| COMMENTS
TO
LOMBORG´S
PRESENTATION
|
In Lomborg´s text on the Gulf Stream, there is an extraordinary amount of flaws, as demonstrated below. He goes into many details about what various persons have said and written, and in doing this, he repeatedly misrepresents the evidence. If Lomborg´s intention is to present the scientific matter and to assure his reader that there is no imminent risk of a shutdown of the Gulf Stream, he could have done this very easily simply by referring to the latest IPCC report. In that case, he would not have risked to make so many flaws. Why did he not simply do that?
It seems that in addition to assuring the reader that there is no danger, Lomborg has another main agenda. That is to describe how much the whole issue has been misrepresented by many persons, and to paint a picture of a whole bunch of untrustworthy persons, ranging from Al Gore and journalists to many scientists who appear to exaggerate the worries. In other words, the agenda is to create mistrust in the authorities. The available evidence is not enough to do this effectively, and so Lomborg himself exaggerates the unreliability of all opponents.
So the many flaws are not mainly flaws in representing the scientific evidence. They are flaws aiming at putting his opponents in a bad light.
Flaws on
particular
pages in
Lomborgs text:
(COMMENT)
Page 117: "However, according to Gore, climate scientists are now
realizing that the Gulf Stream is "surprisingly fragile".
Comment: Gore may be said
to be right here.
(COMMENT)
Page 117: "About 10,000 years ago, when the last glacial . . . "
Comment: The episode that
Gore is referring to here is the onset of the period called the
Younger Dryas about 11,500 years before present. This event was the
start of a cold period lasting 900 to 1,000 years. It is different from
the episode referred to by Lomborg at about 8,200 years before present.
(COMMENT)
Page 117: "an unprecendented amount of fresh water flooded the North
Atlantic . . . " Comment:
In the previous episode at about 11,500 years ago, which marked the
start of the period called Younger Dryas, the amount of fresh water
released was probably larger.
MISUNDERSTANDING
Page 117 bottom: "For the last and largest event . . . ". Lomborg has
read in the
sources that the event at 8,200 years BP was the largest event.
However, he has overlooked what the sources state, viz. that it
was the largest event in the
Holocene. The Holocene (the present period) started per definion
10,000 years ago. The other events at 12,500 and 11,500 years BP were
much larger than that of 8,200 years BP as regards the drop in
temperature (this drop is known with some certitude) , but they
occurred while the
world was still at the end of the ice age. The event 8,200 years BP may
have been the largest in terms of the amount of fresh water that was
suddenly released (but this amount is not known with certitude). Al
Gore speaks of the event at about 11,500 years BP. The reason why
scientists are so interested in the
smaller temperature drop event 8,200 years ago, is that it set in at a
time when
temperatures were roughly the same as at present.
FLAW
Page 118 top: ". . . the IPCC expects Greenland to dump some 126
km³ of water per year . . . "
Flaw: That amount is
about what Greenland already now dumps per year, as an average of
various studies (A.Cazenave &W. Llovel (2010): Contemporary sea
level rise. Annual
review of marine science 2: 145-173). With rising
temperatures, the annual contribution will of course grow
larger than this. Lomborg´s figure is based on the claim that the
contribution from Greenland to sea level rise will be 3.5 cm. As
explained in the notes to p. 78, this is however the very lowest of all
the IPCC estimates, and it excludes the contribution from increased ice
flow due to lubrication. When Lomborg, as he does here, presents this
figure as if it were a central or authoritative estimate, rather than
the minimum estimate that it actually is, he is deliberately biased.
(COMMENT)
Page 118 top and note 592: " . . some 126
km³ of water per year . . . ". Comment: Lomborg´s
calculation
is
erroneous.
361
million
km²
is
the
total
area
of
water
on
the
globe,
including
fresh
water.
The area of the world´s oceans is
335 million km². Using this correct figure, we get 117 km³
instead of 126 km³. However, this is a minor error and it is not
important, as
the basic assumption of 3.5 cm is biased anyhow. So it is not counted
here as an error.
