This is common verbiage:
This study found a detectable change over the 20th century in decadal mean temperatures over each of the six populated continental areas (Europe, North America, South America, Asia, Australia, and Africa), and furthermore found that these changes could only be reproduced with the inclusion of anthropogenic
greenhouse gas emissions.
They did this comparing of the temps to computer models of forcings. Well, that sums up their findings right there. Computer models, nothing more than very expensive "what if" computer games (and I'm a software developer.)
They go on to say:
Jones et al.33 examined summer (June–August) mean temperatures over the past
century over a set of standard subcontinental regions of the Northern Hemisphere. These subcontinental regions divide each of the six continental region into a small
number (between two and six) subregions chosen to represent different climate regimes.34 When signals were regressed individually against the observations,
an anthropogenic signal was detected in each of 14 regions except for 1, central North America, although the results were more uncertain when anthropogenic
and natural signals were considered together.
Ok, we have this data for Canada, let's have a look at July and August temps for all regions. (top line is the highest of the max temp, the upper orange line is the upper standard deviation of the max temps, the black line is the average of the mean, the lower orange line is the lower standard deviation of the min temps and the bottom line is the lowest of the min temps) Thus 65% of the temperature data falls within the upper and lower standard deviations.
From west to east:
BC: BELLA COOLA (Stn 380) Converge in year 2644 at 22C
BC: VICTORIA GONZALES HTS (Stn 113) Converge in year 2850 at 23C
ALB: CALGARY INT'L A (Stn 2205) Converge in year 3100 at 23C
SASK: CHAPLIN (Stn 3080) Converge in year 2681 at 12C
MAN: BIRTLE (Stn 3469) Converge in year 3195 at 14C
ONT: OTTAWA (Stn 4333) Converge in year 2682 at 19C
ONT: LONDON (Stn 4798) Converge in year 3660 at -7C
The rest of the data is far too short, missing records, so how they can possibly justify their claim, with so much missing data, is a mystery.
This study also claims summer temps are increasing, from anthropic forcings, and thus is causing more forest fires: http://www.cccma.ec.gc.ca/papers/ngillett/PDFS/2004GL020876.pdf
The result is clear from the actual station data. The highest of the max temps in the summers (day time highs) in all regions of Canada are dropping. The lowest of the summers (night time lows) are increasing. Thus the range of extreme temps is converging with a meet some 800 years in the future when the nightime and daytime temps would be the same. Since this is NOT physically possible, thus these trends MUST change direction at some time before then and start to diverge. Thus this is only part of a cycle.
Thus this change in summer temps has NOTHING TO DO WITH ANTHROPIC FORCINGS.