Guest post by Renee Hannon
Introduction
The Arctic and Antarctic regions are different and yet similar in many ways. The Arctic has ocean surrounded by land and the Antarctic is a continent surrounded by water. Both are cold, glaciated and located at Earth’s poles some 11,000 miles apart. While sea ice has been retreating in the Arctic, it has been relatively stable in the Antarctic. This post examines surface temperature trends, solar insolation, and CO2 at the polar Arctic and Antarctic regions during the Holocene interglacial period.
Holocene Polar Temperature Trends are Out of Phase
The Holocene interglacial started about 11,000 years ago after termination of the previous glacial period. It is commonly described as consisting of an early Holocene climate optimum from approximately 10,000 to 6,000 years before present (BP, before 1950). This optimum is followed by a pronounced cooling in the mid-late Holocene referred to as the Neoglacial period which culminates in the Little Ice Age (LIA) around 1800 years AD (Lui, 2014).
Past Holocene temperature anomalies are typically estimated from ice core proxies. This post uses Arctic temperature anomalies from Agassiz-Renland isotope data corrected for elevation by Vinther, 2009 and Antarctic temperature anomalies from Dome C ice core proxies calculated by Jouzel, 2001. Temperatures are presented as anomalies relative to present day average polar temperatures. Time is shown as both years AD/BC and years before present, BP. Years BP (yr BP) is the key reference in the text. Datasets used are referenced at the end of the post.
Arctic and Antarctic Holocene temperature anomalies are shown in Figure 1. Arctic temperature anomalies show a prominent climate optimum from 10,000 to 6,000 yr BP with a brief cold interruption around 8,200 yr BP. The Neoglacial cooling is also evident where Arctic temperature anomalies steadily cool from 6,000 yr BP to the LIA as described in the literature.
The Antarctic seems to be a bit more contrary from the simple Climate optimum and Neoglacial description. Antarctic does exhibit a temperature high or optimum from about 11,500 to 9000 yr BP. Masson, et. al, 2000, examined all existing Antarctic ice core records which confirm a widespread early Holocene climate optimum during this time. This early optimum is followed by cooling temperatures to a minimum around 8000 yr BP. Most core sites studied by Masson in the Antarctic display this cool minimum. Masson also recognizes a secondary Antarctic late warm optimum between 6,000 and 3,000 yr BP.
Compared to the Arctic, the Antarctic shows a much-abbreviated early climate optimum that ends just after the Arctic climate optimum begins. While the Arctic stays warm during the Holocene climate optimum 10,000 to 6000 years BP, the Antarctic experiences a cold period from 9000 to 6000 yr BP. While the Arctic shows progressive cooling during the “Neoglacial period”, the Antarctic is experiencing a second warming trend. Therefore, the Holocene climate optimum and Neoglacial period better describe the Northern Hemisphere, not the Antarctic region. The two polar hemispheres do not warm and cool together and underlying long term trends appear to be out of phase after the Antarctic early Holocene optimum.
Polar Temperature Trends are Synchronous with Local Solar Insolation
It has long been recognized that Northern Hemisphere (NH) summer solar insolation influences reconstructed ice core temperatures (Laskar, 2004). Figure 2 shows the strong Northern Hemisphere summer insolation during the early Holocene synchronous with the Arctic temperature climate optimum. In the early Holocene, northern summer insolation reaches a maximum about 9,000 years ago. Northern insolation becomes progressively weaker during the mid-late Holocene coeval to the Arctic Neoglacial cooling trend.
In this post, Northern insolation refers to the Northern Hemisphere summer (June-August) and Southern insolation refers to the Southern Hemisphere summer (December-February). Figure 2 shows both Northern and Southern summer insolation at 65 degrees latitude which are out of phase during the Holocene. In the early Holocene, Northern summer was at perihelion when Earth is closest to the sun around 9,000 yr BP, and southern summer occurred when Earth was farthest from the sun. While Northern insolation progressively declines during most of the Holocene, Southern insolation progressively increases.
Today, northern, and southern summers are reversed from the Early Holocene. Presently, the southern summer occurs near perihelion when Earth is closest to the sun and northern summer occurs when Earth is farthest from the sun. In the future, northern insolation will continue to decline, and southern insolation which is currently strong will begin to decline.
