e-letter to Science Magazine
sent: 23 February 2005
Letter Details: N. Oreskes (2004). The scientific consensus on climate change. Science, Vol 306, Issue 5702, 1686, 3 December 2004
Abstract: As requested by Associate Letters Editor Etta Kavanagh,
I have revised and shortened my letter below.
Oreskes (1,2) presents empirical evidence that appears to show a unanimous, scientific consensus on the anthropogenic causes of recent global warming. Oreskes also claims that this universal agreement had not been questioned even once in the peer-reviewed literature since 1993. Her assertion has been extensively reported ever since.
I replicated her study in order to assess the accuracy of its results. All abstracts listed on the ISI databank for 1993 to 2003 using the same keywords ("global climate change") were assessed (3). The results of my analysis contradict Oreskes' findings and essentially falsify her study: Of all 1117 abstracts, only 13 (1%) explicitly endorse the 'consensus view'. However, 34 abstracts reject or question the view that human activities are the main driving force of "the observed warming over the last 50 years" (4).
Oreskes claims that "none of these papers argued [that current climate change is natural]". However, 44 papers emphasise that natural factors play a major if not the key role in recent climate change (5).
The most significant discrepancy with Oreskes' results concern abstracts that are undecided whether human activities are the dominant driving force of recent warming. My analysis shows that a significant number of abstracts reject what Oreskes calls the 'consensus view'. In fact, there are almost three times as many abstracts that are unconvinced of the notion of anthropogenic climate change than those that explicitly endorse it (6).
Even if there is disagreement about any of these papers, it is highly improbable that all 34 are ambiguous. After all, the explicit and implicit rejection is not restricted to individual scientists (7). It also includes distinguished scientific organisations such as the American Association of Petroleum Geologists, which formally rejects the view that anthropogenic factors are the main trigger of global warming:
"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).
Despite this manifest scepticism, I do not wish to deny that a majority of publications goes along with the notion of anthropogenic global warming by applying models based on its basic assumptions. It is beyond doubt, however, that an unbiased analysis of the full ISI databank, which comprises almost 12,000 abstracts, 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, there is no such thing!
In light of the data presented above, Science Magazine should withdraw Oreskes' 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 (http://www.sciencemag.org/cgi/content/full/306/5702/1686)
2. N. Oreskes (2005) Correction. Science, Vol 307, Issue 5708, 355
3. ISI Web of Science, (http://www.webofscience.com/)
4.) Of the 1247 documents listed, only 1117 include abstracts. The 1117 abstracts analysed were divided into the same six categories used by Oreskes, plus two categories (#7,8) which I added: 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. While 29% of the documents implicitly accept the 'consensus view', these papers mainly focus on impact assessments of envisaged 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.
5.) 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.
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. M.E. Fernau at al. stress: "More and better measurements and statistical techniques are needed to detect and confirm the existence of greenhouse-gas-induced climate change, which currently cannot be distinguished from natural climate variability in the historical record. Uncertainties about the amount and rate of change of greenhouse gas emissions also make prediction of the magnitude and timing of climate change difficult", M.E. Fernau, W.J. Makofske, D.W. South (1993) Review and Impacts of climate change uncertainties. Futures 25 (8): 850-863.
7.) "Today, proponents of catastrophic anthropogenic climate change, again claiming scientific consensus, threaten to create even greater energy market distortions at large social and economic costs." H.R. Linden (1996) The evolution of an energy contrarian. Annual Review of Energy and the Environment, 21:31-67.
8) L.C. Gerhard and B.M. Hanson (2000) AAPG Bulletin 84 (4): 466-471.