Wednesday, April 11, 2007


Benny Peiser debunks Naomi Oreskes' claim of SCIENTIFIC CONSENSUS that humans are responsible for global warming. Any bold print is my addition.

Dr. Peiser's letter to the journal Science:

On December 3rd, only days before the start of the 10th Conference of Parties of the United Nations Framework Convention on Climate Change (COP-10), Science Magazine published the results of a study by Naomi Oreskes (1): For the first time, empirical evidence was presented that appeared to show an unanimous, scientific consensus on the anthropogenic causes of recent global warming.

Oreskes claims to have analysed 928 abstracts she found listed on the ISI database using the keywords "climate change". However, a search on the ISI database using the keywords "climate change" for the years 1993 - 2003 reveals that almost 12,000 papers were published during the decade in question (2).

What happened to the countless research papers that show that global temperatures were similar or even higher during the Holocene Climate Optimum and the Medieval Warm Period when atmospheric CO2 levels were much lower than today; that solar variability is a key driver of recent climate change, and that climate modeling is highly uncertain?

These objections were put to Oreskes by science writer David Appell. On 15 December 2004,
she admitted that there was indeed a serious mistake in her Science essay. According to Oreskes, her study was not based on the keywords "climate change," but on "global climate
change" (3).

Her use of three keywords instead of two reduced the list of peer reviewed publications by
one order of magnitude (on the UK's ISI databank the keyword search "global climate
change" comes up with 1247 documents). Since the results looked questionable, I decided to
replicate the Oreskes study.


I analysed all abstracts listed on the ISI databank for 1993 to 2003 using the same keywords ("global climate change") as the Oreskes study. Of the 1247 documents listed, only 1117 included abstracts (130 listed only titles, author(s)' details and keywords). The 1117 abstracts analysed were divided into the same six categories used by Oreskes (#1-6), plus two categories which I added (# 7, 8):

1. explicit endorsement of the consensus position
2. evaluation of impacts
3. mitigation proposals
4. methods
5. paleoclimate analysis
6. rejection of the consensus position.
7. natural factors of global climate change
8. unrelated to the question of recent global climate change


The results of my analysis contradict Oreskes' findings and essentially falsify her study:

Of all 1117 abstracts, only 13 (or 1%) explicitly endorse the 'consensus view'.

322 abstracts (or 29%) implicitly accept the 'consensus view' but mainly focus on impact
assessments of envisaged global climate change.

Less than 10% of the abstracts (89) focus on "mitigation".

67 abstracts mainly focus on methodological questions.

87 abstracts deal exclusively with paleo-climatological research unrelated to recent
climate change.

34 abstracts reject or doubt the view that human activities are the main drivers of the
"the observed warming over the last 50 years".

44 abstracts focus on natural factors of global climate change.

470 (or 42%) abstracts include the keywords "global climate change" but do not include any
direct or indirect link or reference to human activities, CO2 or greenhouse gas emissions,
let alone anthropogenic forcing of recent climate change.


According to Oreskes, 75% of the 928 abstracts she analysed (i.e. 695) fell into these first three categories, "either explicitly or implicitly accepting the consensus view". This claim is incorrect on two counts: My analysis shows that only 424 abstracts (or less than a third of the full data set) fall into these three categories.

It also shows that many abstracts on "evaluation of impact" and "mitigation" do not discuss which drivers are key to global climate change, instead often focusing exclusively on the possible effects of elevated CO2 levels on plant growth and vegetation.

Many do not include any implicit endorsement of the 'consensus view' but simply use certain assumptions as a basis for often hypothetical impact assessments or mitigation strategies. Quite a number of papers emphasise that natural factors play a major if not the key role in recent climate change (4). My analysis also shows that there are almost three times as many abstracts that are sceptical of the notion of anthropogenic climate change than those that explicitly endorse it (5, 6, 7). In fact, the explicit and implicit rejection of the 'consensus view' is not restricted to individual scientists. It also includes distinguished scientific organisations such as the American Association of Petroleum Geologists: "The earth's climate is constantly changing owing to natural variability in earth processes.

Natural climate variability over recent geological time is greater than reasonable estimates of potential human-induced greenhouse gas changes. Because no tool is available to test the supposition of human-induced climate change and the range of natural variability is so great, there is no discernible human influence on global climate at this time" (8)

This is not to deny that there is a majority of publications that, although they do not empirically test or confirm the view of anthropogenic climate change, go along with it by applying models based on its basic assumptions. Yet, it is beyond doubt that a sound and unbiased analysis of the full ISI databank will find hundreds of papers (many of which written by the world's leading experts in the field) that have raised serious reservations and outright rejection of the concept of a "scientific consensus on climate change". The truth is, that there is no such thing!

In light of the data presented above (evidence that can be easily verified), Science should withdraw Oresekes' study and its results in order to prevent any further damage to the integrity of science.

1. N. Oreskes (2004). The scientific consensus on climate change. Science, Vol 306, Issue
5702, 1686, 3 December 2004 (
2. ISI Web of Science (
4.) C. M. Ammann et al., for instance, claim to have detected evidence for "close ties
between solar variations and surface climate", Journal of Atmospheric and Solar-
Terrestrial Physics 65:2 (2003): 191-201. While G.C. Reid stresses: "The importance of
solar variability as a factor in climate change over the last few decades may have been
underestimated in recent studies." Solar forcing of global climate change since the mid-
17th century. Climate Change. 37 (2): 391-405
5) H.R. Linden (1996) The evolution of an energy contrarian. Annual Review of Energy and
the Environment, 21:31-67.
6) Russian scientists K. Kondratyev and C Varotsos criticise "the undoubtfully
overemphasised contribution of the greenhouse effect to the global climate change". K.
Kondratyev and C Varotsos (1996). Annual Review of Energy and the Environment. 21: 31-67
7) M.E. Fernau, W.J. Makofske, D.W. South (1993) Review and Impacts of climate change
uncertainties. Futures 25 (8): 850-863.
8) L.C. Gerhard and B.M. Hanson (2000) AAPG Bulletin 84 (4): 466-471
From: []
Sent: 04 January 2005 11:07


Research Papers Writing said...

Many institutions limit access to their online information. Making this information available will be an asset to all.

Michael said...

Oreskes is now in australia for the Sydney Writers Festival (read "lefty love in"). She is pushing her book on this very study but she made no mention of these inaccuracies???

What is wrong with the world that they don't know this?