It turns out that there is no way to reliably compare current global temperatures to historical data using NASA's database.  It is a scientific scandal.

I wrote recently about NASA changing its entire temperature record database, just from July to September. That is, in 2012, NASA changed temperatures going back to 1880. And it did that without telling anyone or explaining it. The net effect was to make the 130-year warming trend steeper, by lowering older (pre-1963) temperatures and slightly raising recent ones.

I must confess, I was slightly apprehensive about writing that. It was just possible that I had grabbed the wrong data set in July and was comparing apples and oranges. I'm now happy to report that I was not the only one to catch this change. It was real.

I don't know exactly who does this, or how, but someone compares every month of NASA's temperature data to the previous month. If you want to see exactly what changed between August and September 2012, select the top month on that page. Here is a summary of how much changed in recent months.

• August to September: 60%.
• July to August: 27%.
• June to July: 17%.
• May to June: 39%.
• April to May: 17%.

NASA's temperature record is, indeed, a living document.

My piece was also picked up by "Watts Up With That?" WUWT argues that NASA is in violation of the Data Quality Act.

This is the data that the American public pays for. It is one of only two or three such records of global temperatures going back more than a century. It is what all claims of global warming are based on. And about one third of that data changes every month! Without warning, notice or explanation.

In my opinion, this is a scandal. There is no way for the public to inform itself reliably on an issue that could cost us trillions of dollars. We have no way of knowing how much of global warming is real and how much is simply due to unexplained adjustments to the data - data that is under the control of zealots like James Hansen.

Randall Hoven can be followed on Twitter or contacted via his web site, randallhoven.com.