One of the surprises I had when I was involved in the Cook et al (2013) paper was how many abstracts there were that hardly mentioned anthropogenic global warming. This was despite them having been selected using the key words global climate change and global warming. When we got to the stage of tabulating and plotting the ratings over the 1991-2011 period, what was even more surprising, to me, was that the proportion of abstracts that took No Position (NP) actually rose from about 50% in the early 1990s to about 65% in 2002, after which that proportion stayed more or less the same for nine years. It wasn’t immediately obvious to me how this squared with the increasing knowledge and generally reduced uncertainties expressed in successive IPCC reports.
The other investigation we did was to ask the authors of the articles to rate their papers on the same scale. Here the overall percentage of NP was lower, about 35%. Not all authors responded to our email queries, so the sample size is smaller than for the abstracts. Also, it was harder to track down email addresses for researchers in the early 1990s, so the sample is particularly small then. Nevertheless, the rising proportion of NP papers is if anything a little more marked here, rising from around 20% in the 1994-1999 period to around 35-40% in the 2001-2011 period.
The difference between abstract and paper NP proportions is not surprising: the abstracts are reserved for key results and the available space there tends not to be wasted telling everyone what the prevailing paradigm is. Also, as confidence in the paradigm grows over time, a larger proportion of papers might consider the attribution of global warming to be an established fact and not something that needs to be endorsed even in the body of the paper itself.
We might well expect to see the same thing in other subjects: for example, life scientists no longer need to affirm evolution through natural selection, it has become settled science; geologists take plate tectonics for granted today, although they would not have in the 1960s when there was a scientific revolution underway. Rising NP proportions in climate science papers, contrary to intuition, might well signify rising confidence among researchers that human emissions are a main cause of global warming—something that just does not have to be reaffirmed every time the subject of changing modern climates is discussed. Continue reading