ERROR
Page 118 top: ". . .almost a thousand times less than what happened in
the story Gore tells us. . . " Error: The amount of water
released
into the sea at the event 8,200 years ago was, according to
Lomborg´s
source, about 200,000 km³. This would suffice to raise the
world´s sea
level by 60 cm. The maximum estimate of how much ice melt from
Greenland could contribute over a century, in case of very rapid global
warming, is also 60 cm (6 mm per year, according to the one of
Lomborg´s sources, Stouffer et al. (2006)). So the fresh water
pulse at
the event 8,200 years ago is not a thousand times the expected fresh
water pulse from Greenland; rather it is about the same size as the
very largest (and not very likely) forecast for the fresh water pulse
from Greenland during 100 years from now on.
However, the event 8,200 years ago is not the story
that Gore told us about. Gore told about the event 11,500 years ago,
when the amount of fresh water released was probably larger.
(COMMENT)
Page 118: ". . . "The possibility of such extreme events precludes
ruling out that disruption . . . ""
Comment: The original
quote, apparently changed somewhat by Al Gore, seems to have been taken
from the following paper: R. Curry & C. Mauritzen (2005): Science
308: 1772 - 1774. This paper ends with the following statement: "The
possibility
of such events precludes ruling out a substantial slowing
or shutdown of the overflows as a result of greenhouse warming."
Readers who
want a more precise explanation of what was meant here are referred
to that paper.
(COMMENT)
Page 118: " . . . if Greenland melted at triple the rate expected by
the IPCC . . . " Comment:
Lomborg gives us the impression that the model study is at the upper
extreme of what the melt rate could be, and probably three times the
most likely melt rate. This is indeed what is stated by the authors.
Actually, concerning the rate of Greenland melt, the authors use a base
scenario (A1B) which yields a contribution to sea level rise of 10 cm
during the 21st century. This is more than the 3.5 cm postulated by
Lomborg, but less than the 25 cm which is the upper range of the IPCC
estimates. A tripling of the basic rate would mean a contribution to
sea level rise of 30 cm during the 21st century. This is approximately
the same size order as the IPCC maximum estimate. In addition, the
authors note that whereas some models are relatively
sensitive to changes in the fresh water fluxes, their model is not so
sensitive. The reasons for such differences between models are not very
well understood. In any case, the effects to be expected are probably
small relative to certain other models.
(COMMENT)
Page 118 bottom: " . . . who put the theory forward one week before the
world met in Japan . . . " Comment:
Lomborg infers that the theory was more or less invented in order to
affect the political process in Kyoto. But Broecker published his
theory in Nature in 1985, more than ten years before the Kyoto meeting.
However, it is true that Broecker did publish another paper in Science
in 1997 at the time of the Kyoto meeting.
(COMMENT)
Page 119 top: "In 2004 Fortune
magazine revealed . . . " Comment:
The article in Fortune did
include certain caveats. It said that scientists generally refuse to
say much about abrupt climate change, citing a data deficit, and it
tells that the scary scenario was produced by non-scientists. It also
says: "It doesn't pretend to be a forecast. Rather, it sketches a
dramatic but plausible scenario to
help planners think about coping strategies."
REMARK
Page 119 top:
"Now the Pentagon tells Bush . . . " Remark: Lomborg is right in
criticising the article in The
Observer, which goes much too far in painting a world-wide
disaster which apparently "will" happen soon.
(COMMENT)
Page 119: "Europe´s climate is more like Siberia´s " Comment: It is obvious from
the part of the text cited by Lomborg that this does not include South
Europe, and on the next page of the document, it is said that this
refers to Northwest Europe. The temperature drop by 2020 is indicated
as 6° F (= 3.3° C).
FLAW
Page 119 bottom: "Yet, the problem with these scary forecasts . . . " Flaw: They are not forecasts.
The authors of the Pentagon report write: "Rather
than predicting how climate change will happen, our intent is to
dramatize the impact climate
change could have . . ". The Fortune article explicitly said "It
doesn't pretend to be
a forecast". And nobody will be in doubt that The Day After Tomorrow
is a piece of fiction, not a forecast.
