Much ado has been made about global warming stopping since 2001, since 1998 or not increasing in the last decade. Here’s more grist to the skeptic mill. The analysis below shows the global temperature has not increased significantly since July 1979!

Data are from the TLT Satellite measurements of the Earth’s lower troposphere at RSS MSU. When you calculate the global surface temperatures from July to July 1979-2008, the earth has warmed the grand amount of 0.295 degrees C. The standard deviation of the temperature changes for each July to July is 0.2522C, putting the change over 30 years at just over a non-significant one standard deviation (actually p=0.13, significant if p<0.05) of the expected change in just one year. Stated another way, every one out of eight years, global temperature changes by a similar amount to the total increase in the last 30 years.

You have to wonder what all the fuss us about. The effect of 30 years of global warming has been no greater than the change commonly seen in a single year. The data support such low estimates of CO2 doubling as the Spencer climate sensitivity.

The frequency of July-July annual differences with a normal curve (in blue) is plotted using the R language for statistics. The change in temperature from July 1979 to July 2008 is marked as a big red dot. You can see it lies well within the spread of results.

Here is another view of July temperatures over the last 30 years, with the levels of the starting and ending temperatures marked by red dashed lines.

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