Shaun Lovejoy of McGill University in Montreal had previously developed a statistical methodology that used pre-industrial temperature proxies to analyse historical climate patterns. Using this technique, he ruled out, with more than 99 per cent certainty, the possibility that global warming in the industrial era is just a natural fluctuation in Earth’s climate.
In the present study, he applied this same approach to the 15-year period after 1998. The results suggested that there has been a natural cooling fluctuation of about 0.28–0.37°C since 1998 – a pattern that’s in line with variations that occur historically every 20–50 years. ‘We find many examples of these variations in pre-industrial temperature reconstructions,’ Lovejoy said.
The cooling effect that he observed between 1998 and 2013 also ‘exactly follows a slightly larger, pre-pause warming event, from 1992 to 1998,’ he said. Hence, the natural cooling during the ‘pause’ simply represents a return to the longer-term natural variability. ‘The pause thus has a convincing statistical explanation.’