At a recent dinner, a senior scientific colleague unexpectedly bristled at a comment about anthropogenic global warming, commenting that the world had often seen similar changes to those now being experienced. Four of us in earshot pushed back with attempted jets of cold water, with one saying aghast “you’re sounding like Tony Abbott”.

We all quickly agreed that none of us were expert in all the relevant areas of knowledge and understanding. But this is of course a position that everyone  finds themselves  in daily in regard to any claim in which they are not trained.

So what we all tend to do is to fall in with rule-of-thumb heuristics or cognitive biases that help us make sense of the world. Perhaps the most ubiquitous is confirmation bias  where we seek out, retain and advance facts and assessments  which support our current beliefs.

Anyone with even some elementary scientific background agrees too, that in the evidence pyramid of weakest to strong, the plural of anecdote and opinion does not equal evidence. But when that plurality of opinion manifests as expert consensus, its value is elevated as we see below: here it is reasonable and important to ask how experts across relevant fields view evidence.

Our AGW sceptic that night was convinced he held the knockout punch and the next day sent us a June 2018 swingeing  open letter signed by 25 current Geological Society of London AGW skeptical fellows out of some 12,000, plus another 8 former fellows (with no denominator available to allow a calculation of the proportion). Twenty five of 12,000 is a tiny proportion, heading toward homeopathic territory: 1 in every 480 fellows of the Society. The open letter also referenced a  2010 Royal Society letter of complaint about the RS’s “unscientific” public statements on global AGW. That letter was signed by 43 Royal Society fellows (out of 1600 – 2.7%).

Those derisory proportions don’t say to me that AGW skepticism has much traction in those two most august of scientific communities. Clearly those collecting the signatures would have made efforts to build their lists, yet these small numbers are all they came up with.

In 2015, 76 Nobel Prize winners from across scientific disciplines signed or later fully supported the Mainau Declaration on climate change, which emphasised AGW. The potential Nobel Prize signatory denominator is a much smaller pool, given that the prizes tend to be awarded later in life  and that there are only three categories of scientific prize (physics, chemistry, and physiology or medicine) awarded annually.

Without any apparent self-satire,  the  Geological Society signatories stated “As this letter makes clear [my emphasis] it is not true that 97% of scientists unreservedly accept that AGW theory is fixed, or that carbon and CO₂ are ‘pollutants’ and their production should be penalised.” The authors also asked “how can the primary nutrient in photosynthesis be a pollutant?”  It beggars belief that they could write this when clearly the argument is about the impact of massive rises in CO2, not CO2 itself. Paracelsus’ “the dose makes the poison” is such an elementary principle in toxicology, and it applies to so many exposures and agents.

It’s obviously very far from clear that the arguments of just 35/12,000 geologists destroy the claim that the overwhelming proportion (97%) of climate scientists (working across  many disciplines) accept AGW.

The 97% figure dates from a study published in 2013 of 11,944 abstracts from the peer-reviewed scientific literature on climate change from 1991–2011. The authors wrote:

“We find that 66.4% of abstracts expressed no position on AGW, 32.6% endorsed AGW, 0.7% rejected AGW and 0.3% were uncertain about the cause of global warming. Among abstracts expressing a position on AGW, 97.1% endorsed the consensus position that humans are causing global warming. In a second phase of this study, we invited authors to rate their own papers. Compared to abstract ratings, a smaller percentage of self-rated papers expressed no position on AGW (35.5%). Among self-rated papers expressing a position on AGW, 97.2% endorsed the consensus. For both abstract ratings and authors’ self-ratings, the percentage of endorsements among papers expressing a position on AGW marginally increased over time. Our analysis indicates that the number of papers rejecting the consensus on AGW is a vanishingly small proportion of the published research.”

Since then there have been two further studies that strongly suggest this ballpark is accurate. One (Verheggen et al, 2014) found 90% of those scientists surveyed who had  more than 10 peer-reviewed papers related to climate science agreed with AGW. Another (Powell 2013) looked at 13,950  papers on  global warming and climate change between 1991 and 2012 and found only 24 rejected AGW.

The coalescence of these research findings and expert views is very compelling.

In the fields in which I’ve worked, I’ve seen many examples of attempts by highly motivated, often credentialed people to wreck consensus using Galilean/Copernican metaphors about their brave, truthful voices standing up against the orthodoxy. These include scientists espousing global epidemics of “electrosensitivity” and WiFi & EMR dangers, and anti-vax and  anti-fluoridation drum-bangers.

When these observations are made, we often then hear conspiracy theories  being invoked (“peer reviewers are too threatened by criticism/invested in their own conclusions” etc).

Very few non-specialists are fully equipped to engage in to and fro discussions about arcane oceanography, geophysics, earth sciences etc. What I do is to look to agencies with processes that inspire confidence in scientific integrity and which are transparent about important issues like any competing interests.

I am a strong supporter of renewable energy. We have solar cells all over our roof. Our next car will be electric. I wrote a book on the nonsense of “wind turbine syndrome”.  The arguments for moving rapidly toward  minimally polluting, renewable forms of energy that are producing huge numbers of jobs are self-evident to me. There seem to me to be no serious downsides in harvesting solar, wind, geothermal, hydro- and tidal energy compared to the very real externalities involved in polluting and resource-intensive forms of energy (fossil fuels, nuclear). A couple of weeks living on the east coast of China or Delhi as I have done is a big reality test about the utter folly of  continuing current fossil fuel burning.

Science is never complete, and debate is virtuous. But when debate stalls action, and the consequences of that are highly likely to be catastrophic, prolonging debate instead of acting is irresponsible.