Lomborg-errors: "Cool it!"

Sea level rise
 
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WILL IPCC´s PREDICTIONS HOLD TRUE?

According to satellite measurements, the present level of sea level rise is about 3 mm per year. In hundred years, this will amount to 30 cm. So, when the IPCC predicts a sea level rise of about 30 cm during the 21st century, they actually say that the present rate of rising will continue unchanged. And when they have a lower boundary saying 18 cm, this means that they keep the possibility open that the rate of sea level rise will decrease.This is problematic, because up to now, the rate of sea level rise is faster than what IPCC is able to explain by summing up the known contributions.
    In the most recent (fourth) IPCC assessment from 2007, the scientists have utilised information that was available since the third assessment in 2001, but they have not utilised the very newest information, because they had to go through a time-consuming review process and did not have the opportunity to include the latest evidence. For instance, their predictions  about the extent of melting of the polar sea ice during the arctic summer are already outdated - the extent of melting in 2006 and 2007 has been much larger than predicted by IPCC.
    Another point where IPCC may have underestimated the rate of melting, is the melting of land ice on Greenland and Antarctica. In their calculations, they have included the increased ice flow from Greenland and Antarctica at the rates observed for 1993-2003, but they have not included the further increases in the ice flow observed after 2003.
    The processes governing the rate of discharge of land ice via glaciers into the sea are not fully understood. Information obtained in recent years is that melt water on the surface of the ice may form socalled `moulins´, that is vertical holes through which the water runs to the bottom of the glacier, where it forms a lubricating layer which allows the glacier to slide faster towards the sea. The effect is similar to what is seen in those glaciers whose bottom is below sea level, which means that during periods of high sea water level (tides), the bottom of the glacier is lifted up, which accelerates the outward movement of the glacier ice.
    During recent years, much new information has been gathered on the movements of certain glaciers on Greenland, which are outlets for about 10 % of the total inland ice there. In the Jakobshavn glacier in west Greenland, the velocity of ice movement increased from 1996 to 2000, and increased further from 2000 to 2005. The extent of melting hit a new record in 2007, and altogether the rate of melting during the latest decade was almost twice that of the preceding decade, see this link. In glaciers in mid east Greenland (Helheim and Kangerdlugssuaq) the volocity of ice movement has increased only after 2000. In the latter glacier, the velocity of ice flow has tripled from 2000 to 2005 (data in an article by Rignot and Kanagaratnam, see this link and also this). Such sudden accelerations of glacier flow have not yet happened further north in Greenland, but may come if temperatures continue to increase.
    The point is that IPCC has not foreseen these events, and not included them in their projections. This means that the projected net losses of ice from Greenland and Antarctica are already lower than the actual losses (see this lecture by R. Bindschadler). IPCC has considered the possibility that melt water may increase ice flow by lubricating the glacier bottoms, but they do not  include this effect in their sea level projections, and only notice that this effect may probably give an extra increase of 0.1 to 0.2 m over the century.
    The point is that you may calculate what will happen if ice discharge into the sea grows linearly with temperature rise. But the sudden drastic accelerations in ice flow that have been observed in Greenland after 2000 cannot be incorporated into the mathematical models. One paper has calculated that the contribution to sea level rise from melting Greenland ice has increased from about 0.23 mm per year in 1996 to 0.57 mm per year in 2005 (Rignot and Kanagaratman), but after proper  reductions due to snow accumulation in the centre of Greenland, the net contribution to sea level rise is maybe more correctly estimated at  about 0.04 mm in 2000 and 0.23 mm in 2005. Some others arrive at a contribution of 0.28 mm per year for 2003-2005 (Luthcke et al. 2006), and still others reach estimates of up to 0.7 mm per year for this period (Chen, Wilson & Tapley 2006; references in Cool it).
    Altogether, what happens when the ice on Greenland starts to melt is so complicated that it cannot be simulated properly by mathematical models. This means that nobody knows for sure what will happen. Important facts are 1) that the system does not behave linearly - we see sudden accelerations in ice discharge. 2) The rate of ice loss from Greenland (and Antarctica) seems already to be larger than projected by the linear models of IPCC. The recent acceleration of ice discharge is more than just a random fluctuation due to unusual weather for a few years, but we do not know if it will last - maybe it stops again when the affected outlet glaciers have retreated from the coast line. However, a continued acceleration of ice flow is a definite possibility.
    An important question is if the projected atmospheric levels of CO2 will cause a temperature rise that is sufficient to destabilise the whole inland ice on Greenland and parts of Antarctica. Existing computer models show that a partial or full deglaciation of Greenland may be triggered by even quite modest future increases in CO2 (see this link).Another important question is, if it happens, will we have sufficient time to react? Time passes from the point when greenhouse gases have increased in the atmosphere till the full effect on melting of Greenland ice is seen. And from the time when this is seen, further time passes until the political system wakes up and reacts. The crucial question is if the effects of greenhouse gas reductions appear soon enough to revert the unwanted melting effects.
    Lomborg is sure that we have time enough to react, should this be necessary. Others are not so sure.



RISING SEA LEVELS

Comments to pages 74 - 78 in Cool it.
(COMMENT)
Page 75: " . . . we are engaging in a reckless drive-by drowning . . . ".
Comment:
The quote is correct (see here) but cited out of context. "The rest of the planet" means sites outside USA. McKibben is not talking about floods of many meters, but just flooding of very low-lying lands like Tuvalu and Bagladesh.