(COMMENT)
Page 120 top: "But most of northern Europe saw temperatures 0.5-3°
lower . . " Comment: The
authors of the Pentagon report write: "The future
scenario that we have constructed is based on the 8,200 years before
present event, which was much warmer and far briefer than the Younger
Dryas, but more severe than the Little
Ice Age." So the intent was more or less to mimick that event, but of
course the authors were free to construct whatever scenario they
wanted, as long as it agrees with their intention to make a scenario
that, although it is not likely, could happen in principle. They
indicate a temperature drop in NW Europe of about 3.3° C, which
seems within the range of possible actual temperature drops during the
event 8,200 years ago, considering the uncertainty in temperature
reconstructions.
(COMMENT)
Page 120 top: " . . with little effect in southern Europe. For all of
Europe, the difference . . " Comment:
The authors of the Pentagon report write that the temperature
drops do not apply to south Europe, whigh micht even become a little
milder. So Lomborg should not compare "all of Europe" with Siberia.
FLAW
Page 120: "Instead of the 3.5 cm expected for the coming century, they
used 86 cm . . . " Flaw: As
stated
in
comments
to
page
78
and
118,
the
3.5
cm
is
at
the
very
lowest
end
of
the
estimates, which range up to c. 25 cm as the highest. The
authors mention as a very high rate of melting a contribution to sea
level of 6 mm/year, that is 60 cm in 100 years, not 86 cm.
ERROR
Page 120: " . . . they used 86 cm . . " Error: First, there is a small
error of calculation here. Using a correct figure for the area of the
world´s oceans, 335m km², a flow of 0.1 Sv in 100 years will
give a rise of 94 cm, not 86 cm. More seriously, the figure of 86 or 94
cm refers to the flow of all fresh water sources to the North Atlantic,
not just the melt water from Greenland.
The authors state that some of the highest estimates of fresh water
flux for scenarios with 4 X CO2 have a flux from
Greenland of about 0.07 Sv, from melting of perennial arctic sea ice of
0.01 Sv and from other sources of about 0.14 Sv, which yields a total
of 0.22 Sv. However, in the hosing experiment they apply "only" 0.1 Sv.
If we assume that the contribution from Greenland remains nearly one
third, this would be a contribution of 30 cm over 100 years (this is
lower than the highest rate mentioned above, which would yield 60 cm).
A contribution of 30 cm is not very unrealistic, considering that the
top estimate (involving lubrication of ice flow) in IPCC´s 4th
report is about 25 cm, with much uncertainty about the figure.
Note that in the model run, the fresh water flux of 0.1 Sv is applied
only for 100 model years, after which it is switched off. In the real
world, the flux would continue and grow after the first 100 years.
(COMMENT)
Page 120: " . . . the Gulf Stream weakened by 30 % . . ." Comments: One comment to this
is that there were large differences between models. The weakening
varied from 9% to 62%. Another comment is that there were other
important effects than just the temperature change in western Europe.
Most notably, the whole belt of precipitation along the Equator shifted
southwards, e.g. with a reduction of rainfall in the Sahel region of
about 200 mm per year.
(COMMENT)
Page 120: " . . . a cooling over western Europe of just 0.5-1.0°
C." Comment: The paper
says "most of western Europe". The cooling in Britain is 1.0-1.5°
C.
(COMMENT)
Page 120: " . . . one group of modelers find a cooling of the UK by
3-5° C . . . " Comment: The
authors
have
run
a
model
scenario
with
gradual
warming
due
to
CO2 and
then, in 2049, they force a large fresh water pulse onto the model in
order to see what happens when the Gulf Stream then turns off. The
authors write: ". . . scuh a shutdown would return northwestern Europe
in particular to a climate that was substantially colder than
pre-industrial, and the pontential rapidity and unpredictability of
such a change could make adaptation particularly difficult. To put the
predicted temperature drops of up to 3-5° C in perspective, they
mention that during `the Little Ice Age´, average temperatures in
central England were cooled by about 0.5° C. So the model´s
cooling is much, much worse than in the seventeenth and eighteenth
centuries. The reader will not understand this from Lomborg´s
text.