How do Antarctic temperature trends relate to solar insolation? Masson, 2000, states that the early Antarctic climate optimum occurs at the same time as the Northern Hemispheric summer insolation optimum around 10,000 years BP. Although correct, this appears to be the only time Antarctic temperature trends display any resemblance to Northern insolation as shown in Figure 2. When Northern insolation is at an optimum around 9,000 yr BP, Antarctic temperatures are cooling towards a minimum. When Northern insolation is declining during the mid-late Holocene, Antarctic temperatures are warming or flat after the 8,200 yr BP cold period. During most of the Holocene, warming Antarctic temperature trends seems to be more aligned with increasing Southern insolation.
Holocene polar temperature trends appear to be largely synchronous and in the same direction as their local summer solar insolation. For most of the Holocene, Antarctic and Arctic temperature trends appear out of phase with each other just as Northern and Southern summer insolation are out of phase. The role of local insolation may be a strong influence on the underlying millennium-scale polar temperature trends in the polar regions.
CO2 is Synchronous with Antarctic Temperature Trends
Antarctic ice core data are routinely used as proxies for past CO2 concentrations. Antarctic CO2 data is the key dataset for paleoclimate CO2 trends during interglacial and glacial periods for the Southern Hemisphere. Surprisingly, Antarctic CO2 data is frequently used in Northern Hemisphere studies as well as compared to instrumental CO2 global trends (Ahn and Brooks, 2013, Kohler, 2011, NOAA, 2020).
Many technical articles and research from the mid-1990’s reached the hypothesis that CO2 gas in Greenland ice core bubbles were enriched by acid-carbonate chemical reactions and therefore, are unreliable (Anklin, 1995, Barnola, 1995). This theory was put forward because CO2 measurements from Greenland ice cores are more variable and generally 20-30 ppm higher than Antarctic CO2 measurements. As a result, Greenland CO2 datasets are not used in scientific studies to understand the Northern and Southern hemisphere’s interactions with and sensitivity to greenhouse gases under various climatic conditions. For a more detailed discussion on CO2 from Arctic Greenland cores, refer to my previous post here.
Figure 3 shows CO2 data plotted with Antarctic and Arctic temperature anomalies for the Holocene. CO2 tends to be synchronous with Antarctic temperatures and out of phase with Arctic temperatures. In the early Holocene, CO2 reached 270 ppm around 11,500 yr BP. CO2, then gradually decreased to a minimum of 255 ppm around 8,000 yr BP. During most of the Holocene since 8,000 yr BP, CO2 has been increasing. This increase in CO2 parallels the increase in Antarctic temperature trends and is contrary to Arctic temperature trends which decreased during this time.
It is difficult to compare the elevated CO2 records from the present to the past since CO2 data from the Northern Hemisphere during the Holocene is not publicly available. The scant Greenland CO2 data that is publicly available shows CO2 is generally 20-30 ppm higher than Antarctic CO2 and as high as 375 ppm in the Holocene (Neftel, 1982 and Barnola, 1995). Even today, Barrow and South Pole observatories have seasonal amplitude differences resulting in CO2 being 12-15 ppm higher at Barrow than in the South Pole during northern winter months almost 60% of the year (NOAA, 2020).
Holocene Polar Correlations
Holocene polar temperature anomalies over the past 10,000 years are compared to Northern insolation, Southern insolation and CO2 using Pearson’s correlation shown in Figure 4.
The Arctic and Antarctic temperature underlying millennium trends have a negative correlation confirming they are mostly out of phase. A strong positive correlation occurs between Arctic temperature anomaly trends and Northern insolation as expected. And the Arctic temperature trends shows a strong negative correlation with Southern insolation, no surprise there. Arctic temperature trends also show a strong negative correlation with CO2.
Antarctic temperature trends show a positive correlation with Southern Hemispheric insolation as well as with CO2 trends. These correlations are all strong, above 0.74. CO2 shows a surprisingly strong correlation with Southern insolation of 0.92. Interestingly, the Holocene Antarctic temperature anomaly trends show a strong negative correlation with Northern insolation.
