The latest incarnation of the CRUTEM land surface temperatures and the HadCRUT global temperatures are out this week.

This is the 4th version of these products, which have undergone a number of significant changes over that time and so this is a good opportunity to discuss how and why data products evolve and what that means in the bigger scheme of things.

...As expected, the changes (a little from both data sets) lead to a minor rearrangement in the ordering of ‘hottest years’.

This is not climatologically very significant – the difference between 1998 and 2010 is in the hundredths of a degree, and most of the attribution work on recent climate changes is looking at longer term trends, not year to year variability.

However, there is now consistency across the data sets that 2005 and 2010 likely topped 1998 as the warmest years in the instrumental record.

[Much discussion about the data sets and implications here, but in conclusion:]

...All data sets show significant warming over the 20th Century – regardless of whether the raw data comes from the ocean, the land, balloons, ice melt or phenology, and regardless whether the data synthesis is performed by the scientists in Japan, Britain, the US, individual bloggers or ‘sceptics’.