FLAW
Page 120: " . . . the researchers even tried increasing the melt of
Greenland a further ten-fold to 860 cm . . . " Flaw: On page 120,
Lomborg has already reviewed the first part of the paper by Stouffer
et al., in which the apply a fresh water flux of 0.1 Sv, which reduces
the Gulf Stream by about 30 % on average. In the last part of the
paper, Stouffer et al. then apply a fresh water flux of 1 Sv, which
causes the Gulf Stream to shut down nearly or completely in all models
(half of the models have a complete shutdown).
In some models, the Gulf Stream is reversible (it reverts to its
original state after the flux stops); in other models it is
irreversible (it remains in the shut-off state even after the fresh
water flux has
stopped - Lomborg avoids to mention that). In any case, once the Gulf
Stream has stopped, a maximum
cooling of up to 12°C occurs between
Scotland and Iceland, while western and northern Europe becomes 4°
- 10° colder. The experiment is unrealistic - a
fresh water flux of that size is unthinkable - but it serves to show
hos much temperatures could
drop if the Gulf Stream
turned off. Lomborg´s presentation is not correct, because there
is no indication in the model studies that the flux of 1 Sv should come
from melt of Greenland Ice. Rather, the models are especially sensitive
to how much precipitation over the North Atlantic increases per unit of
warming.
GROUNDLESS
DEROGATION
Page 120 bottom: " . . . Al Gore and many others . . . the Gulf Stream
is what keeps European winters some 15-20°C higher . . . " Flaw: Lomborg does not tell
who postulates such at temperature difference of 15-20°. At least
it is not Al Gore. In his book, Al Gore just writes that Paris, London
and Madrid are much warmer than Montreal, Fargo or New York,
respectively. He does not go into any detail about how much warmer, or
in what seasons. And as to the cause of this warming, he writes: ".
. the heat drawn from the Gulf Stream and carried to Europe".
This formulation is correct. As the reader will understand that Al Gore
is incorrect, when he actually is not, this is here desginated as
groundless derogation.
(COMMENT)
Page 121 top: " . . . the predominant wind direction . . . " Comment: The explanation given
here by Lomborg is incomplete. According to C. Wunsch (J. of climate
18(2005): 4374-4380), near the equator, the northward heat transport is
rather evenly divided between heat carried by the ocean current and
heat carried by the atmosphere. North of that, the fraction carried by
the ocean declines. According to van der Swaluw et al. (J. of climate
20(2007): 6023-6032), at 35° N, 22 percent of the heat transport is
by ocean. However, the wind is also crucial in keeping the sea current
flowing, partly because the wind stress pushes the water surface, and
partly because the warm wind causes the hot surface water to evaporate,
thereby increasing the salinity in the surface water; it is this
increase in salinity which allows the sinking of the surface water in
the north Atlantic, and this sinking acts as a pump pulling sea water
northwards. Even as high north as 70° N, there is an important
transfer of heat from the northward flowing water to the atmosphere;
this heat transfer reduces the atmospheric pressure gradient and makes
winds less strong than they would otherwise have been.
(COMMENT)
Page 121: " . . . the MIT ocean physicist Carl Wunsch . . . " Comment: The reader´s
letter that Wunsch wrote to Nature in 2004 was overstated. Wunsch is
right that since the winds will continue to blow and the Earth continue
to turn, the energy source for the Gulf Stream will remain. But as
stated in the general comments on top of this page, this relates only
to that part of the Gulf Stream which stretches up to about
30° N. North of that, the northgoing branch of the current, which
feeds the Meridional Overtruning Circulation, is more sensitive
to changes in various forces, and this branch may be affected by
man-made climate change. See also the comments to Wunsch here.
Furhtermore,
it
remains
true
that
it
is
not
unthinkable
that
the
Meridional
Overturning Circulation may shut down,
as demonstrated by reconstructed prehistoric events and indicated by
certain model
runs.
However, the letter (which was repeated in an issue of the
Economist) made him popular among climate skeptics, and was
probably a main reason why he appeared in the film `The great global
warming swindle´. However, Wunsch subsequently protested against
the way he was used in that film, and the filmmakers had to make a
revised version in which he was cut out. In a declaration printed in
Science no. 328, May 7th 2010, p. 689, it is said that: "There is
complete, comprehensive, and consistent objective evidence that humans
are changing the climate in ways that threaten our societies and the
ecosystem on which we depend." Among the many scientists who signed
this declaration is Carl Wunsch.
