When the mining expert Stephen McIntyre challenged the basis of climate science on his blog, he became a figurehead for many climate-change sceptics.
His subsequent involvement in the 2009 "Climategate" controversy at the University of East Anglia (he was referred to in the hacked emails over 100 times) emboldened the sceptics further and changed global opinion: the number of people who believe man is responsible for global warming has fallen.
The influence might not be positive, but there's no doubt he has shaped the debate.
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