Dutch assessment of IPCC: “Overall the summary conclusions are considered well founded and none were found to contain any significant errors.”

Dutch foresee much higher sea-level-rise risk than IPCC — and urge IPCC to “to pay attention to ‘worst-case scenarios’. “

Our findings do not contradict the main conclusions of the IPCC on impacts, adaptation and vulnerability related to climate change. There is ample observational evidence of natural systems being influenced by climate change on regional levels. The negative impacts under unmitigated climate change in the future pose substantial risks to most parts of the world, with risks increasing at higher global average temperatures.

The Netherlands Environmental Assessment Agency (PBL) examined the Regional Chapters in the Working Group II portion of the 2007 Fourth Assessment. Full 100 page report is here; Intergovernmental Panel on Climate Change comment is here.


Overall, as the BBC headline makes clear, “Dutch review backs UN climate science report.” So, naturally, the Wall Street Journal headline on the report was, “Dutch Review Raises Concerns About Climate Report.”

Also, there is an effort to spin this report as showing the IPCC has some sort of a bias toward reporting negative impacts.

The Dutch do find a bunch of “very small” errors and one or two medium-sized mistakes, but note:

Realistically speaking, a thousand-page assessment by hundreds of authors involving thousands of reviewers conducted within a limited timeframe could hardly be expected to be free of errors. Therefore, it is to be expected that some inaccuracies, insufficiently justified statements or other irregularities, escape even the most thorough drafting and review procedures.

Interestingly, the PBL actually takes blame for the mistake that actually triggered this review, as the BBC reports:

A furore erupted in the Netherlands over a different claim in AR4, namely that 55% of the country was vulnerable to flooding because it was situated below sea level.

The IPCC attributed the claim to PBL itself, to a report saying that 55% of the Netherlands was prone to flooding.

But that report said only 26% of the country was at risk because it lies below sea level, with the remainder affected by river flooding.

PBL now accepts the blame for the mistake lies within its own doors.

“We acknowledge that this error was not the fault of the IPCC… the error was made by a contributing author from the PBL, and the (co-ordinating) lead authors (of AR4 chapters) are not to blame for relying on Dutch information provided by a Dutch agency,” it said.

And so we have the AP headline — via FoxNews — “Dutch agency admits its mistake in UN report, but says climate change is already happening.”


Because it focuses on even the smallest of errors, the Dutch report makes some odd claims. It finds fault with one numerical range in the IPCC that may not in fact have been in error.

The IPCC said that by the year 2020, between 75 million and 250 million Africans would be at risk of “water stress” (ie not having enough water). PBL says that based on the science available, the figures should be 90–220 million — but that the IPCC projections fit within the “range of uncertainty” in the science.However, Nigel Arnell, head of the Walker Centre at the University of Reading who led the water chapter in AR4, disputed the PBL assessment….

“I think the way in which it was projected with a wide range encapsulated the huge uncertainties, and we think that (narrowing it to) 90–220 million is an over-interpretation of the information that the chapter authors had at the time.”

The report also claims “Examples of negative impacts dominate at summary level.” This is an interesting assertion, but while it may be true in some individual statements, it’s disputable as a sweeping generalization. As I noted here — “The non-hype about climate change (and malaria)” — in the 16-page summary for WGII, here is everything the IPCC says on malaria under the Health Section:

Climate change is expected to have some mixed effects, such as a decrease or increase in the range and transmission potential of malaria in Africa. ** D [8.4]

It is hard to accuse that of being an overstatement of negative impacts

Of course, the UK’s Telegraph has jumped all over this, with “IPCC climate change report ‘played down positive impacts’.” But, as the Dutch make clear, this approach was “approved by the governments that constitute the IPCC,” so it’s hard to accuse the IPCC of doing anything different than what the member governments asked to do.

The Dutch claim has been disputed already:

The Netherlands inquiry adds that the IPCC’s summaries tended to emphasise “worst-case scenarios”.However, this was disputed by scientists who had played a leading role in AR4.“The net impacts of climate change are not beneficial,” said David Vaughan, science leader at the British Antarctic Survey, who co-ordinated the AR4 chapter on polar impacts.

The BBC didn’t actually get this right. If you follow the link the BBC gave to the PBL release, you’ll find this section:

Emphasis on serious, negative impactsPBL Netherlands Environmental Assessment Agency concluded that the summaries in the IPCC Working Group II Report put an emphasis on projections of the more serious, negative impacts of climate change. This selection was an obvious choice, and also had been approved by the governments that constitute the IPCC. However, this meant that the less severe impacts and any positive effects did not make it into the summaries for policymakers, which made the overall tenor of the summaries more negative than that of the underlying chapters. For example, the possibly positive consequences for forestry in North Asia are named in one of the chapters, but they are not named in the summaries.

In addition, the investigated 32 summary conclusions on regional impacts do not mention other factors that play an important role, such as the influence of population growth on water shortages. The PBL recommends to present a broader representation of projected developments in the summaries for policy makers in the Fifth Assessment Reports in 2013 and 2014.

