Analysis The story is that the world is heating up - fast. Prominent people at NASA warn us that unless we change our carbon producing ways, civilisation as we know it will come to an end. At the same time, there are new scientific studies showing that the earth is in a 20 year long cooling period. Which view is correct? Temperature data should be simple enough to record and analyze. We all know how to read a thermometer - it is not rocket science.

Previously we looked at how US temperature data sets have been adjusted - with more recent versions of historical data sets showing a steeper rise in temperature than they used to. Here, we'll be looking at current NASA data and why their temperature maps appear hot-red, even when others are cool-blue.

To recap the earlier article, the graph below shows additional adjustments to the data set since the big "correction" in 2000.

We observe that the data has been consistently adjusted towards a bias of greater warming. The years prior to the 1970s have again been adjusted to lower temperatures, and recent years have been adjusted towards higher temperatures.

NASA's published data is largely based on data from the US Historical Climatology Network (USHCN), which derives its data from thermometer readings across the country. According to USHCN literature, the raw temperature data is adjusted to compensate for geographical movements in the weather stations, changes in the 24-hour start/end times when the readings are taken, and other factors. USHCN is directly affiliated with the Oak Ridge National Laboratories' Carbon Dioxide Information Analysis Center, an organisation which exists primarily to promote the idea of a link between CO2 and climate.

The map below shows what the raw unadjusted USHCN temperature trends for the US in the 20th century looked like.  Read rest...