(COMMENT)
Page 121 bottom: "Two papers discussed the stability of the Gulf
Stream." Comment: No,
actually, three papers had the Gulf Stream as their main theme. See
comments to page 122 bottom.
(COMMENT)
Page 121 bottom: "The first paper used a simple model of the North
Atlantic Ocean." Comment:
This is only a half truth. The paper consisted of two parts. The first
part used a relatively realistic coupled atmosphere-ocean general
circulation model. The other half used a simple two-box model.
FLAW
Page 121 bottom: "The trick is that with suitable
choices of
set-up,
this box model of the Gulf Stream can easily break down."
Flaw: This is
misleading. The choice of parameters is not set in such a way that the
Gulf Stream shuts down more easily. However, there is a choice of
parameters so that the probability of bi-stability is manipulated. That
is, instead of just having one value of the parameter of wind stress,
the model takes an average of different wind parameter values, and
thereby the probaility of bi-stability is manipulated. That is, we are
dealing with the question of whether the Gulf Stream, once it is forced
to shut down by fresh water addition to the North Atlantic, will be
able to revert to its original state once the fresh water addition
ceases. We are not dealing with the sensitivity of the Gulf Stream to
fresh water addition. Concerning this latter feature, the authors
(Schlesinger et al., p. 46) write: "We calibrated the . . . model
so that it is about as sensitive to a fresh water addition as the
University of Illinois . . coupled atmosphere-ocean genereal
circulation model . . "
(COMMENT)
Page 121 bottom and note 621: "This of course was part of the original
interest in the model . . . " Comment:
The reference in note 621 (from 2005) does not say anything
about the model in the paper in Schlesinger et al. (from 2006) and is
not really relevant at all to the discussion here. The reader may
believe that the reference in note 621 is a documentation for the
postulate about the `trick´ referred to in the preceding
sentence. However, it is completely irrelevant to that sentence.
(COMMENT)
Page 121 bottom: "This model was the original background . . . " Comment: This is not quite
true. The original two-box model from 1961 invariably showed a
bi-stable Gulf Stream, but in 2002 it was amended to
include the gyre circulation in the North Atlantic due to westerly
winds. When this is included, the model is more flexible and may show
either a bi-stable og a mono-stable Gulf Stream, depending on the
intensity of the wind effect. Thus, the criticism from Wunsch that the
effect of westerly winds is ignored, is no longer true.
FLAW
Page 122 mid: "They set up the model such that it sometimes collapses,
sometimes does not . . . " (note 624): " . . . this statement explains
the thrust of the model." Flaw: This is
not true. As explained above with regard to the sentence " The trick is
. . . " on page 121, the model is not set up in a way that has the
effect postulated by Lomborg. Rather, it is adjusted to have the same
probability of a Gulf Stream shut-down as a much more complicated and
realistic model dveloped at the University of Illinois. So, if the
model is biased concerning the probability of shut-down, then this bias
originates from the more complicated and realistic model that is used
to calibrate it, not from the simple two-box model itself.
(COMMENT:)
Page 122 mid:
" . . .
collapses about 50% of the time." Comment: This has little to
do with what the paper actually says. With no mitigation (no tax),
there is about a 46% risk of shut-down in 2100 and about a 69% risk of
shutdown in 2200.
ERROR
Page 122 mid: "They claim that a $27 CO2 tax can reduce
the risk by 28% in 2100." Error:
This is wrong. From reading the curves on their figure 5.7d, one sees
that
the risk is reduced from about 46% to about 28%, that is the risk is
reduced by 18 percentage points, or 39% of the original risk. %. curve
does not agree with the data source. It seems that there is an error in
the
scale on the vertical axis. This original source is found at this
link.
(COMMENT)
Page 122 mid and note 625: "They tell us how a $100 tax is just 50
cents on the gallon . . . " Comment:
First, Lomborg forgets to state that by $100 he means $100 per t
Carbon, equal to $27 per ton CO2. Second, the paper does
not exactly tell that $ 100 per t C is equal to 50 cents on the gallon,
but instead, as said in note 625, that $ 10 is equal to 5 cents per
gallon. It is somewhat misleading in the note to say "They tell us six
times . . . " as if the authors exaggerate their stressing of how low
the amount is. Actually, in their text the authors say that only once.
