Given how badly labeled it is, I hope to hell you described and explained it in detail in your blog post. Images need to be strongly described in alt and/or longdesc within the img attribute, and described in context, or you’ve created a something that’s useless to people with visual disabilities.
Chronos:
Aside from fluctuations on a scale of ~5 years, trends for GIS, HAD, RSS, and UAH have been steadily climbing, increasing by ~40 since 1979 (see link for graph).
I could do a lot better than that, of course, if I had any clue what that graph meant.
The title is Comparing GISS, HADCRU, RSS and UAH Temperature Records
This is just an update from my post of January 2010 with the source data updated to March 2011 and adding the RSS temperature data to the other three indexes. All four indexes are presented in the form of a 12 month moving average with a linear trend fit through all four datasets. The data is downloaded from http://www.woodfortrees.org/ and imported in Excel and formatted in a way, that in my opinion, more readable. I suggest opening the graph above in a seperate tab to study it in more detail.
A remarkable thing is how closely all four temperature indexes resemble each other when presented this way. The reason I find this remarkable is that these indexes are derived from two independent set of data. HADCRU and GISS use readings from ground based sensors, while the RSS and UAH indexes use satellite data. The resemblance argues strongly for the validity of the data. The satellite data begins in 1979, which is why I use that as the starting year of the graph.
Also note that the slope of the linear fit for all four temperature indexes are similar. They are all within 0.003 degrees centigrade per year of each other. If you project all 4 slopes out for 100 years then the result is 1.37 to 1.65 degrees hotter than now. Of course, a linear projection in this case is almost certainly wrong, but a temperature increase of between 1 and 2 degree centigrade seems reasonable. Standard climate models assume the temperature increase with increases in carbon dioxide is logarithmic rather than linear, so a 1 degree temperature range includes a wide variety of different emission scenarios.
I would think this sort of thing would be common in climate newsletters, except the charts would generally be more complicated or esoteric.