It’s official: Andrew Bolt has lost the plot. On his blog on Wednesday, he presented the following graph (using UAH satellite data) as evidence of how “the pause in global warming continues”.

No intelligent person could look at these figures and see anything but a trend towards global warming. Before 1997, world temperatures were predominantly below the 1981-2010 average. After 1997, temperatures are predominantly above the 30-year average. On the instrumental record going back to 1850, there is no precedent for temperatures of this kind, with the decade 2000-09 the warmest on record.

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If one were to draw a trend line through Bolt’s graph, it would slope upwards to the right, confirming warming of the order of 0.5 to 0.6 degrees across the 34-year period. At this rate, climate change will have a substantial impact on ecosystems and economic activity.

What is Bolt going on about? Since early last year, he has been running denialist propaganda, insisting on no warming since 1997. This is a classic exercise in statistical cherry-picking. As the graph shows, temperatures rose in the 1997-99 period due to El Nino. In recent years, weather patterns have experienced La Nina, with a cyclical cooling impact (due to the wet conditions it generates). In Bolt-land, this signifies a pause in global warming.

But climate change cannot be reliably understood or measured by cyclical changes in the weather. It is a long-term trend. Using Bolt’s graph, one could point to massive warming between 2000 and 2010 by cherry-picking those two 12-month periods to exaggerate the extent of temperature changes. But that would not do justice to the trend pattern. It would repeat Bolt’s statistical fraud, but from the reserve side of the argument.

In effect, Bolt has outed himself as a propagandist, hoist on his own petard. By any sensible reading of his graph, there is no pause in global warming. Climate change is real. Just ask the graph on Bolt’s blog — the ultimate condemnation of the denialist position.

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Peter Fray
Peter Fray
Editor-in-chief of Crikey
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