Loehle and Scafetta, Richard Verney comment
I found the paper interesting and so too the comments.
Personally, I cionsider that part of the reason why the AGW ‘theory’ took off was because someone (inappropriately) put a straight fit throgh the temperature records and concluded that there was an upwards trend. when you look at the usual data sets, I cannot see why anyone would seek to put a straight line through the temperatures between late 1800s and to date. Just eyeballing the usual data sets, one see that there are upward and downward trends such that one would either put some sinusoidal line/wave through it or a series of upwards and downwards straight lines.
Whilst correlation does not amount to causation and whilst the causes may be unknown, just eyeballing the usual temperature data sets does suggest that there are factors at play which have some cycular base.
I am one of those people who are very sceptical of the land based temperature record. I consider that it has been so bastersized by adjustments, poor siting, station drop outs, inevitable UHI etc. that it is unreliable. I do not know whether it is warmer today than it was in the late 1800s or 1930s, and I do not consider that the temperature record is sufficiently robust to lay this uncertainty to rest. I consider that it is probably warmer today than it was back in the mid to late 1800s but I would not wish to go more than that nor to put a figure on it. If we are coming out of a LIA, one would expect the temperature to be somewhat warmer and for there to be an overall upward trend since the mid/late 1800s. Is all this natural or is some of it anthropogenic? Again, I am of the view that the data is not robust enough to answer that question. It would not surprise me if changes in land use have had some effect. I would notaltogether rule out pollution or the manmade emissions of GHGs as may be having had some effect but I am very sceptical of this and consider that if this has had an effect it is minor only. To me, the prime suspect behind any real warming is changes in cloud cover which may have reduced albedo and may have allowed the oceans to absorb more solar energy.
Is this study useful in establishing the anthropogenic extent of rising temperatures. Well yes and no as has been pointed out in many of the comments. I would just add that the first two graphs suggest very little in the way of anthropogenic influence.
If on the first graph, one were to put a straight line fit for a 35 year period between 1908 to 1943 (ie., before substantial manmade CO2 emissions) and another straight line fit for a 35 year period between 1960 and 1995 (ie., when manmade emissions are said to be significant), those lines would run parallel to one another and the gradient of the later line would not be steeper than the gradient of the earlier line thereby suggesting that the data does not show an increased rate of warming during the period when there was anthropogenic CO2 emissions. The first graph does not suggest a significant anthropogenic contribution.
Ditto, the second graph. The second graph actually has a straight line running from 1910 to 2010 and the rate of change does not suddenly increase post 1940/1945/1950 (whenever it is claimed that the rapid rise in anthropogenic CO2 emissions took place). The second graph does not support the contention that anthropogenic influence is significant.
I would like to thank the authors for the post and there further comments/replies. An interesting read.