Monday 12 October 2009

Because Andrew Bolt brandishes a truncated graph, once more it's time to look at that global warming data again


On Sunday 11 October 2007 journalist Andrew Bolt was a guest on the ABC Insiders program and that gave rise to a post on his News Ltd blog on the same day.

In this post Mr. Bolt presented a graph which he thinks demonstrates that the world has stopped warming and hence there is no climate change going on.

Now that graph (left) apparently came via the Watts Up With That blog from information compiled by Dr. Roy Spenser an anthropomorphic climate change sceptic and supporter of the legitimacy of Intelligent Design Theory.

However, when one looks at NASA graphs of those same years placed within a longer time scale it is obvious that although there are 'plateau' periods the overall global temperature has been steadily trending upwards since at least 1880.
The report of the RSS graph (which relies on the same data as Spenser and Bolt) indicates that there are significant variations within those plateau and NASA points out that past plateau have been known to last for up to 9-10 years in living memory.

"Despite the fact it's been warmer and cooler at different times in the last 10 years, there's no part of the last 10 years that isn't warmer than the temperatures we saw 100 years ago." Josh Willis, NASA, 22 September 2009.

Global Annual Mean Surface Air Temperature Change

Line plot of global mean land-ocean temperature index, 1880 to present. The dotted black line is the annual mean and the solid red line is the five-year mean. The green bars show uncertainty estimates. [This is an update of Fig. 1A in Hansen et al. (2006)] January-September (9 months) mean is used for 2009 data.

(Last modified: 2009-10-06)

Our traditional analysis using only meteorological station data is a lin e plot of global annual-mean surface air temperature change derived from the meteorological station network [This is an update of Figure 6(b) in Hansen et al. (2001).] Uncertainty bars (95% confidence limits) are shown for both the annual and five-year means, account only for incomplete spatial sampling of data. January-September (9 months) mean is used for 2009 data.

(Last modified: 2009-10-06)


While Remote Sensing Systems (RSS) released this satellite derived global chart opposite for September 2009:

According to RSS, September 2009 was warm compared to normal with a global temperature anomaly of +.476 C. Keep in mind, the RSS temperature data covers the latitudes between 82.5 North and 70 South across the globe, so large areas of the polar regions are omitted.
Based on RSS data alone, September 2009 was the warmest month compared to normal since January of 2007 and the warmest September since September of 1998, when the anomaly was +.494 C.

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