The explanatory text can be found in Section 10.3.1 page 762 of AR4, or Page 16 of the pdf. It says "The surface air temperature is used, averaged over each year ..." Follow the link to IPCC AR4Chris Peterson wrote: I have no idea. I don't know where the explanatory text is, or what exactly it says about this image. It is most common for historical and projected data to be presented as a decadal average, but that doesn't mean all data is. There is no way of determining visually if the data on this chart has been averaged decadally or not- that doesn't mean you can't have fine structure in the chart with a period that is arbitrarily short.
I guess I don't really know what your point is.
My point?
The observed global temperature over the last year or so has fallen outside the projections by the models cited in the various IPCC Assessment reports. One would think that on a projection of 100 years that less than ten years out the observed data would fall inside the lines. It hasn't. I don't know why anyone has any faith that there is any degree of accuracy to 100-year projection by these models.