Briffa, Yamal, reputational damage, and all that

@Dave Wendt:

If a tree’s foliage, where all the photosynthesis that builds the tree’s structure, is not at ambient temperature what possible physical mechanism could exist that would allow a tree to encode a precise signal of ambient temperature behavior. That is a question I’ve posed in comments here quite a number of times over the last five years without ever getting an adequate response, or any response at all actually.

Trees (and many other plants) grow based on “degree days”. The Degree Day metric measures when ambient temperatures are in a range above a minimum and below the stagnation temperature (stress temp). Since for many species, the stress temp is well above normal for all but a small number of days, it usually does not apply. (In fact, is substantially ignored outside places like Phoenix Arizona. Something I’ve pointed out for years… The pseudo “panic” being pushed at us about heat hurting crop growth ignores the existence proof of Phoenix. We “lose” a month or two there mid summer to ‘over 110 F’ type temperatures, but in exchange pick up double that much or more on each cool end of the seasons. Check the Sunset Garden book for the growing season graph. Yet even then, the “summer slowdown” is only for SOME species…)
So the tree foliage tries to hold a more stable temperature below the max / stress level; so it can continue to grow (with a 90 F canopy in 110 F ‘weather’). It still racks up the degree days as it’s still growing just fine. On the cold end, transpiration doesn’t give much relief (where it does a great job cooling leaves in the heat). So growth ramps down with cold.
In a way, the growth is like a thermometer that is shut off in the cold, peak clipped in the hot, and rapidly transits from “off” to “full on” in a range from about 50 F to 80F. Other than that, it’s fine 😉
Oh, and if there’s a shortage of water, the transpiration cooling fails and heat stress can cause loss of leaves and truncation of growth for the season much like a freeze can do in the leaves too…
Oh, and in the Pacific Northwest a study found that most of the nitrogen budget of the trees came from bears catching salmon and crapping on the trees; so you must know the bear density and “where they like to poo” to get the nitrogen “flux” right… Tree growth is also a proxy for “bear poo”…
Is that what this meant?:

Latitude says:
Trees can only tell you when it was just right….the tree bears

😉
(Yes, I got the Goldilocks reference…)
@John Tillman:

Sir William Herschel must have been a raving loon to imagine that the sun had anything to do with it.

No. Jevons also studied the effect, and it is real. It just need not be the one you think.
CROP production quantity and prices vary with sunspot cycles.
It could be anything from water variation, to UV changes causing rust outbreaks on the grains or more / less disease among the farmers, to some subtle thing causing folks to get grumpy with the sunspots are down and decide to go on crusades rather than farm.
Furthermore, while Jevons looked at grain figures from places around The Empire (including India) the things you cite were more focused into Northern Europe / Central Europe. In those places the effects of variation in the Gulf Stream are very large. So it could easily be that anything from UV to magnetic to tidal variations from a lunar orbital resonance could be causing cyclical Gulf Stream / Atlantic Drift variations in sync with solar variations. That would then cause those plagues and famines to have the pattern match that was being seen, but ONLY at that end of the Gulf Stream. (In fact, in an article I’ve posted about before, it is shown that Florida gets warmer and the Desert Southwest of the USA gets wetter when Europe goes all cold and miserable from Gulf Stream changes. We win, you lose…)
Please note: I am not saying those potential links of UV et.al. are proven. I’m only pointing out potential alternatives / confounders.
So the first and largest problem with tossing rocks at Herschel and Jevons is to attempt to tar them with a “Global Climate Change” brush when they were in fact only addressing patterns in the data seen in Europe and partly in India. Regional at most. The second problem is to ignore that The Gulf Stream variation might well modulate Europe (and the Monsoon modulate India) in patterns that are solar correlated (and IMHO lunar / tidal driven in orbital resonance sync) while having no effect in other places; or even the opposite effect as demonstrated in Florida pollen / sediments data.
In short: In times of very low sun activity and low sunspots, I’d expect lousy crop years and high grain prices in Europe on average; along with greater cold and miserable wet rains making harvest hard. I’d further expect that to correlate with famine and plagues unless countered with modern food supplies and such. HOWEVER, I’d expect higher yields in the USA “Desert Southwest” (where we grow wheat in Arizona and New Mexico…) and warmer / wetter weather in Florida. So in any modern event, the major effect ought not be famine and plague in England, but a large influx of English tourists to Disneyworld and the French to keep making baguettes but using Arizona grain… 😉
So don’t be tossing Herschel under the bus just yet.