But Lomborg counts also five places in the graphs where the 5 cent
value is indicated. FLAW
Page 122 mid: " . . . but neglect to tell us . . . essentially shutting
down the fossil fuel economy by 2060." Flaw: Actually, the authors
do show that use of fossil fuels is essentially shut down by 2060. This
is clearly seen in their figure 5.7a. There is no reason why they
should focus particularly on this in their text, as the paper is about
what could happen to the Gulf Stream, not about effects on the global
economy. We have seen above that Lomborg also counts on what is shown
in the figures (the indications of 5 cents per gallon). So, when
Lomborg counts the figures as a part of what the paper says, then his
claim about the shutting down of fhe fossil fuel economy by 2060 is not
correct.
FLAW
Page 122 mid: "In the model the risk reduction is 28%, but . . .
if the risk is much lower - say, close to zero . . . " Flaw: Lomborg fails to state
what he is talking about. Does he talk about the risk of a shut-down in
2100, or in 2200, or when? It is true that in many other models,
the risk of a shut-down already in 2100 is very small, but the risk of
a shut-down in 2200 is much larger. The paper by Schlesinger et al.
mainly discusses the risk of a shut-down in 2200, and according to
their model, this is likely to happen if global temperature by
then increases
by about 2.3° C relative to the year 1900, which is very likely.
Actually, a temperature rise of this order of size might occur already
by 2100. As to the likelihood of a shut-down of the Gulf Stream already
by 2100, this is not referred to in the text, but may be read from one
of the graphs. Here, the probability is about 46% for the no-tax
scenario. As also stated above, with a $100 per t C taxation, the risk
is reduced from about 46%
to about 28%. This is not a 28% reduction.
FLAW OF
OMISSION
Page 122 bottom: "However, it is interesting to realize that, at the
conference, there were two presentations . . . resulting in two
papers." Flaw: Actually,
there were three papes on the stability of the Gulf Stream. The one
omitted by Lomborg is P. G. Challenor, R.K.S. Hankin & R. Marsh:
Towards the probability of rapid climate change, pp. 55-63. This paper
tries to produce a probability distribution of various outcomes
regarding the slowing down of the Gulf Stream. This can be done by
running a good climate model thousands of times with different
combinations of plausible parameter values. However, the computational
power of our computers is not large enough for that. Instead, it is
necessary to run models of intermediate complexity. This has been done,
with 100 computer runs. As seen in the figure below, out of 100 runs,
all but 9 produce an amount of overturning of water in the North
Atlantic in the years up to now of at least 13 Sverdrup, which fits
well with the actual value in the real world. Then, if CO2
emissions during the 21st century follow IPCC´s A1B scenario
(which is likely), the overturning of water is reduced in all runs. Out
of the 91 runs, 37-38 % show a reduction of the overturning to less
than 5 Sv, which will have considerable climatic effects. The result
depends very little on the exact rate of melting of ice on Greenland.
Thus, the result of this type of analysis, which has not been performed
before, is that the risk for a shut-down of the Gulf Stream is much
larger than was anticipated by the authors themselves and by most other
scientists. When Lomborg ignores this paper, his presentation becomes
very biased.
FLAW
Page 122 bottom: "The journalist from the Guardian sat through both,
and even referred to the other in passing. . . " Flaw: The contents of the
Guardian article is grossly misrepresented. The `headline
grabbing´ article by Schlesinger is referred to over c. 12 lines,
whereas the second paper by Wood et al. is referred to over c. 8 lines.
This is a fairly even treatment of the two papers.
FLAW
Page 122 bottom: "But while the headline grabbing first paper used one
simple two-box model . . . " Flaw:
No, it used two models, one of which
was a complicated atmosphere-ocean-genereal circulation model, and the
other was a two-box model which was not very simple.
(COMMENT)
Page 123 top: " . . did a review of the major comprehensive computer
models." Comment: No, it
did not. It referred to the IPCC third assessment report from 2001,
which presented outputs from nine models, representing the state of the
art before 2001.
