Climate change denial in public discourse may encourage climate scientists to over-emphasise scientific uncertainty and is also affecting how they themselves speak -- and perhaps even think -- about their own research, a new study from the University of Bristol, UK argues. Professor Stephan Lewandowsky, from Bristol's School of Experimental Psychology and the Cabot Institute, and colleagues from Harvard University and three institutions in Australia show how the language used by people who oppose the scientific consensus on climate change has seeped into scientists' discussion of the alleged recent 'hiatus' or 'pause' in global warming, and has thereby unwittingly reinforced a misleading message.

The idea that 'global warming has stopped' has been promoted in contrarian blogs and media articles for many years, and ultimately the idea of a 'pause' or 'hiatus' has become ensconced in the scientific literature, including in the latest assessment report of the Intergovernmental Panel on Climate Change (IPCC).

Multiple lines of evidence indicate that global warming continues unabated, which implies that talk of a 'pause' or 'hiatus' is misleading. Recent warming has been slower than the long term trend, but this fluctuation differs little from past fluctuations in warming rate, including past periods of more rapid than average warming. Crucially, on previous occasions when decadal warming was particularly rapid, the scientific community did not give short-term climate variability the attention it has now received, when decadal warming was slower. During earlier rapid warming there was no additional research effort directed at explaining 'catastrophic' warming. By contrast, the recent modest decrease in the rate of warming has elicited numerous articles and special issues of leading journals.

This asymmetry in response to fluctuations in the decadal warming trend likely reflects what the study's authors call the 'seepage' of contrarian claims into scientific work.

Professor Lewandowsky said: "It seems reasonable to conclude that the pressure of climate contrarians has contributed, at least to some degree, to scientists re-examining their own theory, data and models, even though all of them permit -- indeed, expect -- changes in the rate of warming over any arbitrarily chosen period."