Scientists working on climate on a daily basis must have been rather astonished by the recent interview with professor Fritz Vahrenholt published by European Energy Review (May 2, 2012). Vahrenholt, chief of RWE Innogy, self-proclaimed climate expert and co-author of the book Die Kalte Sonne (The Cold Sun), claims that “the contribution of CO2 to global warming is being exaggerated”. This claim, however, does not stand up to scientific scrutiny. We assess his ideas in the light of the scientific literature on the role of the sun versus other climate forcing factors. The dominant influence of greenhouse gases follows not only from their basic physical properties, but also from their “fingerprint” in the observed warming. The sun, in contrast, has not exhibited any warming trend over the past 50 years. The sun is thus not responsible for the warming seen during this period. Greenhouse gases in all likelihood are.
‘The sun has not exhibited any warming trend over the past 50 years’ (c) Thinkstock
First of all, we welcome the active participation of the business community in the discussion on climate change. Global warming and its effects may have consequences which business, e.g. the energy sector, should anticipate and adapt to. Furthermore, mitigation policies may affect the competitive advantages and business prospects of a variety of energy options. Investment portfolios should take that into account. That is not an easy task. The business consultant or director developing a climate change response strategy may be overwhelmed by the vast amount of – sometimes conflicting – scientific information available. Luckily, every couple of years an integrated assessment is made by the IPCC, the Intergovernmental Panel on Climate Change, primarily aimed at governments, but also quite valuable for the business community.
Of course, opinions differ regarding how well the IPCC assessment reflects the scientific understanding, with some claiming that IPCC overestimates the human contribution to global warming and the risks it poses, whereas others claim that these are underestimated. However, the main tenets of climate science, as described in working group 1 of the IPCC report, have proven to be robust. New research has confirmed the core conclusions, while the details are continuing to be filled in. Vahrenholt’s claim that the IPCC report is radically wrong is unfounded, and is mostly indicative of his views diverging from mainstream science.
This is not to say that no uncertainties remain; of course there are and in some cases they are inconveniently large. Inconvenient, not only because more research is required to further constrain these uncertainties, but also because the uncertainties go both ways. The human contribution to global warming could be somewhat smaller, or it could be somewhat larger than expected. Focussing only on aspects that downplay the anthropogenic contribution is closing one’s eyes to the whole picture.
Challenging the core tenets of climate science is easier said than done. Vahrenholt’s extraordinary claim requires extraordinary evidence. The least one would expect of such a claim is that it be put to the scientific test. Spectacular theories and speculations abound in books and on the internet, but most of
The human contribution to global warming could be somewhat smaller, or it could be somewhat larger than expected
them were not offered to the scientific community, or did not stand up to scrutiny if they were. Scientists routinely check each other’s work via the peer review process, which can be seen as a first test of scientific validity. From further discussions in the literature and other scientific forums the relative robustness of competing ideas is assessed. The most robust idea eventually gains acceptance. That is how science progresses. Surely the peer-review system is not perfect, but at least it is an organised process aimed at filtering what is possibly right from what is plainly wrong. Such a mechanism is lacking in the public debate; and that adds much to the public confusion about this and other complex scientific topics.
Now, would the ideas of prof. Vahrenholt stand up to scientific scrutiny? On the basis of the interview, we expect: no, they would not. However, we would still encourage him to submit his ideas for scientific review. That is where the physical forces and feedbacks in the climate system should be discussed. On the other hand, questions on how society and politics should respond cannot be answered by science, but should be discussed in the public and political debate. Unfortunately, Vahrenholt’s accusations like “we are being misinformed by the climate establishment” and “the whole purpose of the IPCC has been to get rid of the so-called Medieval Warm Period” betray him as being receptive to conspiracy theories, which are routinely echoed on the internet. In such a world view, any criticism by the scientific mainstream is of course only perceived as proof that his and similar views are being suppressed. This is often used as an excuse to not even try to submit one’s ideas to peer review. His book is criticized by scientists not because it would be politically incorrect, as Vahrenholt assumes, but because it is scientifically incorrect.