Came across this rather amusing snippet in the Metro’s MiniCosm column, and felt it deserved slightly wider coverage, thought a quick search does show it’s being picked up quite well once you know to search for it (“sheep tree rings”)
The minicosm article says:
“For more than 100 years, tree rings have been used to record climate. But nibbling from sheep could have had more of an impact on their development than historic changes in the weather. After spending nine summers in pens with sheep, cross sections of 206 birch trees were measured. Tree ring widths were more affected by the number of sheep around than the ambient temperature at the site, Scottish and Norwegian scientists found. ‘The density of herbivores affects the tree ring record, at least in places with slow-growing trees” they said.”
A more in depth article can be found over on escience news. Which also notes that:
“Many factors in addition to climate are known to affect the tree ring record, including attack from parasites and herbivores, but determining how important these other factors have been in the past is difficult.”
So the “settled science” is based on an indirect indicator of temperature which is largely affected by non-climate related factors which can in themselves only be indirectly estimated:
“The good news is that past densities of herbivores can be estimated from historic records, and from the fossilised remains of spores from fungi that live on dung.”
And which judging from this study they’ve only just started to disentangle – now obviously this doesn’t disprove anything, well except that maybe the science isn’t actually settled. Though of course as LegIron is won’t to observe the moment anyone claims that the science is settled they’ve ceased doing science.