FLAW
Page 123 top: "The authors pointed out that the shut-off mode
essentially comes from the simple box-models and thus asked if this
instability . . ". Flaw:
This is misleading and not accurate. The reader will understand the
terms `shut-off mode´ and `instability´ as a
situation where the Gulf Stream is shut off. However, the part of the
paper that Lomborg refers to here deals with something else, namely
whether the Gulf Stream is bi-stable (can be led into a new state of
permanent shut-off without reverting) or mono-stable (will revert to
the original state after having been shut off). Simple models, ranging
from two-box models to models of intermediate complexity, often show
bi-stability. Because of computational costs, it is not possible to
explore this in full-size detailed models. Instead, in such models, the
shut-down is forced upon the model, and it is studied whether the Gulf
Stream can revert to its original state. In most complicated models, it
can revert, but in two of the models, it does not revert. On this
basis, to cite the authors, "it is not possible to say definitively
from these model studies whether the present day THC is bistable . . ."
FLAW
Page 123 top: ". . their basic conclusion was straightforward and very
different . . . " Flaw:
Here, Lomborg mixes up two different questions, 1) if the Gulf Stream
circulation is bi-stable or mono-stable, and 2) if the Gulf Stream is
likely to shut down. On neither issue was the conclusion
straightforward. Thus, concerning issue no. 2, the authors write: "In
the present state of scientific knowledge it is not possible to
identify a `safe´ CO2 stabilisation level that
would prevent THC shutdown." They also said that "It should be noted
that none of the [general circulation model] results used in [the IPCC
third assessment report] fully include the effects of melting of the
Greenland ice sheet . . ". This important reservation is omitted by
Lomborg.
(COMMENT):
Page 123 top: "They projected that the Gulf Stream would slow down,
somewhere between 0% and 50%." Comment: Lomborg does not make it clear
to the reader that this concerns what would happen up to the year 2100.
After 2100, the probability of a shut-down is considerably higher.
(COMMENT):
Page 123 top: "No GCMs have shown a complete shutdown . . ." Comment:
What is meant here is none of the GCMs (global circulation models)
referred to by IPCC in 2001. However, the next paper in the book from
2006 (Challenor et al., referred to above) deals with the probability
that a model giving a moderate slowdown as the main result includes the
possibility for a greater reduction or a total shutdown with some
probability. As demonstrated by the figure from Challenor et al.
presented above, even a model with a most likely output of a nearly 50
% slowdown includes a definite possibility that there could be a total
or near-total shutdown. As said above, this paper was ignored by
Lomborg.
FLAW
Page 123: "Thus, the risk of a shut-down was estimated at 50 % by a
two-box model. But when we used the most advanced models . . .
the risk of a shut-down was estimated at zero percent." Flaw: This is a gross
distortion of what the literature says. Most of the two-box models (but
not all of them) show that the Gulf Stream is bi-stable; this is what
they are mainly used to demonstrate. They do not by themselves give any
realistic estimate of the risk that the Gulf Stream will shut down at a
certain temperature. In the paper by Schlesinger et al. that Lomborg
does not like, the calibration of the two-box
model is made by reference to one of `the most advanced models in the
world´. Then, only after this calibration, was it possible to
study what range of parameter choices would lead to a complete
shut-down. The result was then that a shut-down already in 2100 is
likely, and in 2200 very likely.
FLAW
Page 123: " . . . the risk
of shut-down was estimated at zero percent." Flaw: No it was not. The
authors concluded: "The currently very high level of modelling
uncertainty makes accurate projection of the future of the THC
difficult, beyond the rather vague statement that complete shutdown is
`unlikely´ over the next century." `Unlikely´ is not the
same as zero percent.
(COMMENT)
Page 124 top: "National Geographic
told us . . ." Comment: Lomborg
wants
to
give
the
impression
that
several
public
media
try
to
overdramtize
and to scare its readers. Is this impression true? Not
quite. Some media report the story without proper reservations. This
was the case for The Independent.
