Guest contribution by Willis Eschenbach
My mind runs to strange corners of the climate issue. I had to think about how little atmospheric CO2 has changed for the most part over the past two thousand years. Here are the CO2 data from ice cores (colored dots) and from the Mauna Loa CO2 measuring stations (red / black line).
Figure 1. Ice core CO2 and Mauna Loa instrumentally measured CO2.
Notice that there is a good match between the thirteen different ice cores and a good match over the period of overlap between the ice core and the instrumental CO2 data.
To see how CO2 has been affecting temperature since the point of the year, I took this CO2 dataset and overlaid it on the Ljundqvist reconstruction of the temperature variability of the extra-tropical northern hemisphere from 30 ° N to 90 ° N. It is a decadal average record that goes from 1st to 1999. I also added in the most recent Berkeley Earth decadal averages for the period since the end of the study for 2000-2009 and 2010-2019. (Since one is a proxy dataset and the other is an instrumental dataset, I adjusted the Berkeley Earth dataset to match the variance of the proxy dataset over the period it overlapped from 1850 to 1999 This is the same procedure that Ljundqvist used in his reconstruction for the black dashed line.)
Here is this graphic.
Figure 2. Ljungqvist decadal temperature reconstruction at 90 to 30 ° N, to which I added ice core and instrumental CO2, as well as the last two decades of Berkeley Earth mean temperatures of 90 to 30 ° N (blue circles). The ice core data are a slight smoothing of the individual ice core data points shown in Figure 1.
In Figure 2 we see the early “Roman Warm Period”, which lasted until around AD 200. Then the temperatures fell until around 500 AD. After that, the world warmed up again to the “Medieval Warm Period”. Then the temperatures cooled down to the “Little Ice Age”, which ended around the year 1700 AD, and finally the temperatures warmed up in attacks and beginnings in the three centuries since the Little Ice Age.
Here are my questions about this historic temperature record:
• Why did the temperature drop after the Roman Warm Period? Why didn’t it just stay warm?
• Why did cooling begin in AD 200 and not AD 600?
• Why did temperatures warm up around AD 550 and continue to warm around the peak of the Medieval Warm Period around AD 1000? It could have stayed cold … but it wasn’t.
• Why did it warm from 550 to 1000 AD and not from around 800 to 1300 AD?
• What caused the constant cooling from around 1000 AD to the depths of the Little Ice Age, where temperatures reached their lowest point around 1700 AD?
• Why did it cool down from AD 1000-1700 and not, for example, AD 1250-1850?
• Why didn’t the world keep cooling to true icing instead of stopping in AD 1700? Given the Milankovich cycles and the length of the other warm interglacials, we are overdue for another true ice age.
• Why did temperatures warm up again at the end of the Little Ice Age instead of just staying at the temperature of 1700 AD?
• Why has it warmed in attacks and beginnings from the Little Ice Age to the present?
Here’s why all of this is important.
NOT ONE CLIMATE SCIENTIST KNOWS THE ANSWERS TO THESE QUESTIONS.
Not one.
And from Figure 2 above it is clear that the answer is not “CO2” …
Without enough understanding of climate to know the answers to these questions, it is absolutely impossible to say that recent warming is not just more natural variations in earth temperature.
In terms of variability, I note in Figure 2 that the extratropical surface temperature of the Earth’s northern hemisphere has hiked around in a range of around 1.5 ° C for the past 2000 years. The surface temperature of the earth is in the order of 288 Kelvin. Including the variance adjustment, this represents a temperature fluctuation on the order of one percent over a period of two thousand years. For me, this is the most interesting thing about climate – not how much it changes over time, but how little it changes.
This thermal stability is not due to thermal inertia – the land in each hemisphere fluctuates around 15 ° C over the course of each year, and the ocean in each hemisphere fluctuates around 5 ° C every year.
I say that this surprising and extraordinary stability is due to the thermoregulatory effect of emerging climate phenomena such as dust devils, tropical cumulus fields and thunderstorms, the El Nino / La Nina mechanism, which pumps excess heat to the poles, tornadoes and hurricanes. I am describing this theory of emergent thermoregulation in a number of posts listed in my 2021 index of my posts here in the Emergence section. These prevent the earth from heating up or cooling down excessively.
In any case, my thoughts recently wandered to the question of two thousand years of temperature and how they are not controlled by CO2 …
Today was sunny and the ground was dry for the first time in a while, so I spent way too much of the afternoon under my truck loosening and removing the RV hold-downs. There is nothing quite like discussing the concept of excessive rotational inertia with an unruly bolt, a bolt where you can only use one hand to turn the wrench to remind a man of his lack of meaning in this wondrous world of miracles glad i own an impact wrench but there are places where it can’t work.
But as the I Ching says, “promotes endurance”, and after using end keys, sockets, breaker bars, deep-walled sockets, two impact wrenches and more than a few bad words, I got it all done.
The best of the sunshine to everyone, life is good
w.
Technical note: Some people have asked is it okay to splice proxy and instrument data, or more generally two sets of data that supposedly measure the same phenomenon?
My answer is absolutely yes IF two conditions are met:
Condition 1: There is enough time overlap between the records to verify that the two records give the same answer. In this case, for example, there is an overlap between instrument and proxy data for both the ice core / instrument CO2 and proxy / instrument temperature records. Figure 1 shows the overlap of the ice core and Mauna Loa CO2. Here is a close up of the overlap between the Ljungqvist temperature and the Berkeley Earth variance adjusted temperature.
Figure 3. Close up, Ljungqvist temperature and variance adjusted Berkeley Earth temperature overlap
In Figures 1 and 3, you can see the overlap, respectively, and make sure that the proxy and instrument records clearly match.
Condition 2: The fact of the splice is made plain and clear without attempting to hide it. In both diagrams the period of overlap is clearly shown and the presence of the splice is also confirmed in the text
Here is a post of mine that covers splicing, appropriately titled “Splicing Clouds”.
Usual notice: I can defend my own words. I cannot defend your interpretation of my words. So if you leave a comment, please quote the exact words to which you are referring.
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