This is an ultrasimplified version of Doug Keenan's post this morning.
The Met Office has consistently said that the temperature rise since 1850 is too large to have been caused by natural causes. Questioning from Lord Donoughue elicited the information that they came to this conclusion by modelling temperatures as a straight-line trend (global warming) plus some noise to represent normal short-term variability.
However, would a model in which temperatures went up and down at random on longer timescales, but without any long-term trend at all, be a better match for the real temperature data? Doug Keenan has come up with just such a "temperature line wiggling up and down at random" model and it is indeed a much better match to the data than the "gradual warming plus a bit of random variation" model used by the Met Office. In fact it is up to a thousand times better.
In essence then, the temperature data looks more like a line wiggling up and down at random than one that has an impetus towards higher temperatures.* That being the case, the rises in temperature over the last two centuries and over the last decades of the twentieth century, look like nothing untoward. The global warming signal has not been detected in the temperature records.
*Here I'm only referring to the two models assessed. This is not to say there isn't another model with impetus to higher temperatures which wouldn't be a better match than Doug's model. It's just nobody has put such a )third model forward yet. (H/T JK in the comments)