The Times had an article
focusing on negative news, but did remember to state at the end that
the data from 1992 and 2004 could be mere aberrations. Also, National Geographic remembered to
write that it is too early to say if we are just seeing natural
variability, and that there is no reason for immediate concern. Sydney Morning Herald wrote that
not enough measurements had been made to rule out natural variability. New Scientist (3rd Dec. 2005)
quotes Bryden that he is not yet sure if we see a long-tem trend. BBC News (30th Nov 2005, link)
has
a
large
paragraph
with
the
heading
`Natural
variation´,
stating
that
the
the trend could be down to natural variability.
Altogether, out of six media, only one forgets to mention the necessary
reservations. Considering the usual standard in public media, this is
not very bad.
(COMMENT)
Page 124: " . . . throwing in a reference to The Day After Tomorrow". Comment: The reader will
probably believe that the reference to this film is yet another part of
the sensationalism and scare-mongering. It is nearly the opposite.
Twice in the article, the journalist stresses that The Day After Tomorrow is not realistic. She writes
"Researchers have dismissed the idea the climate would ever change as
rapidly as depicted in The Day After Tomorrow".
(COMMENT)
Page 124: "New Scientist chose it as one of their top stories from 2005
. . " Comment: New
Scientist had a lengthy and not very misleading article on 3rd Dec. In
a review of the main news of the year on 24th Dec. (this is the one
referred to by Lomborg), they had a much shorter notice, in which the
Gulf Stream issue took up only five lines. This short notice mentions
that there is a ´worry´, but does not stress the
uncertainty further than that.
FLAW:
Page 124: Altogether, the whole paragraph starting with "National Geographic told us . . ."
gives an impression of the media coverage which is not accurate and
somewhat misleading.
(COMMENT)
Page 124: "In New Scientist
the headline was . . . ": Comment:
New Scientist had a lengthy article on the subject already on
15th April 2006 by Stephen Battersby.
REMARK
Page 124 bottom: "The Guardian in the UK did report . . .": Remark: In this case,
Lomborg´s criticism seems warranted.
(COMMENT)
Page 125 top: "New Scientist
told us . . . ": Comment: Lomborg
could
also
have
cited
another
sentence
from
that
article
which
is
not
quite as reassuring: "Climate
models
do
not
predict
any
substantial
slowdown
in
Atlantic currents
until near the end of this century."
FLAW
Page 125: "none of the current models simulates an abrupt reduction or
shut-down." Flaw:
Lomborg has truncated the sentence. The original sentence is: "none of
the current models
simulates an abrupt reduction or shut-down in this century." The
missing three words at the end of the sentence are important and should
not have been left out.
ERROR
Page 125 bottom: " . . .IPCC tells that even if the Gulf Stream shuts down
compeletely Europe will still experience warming" Error: The
source for this statement is the 4th IPCC report (its question 10.2),
but IPCC did not exactly say this. Their text is about "a gradual
reduction of the MOC that continues even after climate is stabilised".
As to what will happen in case of a clear-cut shutdown of the northern
branch of the Gulf Stream, we know that Lomborg has
consulted two papers on this issue by Wood et al. from 2003 and
2006. He
ignores what is
said in these. They present a run with one of the advanced models (an
AOGCM), in
which a shut-down of the Gulf Stream is forced upon the model in the
year 2049, following upon the degree of warming that has occurred up to
that point. The result is shown in figures in these papers and is
referred to as follows in the text: "We see that around the North
Atlantic, the cooling effect of the THC change more than outweighs the
effects of global warming, leading to a net cooling relative to the
pre-industrial climate in those regions." and in another place:
". . . such a shutdown would return northwestern Europe
in particular to a climate that was substantially colder than
pre-industrial, and the pontential rapidity and unpredictability of
such a change could make adaptation particularly difficult." To put the
predicted temperature drops of up to 3-5° C in Britain in
perspective, they
mention that during `the Little Ice Age´, average temperatures in
central England were cooled by about 0.5° C. So the model´s
cooling is much, much worse than in the seventeenth and eighteenth
centuries. This part of the
presentation
was also referred to by an article in the Guardian
that Lomborg has read. Considering
that Lomborg has read the papers by Richard Wood et al., and has read
the Guardian article, it is gross sloppiness that he
overlooks this.