RealClimate on the IPCC errors and their significance

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RealClimate has a good post on the recent string of (alleged) errors in the IPCC report. It explains the IPCC proces, the nature and significance of the errors, and highlights the spin put on them by several media outlets.

Excerpt about the reported amount of land in the Netherlands that is below sea level:

Sea level in the Netherlands: The WG2 report states that “The Netherlands is an example of a country highly susceptible to both sea-level rise and river flooding because 55% of its territory is below sea level”. This sentence was provided by a Dutch government agency – the Netherlands Environmental Assessment Agency, which has now published a correction stating that the sentence should have read “55 per cent of the Netherlands is at risk of flooding; 26 per cent of the country is below sea level, and 29 per cent is susceptible to river flooding”. It surely will go down as one of the more ironic episodes in its history when the Dutch parliament last Monday derided the IPCC, in a heated debate, for printing information provided by … the Dutch government. In addition, the IPCC notes that there are several definitions of the area below sea level. The Dutch Ministry of Transport uses the figure 60% (below high water level during storms), while others use 30% (below mean sea level). Needless to say, the actual number mentioned in the report has no bearing on any IPCC conclusions and has nothing to do with climate science, and it is questionable whether it should even be counted as an IPCC error.

 And wrapping up the context of this whole manufacured controversy:

Do the above issues suggest “politicized science”, deliberate deceptions or a tendency towards alarmism on the part of IPCC? We do not think there is any factual basis for such allegations. To the contrary, large groups of (inherently cautious) scientists attempting to reach a consensus in a societally important collaborative document is a prescription for reaching generally “conservative” conclusions. And indeed, before the recent media flash broke out, the real discussion amongst experts was about the AR4 having underestimated, not exaggerated, certain aspects of climate change. These include such important topics as sea level rise and sea ice decline (see the sea ice and sea level chapters of the Copenhagen Diagnosis), where the data show that things are changing faster than the IPCC expected.

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8 Responses to “RealClimate on the IPCC errors and their significance”

  1. tommoriarty Says:

    The tree-ring data that Michael Mann used in his 2008 version of the hockey stick has a worse correlation to temperature than to atmospheric CO2. You can see the details here.

    best regards,
    ClimateSanity

  2. Bart Says:

    Tommoriarty,

    You guys sure like hockey, don’t you? Even if in the end, it’s hardly significant for answering the question of a human contribution to current climate change.

    Please be so kind next time to also provide a link to the paper you’re criticizing.

    Fig 3 is especially interesting. It shows a dozen or so reconstructions of the Northern Hemisphere temperature of the past milennium or two. The pattern amongst them is quite consistent. So if you’re picking at Mann’s reconstruction, you’re picking at pretty much all of them. Good luck and have fun with your multiple hockeysticks.

  3. Scott Mandia Says:

    tommoriarty,

    Perhaps you should read Mann et al. (2008) before you discuss tree ring proxies. When the reconstruction was done WITHOUT tree ring data there was still a hockey stick.

    BTW, despite some claims, the entire paper and all of the supporting information are available free online at:

    http://www.pnas.org/content/early/2008/09/02/0805721105.abstract

    You do not even need an FOI to see the data!

  4. William Connolley Says:

    You might care to weigh in at http://en.wikipedia.org/wiki/Talk:Criticism_of_the_IPCC_AR4#Proportion_of_Netherlands_below_sea_level_is_never_60.25_under_any_definition

  5. Heiko Gerhauser Says:

    http://www.cbs.nl/NR/rdonlyres/D2CE63F9-D210-4006-B68B-98BE079EA9B6/0/2008c167pub.pdf

    Interesting link provided by William. I must admit I am baffled by this. I noticed how some press articles quoted 20%, others said 26%. Do you know a good source that properly explains where these different figures for below NAP come from? Surely one of the two must be wrong, no?

  6. Bart Says:

    Unfortunately I don’t. Many different numbers floating around. Incidentally, NAP isn’t sea level either, and some use the fraction of land below the storm surge level (Rijkswaterstaat I believe).

  7. Heiko Gerhauser Says:

    I think it’s as follows. The CBS round everything between -0.49 and 0 to 0, that gives the 20%. Actual below NAP (ie including -0.01 m and less) is 26%. Mean sea level is close to NAP but differs a bit depending on location, in some places it’s exactly the same as NAP. But NAP used to be average high tide in the IJ 300+ years ago, with average high tide only some 20 cm from average sea level there because tides in the Ij weren’t large (and are non-existant now of course).

    The CBS also give a figure for what’s really threatened by flooding (I think this includes river flooding), namely a third of the Netherlands. That takes account of eg the fact that storm surges can’t reach everywhere to the high storm surge mark at the dike. 60% is below highest ever reached storm surge, but not really indicative of what’s threatened being rather what’s below 5m above mean sea level or so.

    But it would be nice to have an expert explain all this in detail in an article, throwing out plenty of figures is just bewildering.

  8. Bart Says:

    FWIW, I think the current version on wikipedia about the sea level error (called by PBL a “redactionele fout”, i.e. an editing error) is quite balanced: http://en.wikipedia.org/wiki/Criticism_of_the_IPCC_AR4#Proportion_of_Netherlands_below_sea_level
    But then again, much of what I know about this issue comes from the same Volkskrant article and the PBL statement.

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