In recent years, more climate change literature has emerged on possible developments with small chances but with potentially large consequences. Therefore, the PBL recommends to pay attention to ‘worst-case scenarios’.

The PBL doesn’t want the IPCC to stop looking at worst-case scenarios. Quite the reverse, it wants the IPCC to explicitly analyze worst-case scenarios, which is precisely what I’ve been saying for quite some time — see “The IPCC lowballs likely impacts with its instantly out-of-date reports and is clearly clueless on messaging “” should it be booted or just rebooted?


What the PBL does want is for the IPCC to have, “One section that describes the projected full range of climate-change impacts, including uncertainties, positive impacts, and the relative contributions from other important areas, such as industrialisation, population growth, and land use” and “One section that describes the most important negative impacts, includinga worst-case risk approach, based on a clearly explicated risk-assessment methodology.” Great idea!

Indeed, on the crucial issues of sea level rise and carbon cycle feedbacks, the IPCC not only didn’t “Accentuate the negative” as the Economist tries to spin things, it largely ignored the negative and spun out best case scenarios. Moreover, in a AAAS presentation this year, William R. Freudenburg of UC Santa Barbara discussed his research on “the Asymmetry of Scientific Challenge”:

New scientific findings are found to be more than twenty times as likely to indicate that global climate disruption is “worse than previously expected,” rather than “not as bad as previously expected.”

So the charge that the IPCC has a negative bias is patently false. It appears that, to paraphrase Stephen Colbert, reality has a negative bias.


The most interesting part of this entire report, to me, is “Annex D Sea level rise: consequences for the Netherlands.” Needless to say, the Dutch are worried about sea level rise. So it’s no surprise that they’ve spent a lot of time looking at the risk — and no surprise they never entirely bought into the absurd low-ball estimate of the IPCC’s Fourth Assessment (AR4) — see Scientists withdraw low-ball estimate of sea level rise “” media are confused and anti-science crowd pounces.

Annex D says:

When considering the possible sea level rise for the Netherlands, the most recent estimates on sea level rise for the Netherlands cover a range of 35 to 85 cm for 2100 (KNMI, 2006), or in case of high-end/worst-case estimates, the rise is between 130 cm (Deltacommissie, 2008) and 150 cm (PBL, 2007).

Note that even the old 2006 Dutch estimate exceeded the 2007 IPCC’s high scenario of 26 to 59 cm SLR. Annex D continues:

In 2007, in collaboration with the Royal Netherlands Meteorological Institute (KNMI), the PBL explored plausible future extreme sea level rise scenarios for the Netherlands and — based on paleoclimatological data — estimated a worst-case sea level rise of 1.5 m/century (PBL, 2007). Given the technical adaptive capacity of the Netherlands and the considered safety margins, the PBL concluded that, with the available techniques, the delta region of the Netherlands could be kept safe even in case of such an extreme sea level rise, but that in the long term, spatial measures could be required (PBL, 2007). In 2008, the Dutch Delta committee (Deltacommissie) presented a high-end estimate on sea level rise of between 65 and 130 cm for 2100, based on a temperature-rise scenario of 6 degrees, and also concluded that technically the delta region of the Netherlands could protect itself against flooding (Deltacommissie 2008). The maximum ranges for sea level rise given by the IPCC (2007) and the KNMI (2006), were based on scenarios with a maximum of 4 degrees temperature rise. A 6-degree temperature rise thus exceeds the 4-degree scenario of the IPCC, but still lies within the total range of uncertainty

Ironically, while the Dutch urge the IPCC to focus on worst-case scenarios, they haven’t really done so themselves — see “Sea levels may rise 3 times faster than IPCC estimated, could hit 6 feet by 2100 (which is the source of this figure):


The notion that the worst-case scenario for sea level rise is 1.5 m/century is now, I think, patently absurd. Also, it confuses the amount of sea level rise we might see this century, with what the rate of sea level rise would have to be in 2100 to make that possible.

The plausible worst-case scenario for SLR by 2100 is much closer to 2 meters, as Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research (and coauthor of the research behind the above figure) confirmed with me by e-mail today (see also “Startling new sea level rise research: “Most likely” 0.8 to 2.0 meters by 2100“). And that would mean a much higher rate of sea level rise in 2100 than 1/5 m/century. The 2-meter estimate does presuppose that we are assuming no significant possibility of a major collapse of the West Antarctic ice sheet.

This is a complicated subject and this post is already long enough, so I’ll come back to it shortly.

The bottom line of the Dutch report is clear:

  1. “The main conclusions of the IPCC on impacts, adaptation and vulnerability related to climate change” stand: “There is ample observational evidence of natural systems being influenced by climate change on regional levels. The negative impacts under unmitigated climate change in the future pose substantial risks to most parts of the world, with risks increasing at higher global average temperatures.”
  2. The IPCC should focus more explicitly on worst-case scenarios.
  3. While some parts of the IPCC summaries emphasize negative impacts — as the governments have asked them to — as a whole, the IPCC reports are conservative documents as more recent research confirms.