On Nov 22nd I found a problem with 3 of the months of the new GHCN V3 anomaly data available from the NCDC. It appears that the problem was caused by data being missing for certain years for particular months. This led to the data being offset and this caused the set difference stated for the data to be incorrect. As pointed out by other sites this is the type of quality control that is painful to miss.
Now that the problem has been corrected it is possible to take a look at the difference between V2 and the new V3. The results are also interesting, but for a different reason, especially if someone were Skeptical about the goals of the new version. Here is the annual difference between the sets from 1880-present.
Not surprisingly the new version has higher temperatures on an annual basis for every year since 1953. Since 1978 the average annual difference is 0.18 °C. That means that if the new version was put into place as the default, it would shift the warming since then by that amount each year. Even more frustratingly is the period from 1904-1940. That period has an average difference of -0.16 °C. So just the change in versions generates the appearance of 0.34 °C more warming than V2 shows.
If the accumulated difference is shown, the difference is even more pronounced. From 1953-2010 there is more than 8.0 °C accumulated difference, just between the versions. Changing versions will result in the appearance of significantly more warming than V2 has shown. Considering that V2 is already one of the warmest versions, the change will be significant.
Sadly this is not a surprise. That an updated version would show enhanced warming is predictable at this point in the debate. Version 3 will in effect shift the entire temperature record for the past 67 years upwards. That it also decreases the temperature of the period before that only enhances the effect. This is a subtle change, but one that strongly favors the appearance of global warming.