As I stated - I have not examined the model evidence yet and was examining the historical data set alone.
I agree that the bulk of the evidence points to the current warm, being at least as warm as the two notable past warms, and may indeed be the warmist. I don't think I disputed that even in my first post.
The problem with lack of global coverage in historical proxies is of course real. Kopp et al.2016 uses global sea level changes to attempt to alleviate this. To my eye this supports most local temperature reconstruction pointing to the latest temperature as the most anomalous.
This a one of the reasons why I do not get hung up on the fine details of each study but use an overall sense to what the data is showing. If a factor is important enough it will stand out strongly from the noise.
All this alone does not prove anything beyond the fact that man-made CO2 may have contributed to the recent warm but did not the Roman or Medieval Warm. But it does establish that natural causes have cooled and warm the planet periodically in the last 2 kyr to a similar magnitude than the present warm and that since the recent warm started at least 60 years before man-made CO2 contributions in the mid 1940s, some of the current warming is natural.
Your point 5 is basically the same as my conclusion 2 - examine past climate changes and try to separate the natural from CO2. However where mine was a call for focused examination, you provide a conclusion you find compelling.
'So there is a scientific explanation for natural causes for what warming was seen in the medieval period, which natural causes do not apply today.
While models demonstrate that only greenhouse gas warming can explain current warming.'
Your point has three parts.
1. Conclude what the natural causes where
2. interrogate the present, assess the effect of these natural causes
3. the warming that is left is something else which some authors conclude most likely is man-made CO2 warming.
Total Solar Irradiance never mind volcanic influences for the last 1200 years vary in the literature depending on input data and approach.
Herrera 2013 attempts a TSI power index shown below that roughly correlates with sea level/temp of the Medieval Warm and the Little Ice Age. Upon reaching 1900 it shows a rise in power to a maximum in 1990 then predicts a fall back to his 0 line around 2040. It is one of the best fit I found but of course correlation is not necessarily causality.
I find this compelling evidence that another factor (possibly man-made CO2) produced the raised temperatures we have seen against this lower TSI power.
It is a separate logical argument to conclude what contribution man-made CO2 made to this additional warming. Other arguments are valid and cannot yet be discounted.
- the TSI power variation is wrong predicting the current low. Unlikely due to multiple authors/approaches - the details of the variation of TSI and its 'power' will naturally be refined with more work. A short conspicuous 11 year cycle is recognized by most authors and predicts the same drop in TSI at the start of the 21st Century. So the 'better fit' 120 year cycle does not have to be right to reach the same conclusion about the recent warm.
- other natural factors besides TSI are controlling temperature in recent times. Much more likely since there is at least volcanics/ocean circulation changes and there is always the element of 'we don't know what we don't know'. But for what it is worth, I think man-made CO2 is the most likely suspect but I will keep an open mind.
This brings us back to the 3 step logical way forward - hypothesis (CO2 is the main warming contributor overriding a lowering of TSI power since 1990) -gauge the warming due to the TSI bump in the 20th century, subtract that from the total observed temperature/sea level and estimate the net forcing of CO2.
Use that calibration to run the model forward in time.
This of course is what many authors have done and means getting stuck into understanding the various models which is a daunting but hopefully fruitful task. It may take awhile (work and family get the way).
https://www.researchgate.net/profil...8580cf2dc24b3cc9b2c/Reconstruction-TSI-NA.pdf
View attachment 1118929
Fig. 9 shows these TSI power index anomalies from 1000 to 2100 AD. Negative (positive) anomalies correspond to lower (higher) TSI with respect to the PMOD/ACRIM composites.