(COMMENT)
Page 76 top: "Nonetheless, when using the more than 1,800 tide gauge stations . . ".
Comment:
Figure 20 is based on data from 1,023 tide gauge stations. Data from old time periods are sparse. There are useful data from only 70 stations in 1900, and only 5 in 1850.

(COMMENT)
Page 76 top: "we get the longest data series for sea levelse, as shown in Figure 20."
Comment:
It is no advantage to have a very long time series, because the oldest records are associated with great uncertainty. Before 1870, the uncertainty on the figures is so large that they are nearly useless.

(COMMENT)
Page 76 bottom, note 376: "This is consistent with IPCC, 2007b ch. 5 and generally in the same range as Church & White (2006). . "
Comment:
This is a strange formulation. Lomborg´s data are the same as those in the IPCC report, which are based on the papers cited by Lomborg, such as Church & White (2006).

FLAW
Page 76 bottom, Figure 20 and note 377
Flaw:
The reader who checks the note gets the impression that the sea level curve is the same as depicted by IPCC, only adjusted vertically. But this is not so. The part of the curve that is before 2000 is taken from Jevrejeva et al. (2006), and only the projection is taken from the recent IPCC report. The IPCC concludes that data from before 1870 are too unreliable to be illustrated, whereas Jeverejeva et al. do a greater effort to include as many tide gauge stations as possible, by using certain corrections. The inclusion of more tide gauge stations causes the curve to diverge from the IPCC curve for the period before about 1930. It has a greater upward slope than the IPCC curve. As to the course before 1870, Jevrejeva et al. stress the large uncertainty by indicating a very broad confidence interval (range of uncertainty), and they write specifically that "the large acceleration in sea level 1850 - 1870 coincides with a few new stations becoming active, and is probably not statistically significant." So the temprary drop around 1860 is probably a statistical artifact, which means that the documented rise in sea level is about 20 cm, from the late 19th century to 2000. The rise of 29 cm since 1860 is not reliable, which is stated clearly in Lomborg´s source.
    Lomborg presents a confidence interval (light grey shade) for future values, but omits the confidence interval for the oldest values that are also very uncertain. Instead, he presents a very detailed curve with many ups and downs, which suggest to the reader that the underlying data are very exact and reliable. They are not. This is therefore a deliberately misleading presentation.
    See also the article on sea level rise in Wikipedia.

FLAW
Page 77 top: " . . it is back at around 2.4 mm per year"
Flaw:
This is a biased presentation of the information available. The figure of 2.4 mm is taken from Jeverejeva et al. and is based on data from tide gauges, where the compensation for vertical movements of land masses is incomplete. Satellite measurements, such as those referred to by Lomborg in his note 376, demonstrate a sea level rise of about 3 mm/year for the period 1993-2003. Thus, Lomborg has cherrypicked those values that make sea level rise look smallest. A longer time series of satellite data, covering the period 1993-2008, gives a steady rate of sea level rise of 3.2 mm rise per year, with some ups and downs, but no clear change of the rate (source: this link). Lomborg conceals that the rate of sea level rise is larger than ever before, and his text is therefore very misleading.

FLAW
Page 77 top: "In its 2007 report, the UN estimates that sea levels will rise about 29 cm over the rest of the century . . "
Flaw:
The average for the six scenarios is 34.5 cm. Only the B1 scenario has a central estimate of about 29 cm. It is not acceptable that Lomborg uses just that, because this scenario has the lowest CO2 emission, whereas Lomborg advocates for
nearly no restricitons on CO2 emissions, which would rather correspond to the A1FI scenario with a sea level rise of about 42 cm. As Lomborg should know, the actual development of CO2 emissions is close to the A1FI scenario, or even a little larger.

FLAW
Page 77 top: " . . it is certainly not outside the historical experience"
Flaw:
This is not true.  Allison et al. (2009): Antarctic science 21 (5): 413-426 write: "At about 2000 years before present (BP), sea level rise had almost ceased and, from 1000 yrs BP to the late 19th century, sea level variation was confined within a range of about 0.2m."

FLAW
Page 77: "In its 2007 report, the UN estimates that sea levels will rise about 29 cm . . "
Flaw:
This is a biased statement. The report presents projections for six different scenarios, in which the central estimates range from 28 cm to 42.5 cm. Only one has a  figure below 30 cm.  In addition, the text in section 10.6.5. says explicitly that because not all of the observed sea level rise can be explained up to now, the projections are likely to be underestimates. The report mentions a possible extra contribution of up to 20 cm sea level rise due to melt water lubricating ice flow; this is omitted by Lomborg. Considering that recent information indicates that such lubrication of glacier flow does indeed occur to a hitherho unexpected extent, it is fair to say that the data in the report indicate a sea level rise of probably 50 cm or more.

FLAW
Page 77: "It is also important to realize that the new prediction is lower than the previous IPCC estimates."
Flaw:
This is not true. IPCC WGI paragraph 10.6.5 states that the appraent difference has two reasons: First, the new projections are for 2090-2099, whereas the previous were for 2100. Second, the previous included some small constant additional contributions to sea level rise which are omitted now. . . The previous report would have had similar ranges to those shown now if it had treated the uncertainties in the same way.

FLAW
Page 77 and note 380: "This continues a declining trend from the nineties . . . "
Flaw:
This is not true, which is also evident from the note.