But I haven’t had a response yet.

One more point: The Arctic Basin is about 4 million square kilometers that roughly surround the North Pole.  If the Arctic Basin were ice free, then it would be a pretty good bet that all the arctic regions south of the Arctic Basin would also be ice free.  So Barber’s bet that the Arctic Basin will be ice free at some point by 2015 is effectively like saying the entire Arctic will be ice free.    Look at the AMSR-E plots of Arctic sea ice extent below.  Anybody interested in taking my wager?

AMSR-E sea ice extent 090822

Sea Ice extent for the Entire Arctic. If the Arctic Basin becomes ice free, then it is a good bet that the entire Arctic will also be ice free.

Sea Ice extent for the Entire Arctic. Ths is a detail from the graph above. If the Arctic Basin becomes ice free, then it is a good bet that the entire Arctic will also be ice free.

Sea Ice extent for the Entire Arctic. Ths is a detail from the graph above. If the Arctic Basin becomes ice free, then it is a good bet that the entire Arctic will also be ice free.

Why am I making this bet?   Because I am concerned about climate exaggerations and the effect they have on public policy makers. It seems quite clear that David Barber was off the mark when he predicted for 2008 “this year that the North Pole may be free of ice for the first time,” because neither the Arctic Ocean, the Arctic Basin nor the North Pole were ice free in the summer of 2008.  Same with the summer of 2009, so far.  And the Arctic Basin will not be ice free by 2015 either. 

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More on Thermohaline Circulation

June 16, 2009

In a previous post “The Thermohaline Circulation Only Stops for Extreme, Unrealistic Models,” I compared the amount of fresh water used in “hosing experiment” models to drastically reduce the thermohaline circulation (THC, or Meridional Overturning Circulation, MOC) to the amount of water flowing over Niagara Falls, or flowing from all rivers into the Arctic,  or coming off of Greenland due to melting ice.

The key number was one Sverdrup, or 1 million cubic meters of fresh water per second.  One Sverdrup of fresh water artificially dumped into the Labrador sea, for 100 years would have the feared effect.  But it turns out that one Sverdrup of fresh water is 350 times the amount of water flowing over Niagara falls, and about 300 times the amount of water from melting ice that flows off of Greenland.  It was seen that there is not plausible source for this amount of extra fresh water to be dumped into the arctic.

An interesting letter that appeared in Science a year ago gives a little more perspective,  So I have reproduced it in full here:

Freshwater Forcing: Will History Repeat Itself?

IN THEIR RESEARCH ARTICLE “REDUCED North Atlantic deep water coeval with the glacial Lake Agassiz freshwater outburst” (4 January, p. 60), H. F. Kleiven et al. present compelling evidence for an abrupt deep-ocean response to the release of freshwater from glacial Lake Agassiz into the northwest Atlantic about 8400 years ago. Such data are particularly important in evaluating the response in ocean models of the Atlantic Meridional Overturning Circulation (MOC) to freshwater forcing. For this event, the freshwater forcing was likely large but short; Clarke et al. (1) estimate that the flood had a freshwater flux of 4 to 9 Sv [Sverdrups] released in 0.5 years.

In this context, we are aware of no possible mechanism that might reproduce such a forcing in response to global warming, and all available model simulations, including those with estimates of maximum Greenland Ice Sheet (GIS) melting rates, indicate that it is very unlikely that the MOC will undergo an abrupt transition during the course of the 21st century (2). Multimodel ensemble averages under Special Report on Emissions Scenario (SRES) A1B suggest a best estimate of 25 to 30% reduction in the overall MOC strength (2). In one example, 14 coupled models simulated a 100-year 0.1-Sv freshwater perturbation to the northern North Atlantic Ocean—17 times the recently estimated melt rates from the GIS [Greenland Ice Sheet]—and the MOC weakened by a multimodel mean of 30% after 100 years; none of the models simulated a shutdown (3). Another model simulated greenhouse gas levels that increased to four times preindustrial values and then remained fixed; the resulting GIS displayed a peak melting rate of about 0.1 Sv, with little effect on the MOC (4). One model simulation uses the SRES  freshwater forcing as an upper-bound estimate of potential GIS melting. In this case, the MOC weakened but subsequently recovered its strength, indicating that GIS melting would not cause abrupt climate change in the 21st century (5). Accordingly, we urge caution in drawing comparisons of the abrupt change 8400 years ago to future scenarios involving, for example, the melting of the GIS and its relevance to human societies.

PETER U. CLARK1, THOMAS L. DELWORTH2, ANDREW J. WEAVER1
1Department of Geosciences, Oregon State University, Corvallis, OR 97331, USA.
2Geophysical Fluid Dynamics Laboratory/NOAA, Princeton, NJ 08542, USA.
3School of Earth and Ocean Sciences, University of Victoria, Victoria, BC V8W 3P6, Canada.

References
1. G. K. C. Clarke, D. W. Leverington, J. T. Teller, A. S. Dyke, Quat. Sci. Rev. 23, 389 (2004).
2. G. A Meehl et al., in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, S. Solomon et al., Eds. (Cambridge Univ. Press, New York, 2007), pp. 747–845.
3. R. J. Stouffer et al., J. Clim. 19, 1365 (2006).
4. J. K. Ridley, P. Huybrechts, J. M. Gregory, J. A. Lowe, J. Clim. 17, 3409 (2005).
5. J. H. Jungclaus, H. Haak, M. Esch, E. Roeckner, J. Marotzke, Geophys. Res. Lett. 33, 10.1029/2006GL026815 (2006).

So, the event that occurred 8400 years ago involved 4 to 9 Sverdrups of fresh water.  This is THOUSANDS of times greater than the flow of the Niagara Falls today.  It is THOUSANDS of times greater than the amount of fresh water flowing from melting Greenland ice today. It is multiples bigger than the entire fresh water budget into the Arctic.

Note that in my previous post I referred to hosing experiments that pumped up to one Sverdrup of fresh water into the oceans.   The authors of the above letter refer to hosing experiments that used only 0.1 Sverdrups – yet they still point out how gigantic this is compared to actual sources of fresh water in the Arctic today.

So, when Al Gore ominously implies that that the Greenland Ice Sheet [GIS] is going to melt down and dump enough fresh water into the Atlantic Ocean to shut down the Thermohaline Circulation, remember the works of Clarke, et.al., in the above letter: “we urge caution in drawing comparisons of the abrupt change 8400 years ago to future scenarios involving, for example, the melting of the GIS [Greenland Ice Sheet] and its relevance to human societies.”

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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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