Antarctic temperature proxy data is key to understanding paleoclimate trends and climatic conditions. The Southern Hemisphere is vastly under-represented in proxy data compared to the Northern Hemisphere for the Holocene and contains only about 10-15% of the proxy records. As seen in these polar comparisons, the Southern extratropics behave very differently than the Northern Hemisphere.
In conclusion, the often-overlooked Antarctic dances to a different beat than the Arctic. Antarctic and Arctic underlying temperature trends are mostly opposite in phase during the Holocene. Holocene polar temperatures trends are largely synchronous and in the same direction as their local summer solar insolation over the past 10,000 years suggesting local insolation influences the secular temperature trend of the polar regions.
The Holocene CO2 trends measured from Antarctic ice cores are coeval with Antarctic temperature trends and out of phase with Arctic temperature trends. Despite being routinely used in climate research, Antarctic CO2 is probably not representative of global and/or Arctic CO2 trends.
Acknowledgements: Special thanks to Donald Ince and Andy May for reviewing and editing this article.
References Cited:
Ahn, J, E. Brook, C. Buizert, Response of atmospheric CO2 to the abrupt cooling event 8200 years ago, Geophysical Research Letters/Volume 41, Issue 2, 2013. https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2013GL058177.
Anklin, M., J.M. Barnola, J. Schwander, B. Stauffer, and D. Raynaud, Processes affecting the CO2 concentration measured in Greenland ice, Tellus, Ser. B, 47, 461-470, 1995. https://onlinelibrary.wiley.com/doi/pdf/10.1034/j.1600-0889.47.issue4.6.x
Barnola, J.-M., M. Anklin, l Porcheron, D. Raynaud, l Schwander, and B. Stauffer, CO2 evolution during the last millennium as recorded by Antarctic and Greenland ice, Tellus, 47B, 264-272, 1995. https://onlinelibrary.wiley.com/doi/abs/10.1034/j.1600-0889.47.issue1.22.x
Kohler, P. G. Knorr, D. Buron, A. Lourantou, J. Chappellaz, Abrupt rise in atmospheric CO2 at the onset of the Bolling/Allerod: in-situ ice core data versus true atmospheric signals. Clim. Past, 7, 473-486, 2011. https://www.clim-past.net/7/473/2011/cp-7-473-2011.pdf
Masson, V., Vimeux, F., Jouzel, J., Morgan, V., Delmotte, M., Ciais, P., Hammer, C., Johnsen, S., Lipenkov, V. Y., Mosley- Thompson, E., Petit, J.-R., Steig, E., Stievenard, M., and Vaik- mae, R.: Holocene climate variability in Antarctica based on 11 ice cores isotopic records, Quaternary Res., 54, 348–358, 2000. https://is.muni.cz/el/1431/jaro2015/Bi8300/39087998/Masson_etal2000_climate_Antarctica_ice-core.pdf
Neftel, A, H Oeschger, J. Schwander, B. Stauffer, and R. Zumbrunn, Ice core sample measurements give atmospheric CO2 content during the past 40,000 years. Physics Institute, University of Bern. Nature Vol. 295, 1982. https://www.researchgate.net/publication/230889363_Ice_core_sample_measurements_give_atmospheric_CO2_content_during_the_past_40000_yr.
NOAA, Global Monitoring Laboratory, 2020. Visualization comparing instrumental CO2 data to past Antarctic ice core CO2 data. https://www.esrl.noaa.gov/gmd/ccgg/trends/history.html
NOAA, Global Monitoring Laboratory, 2020. Graph of Barrow, Mouna Loa, and South Pole CO2 data showing seasonal and global trends. https://www.esrl.noaa.gov/gmd/ccgg/trends/gl_trend.html
Zhengyu Liu, Jiang Zhu, Yair Rosenthal, Xu Zhang, Bette L. Otto-Bliesner, Axel Timmermann, Robin S. Smith, Gerrit Lohmann, Weipeng Zheng, OliverElison Timm. The Holocene temperature conundrum. Proceedings of the National Academy of Sciences Aug 2014, 111 (34) E3501-E3505; DOI:10.1073/pnas.1407229111, https://www.pnas.org/content/111/34/E3501
Datasets:
Arctic Agassiz-Renland temperature proxy by Vinther, 2009. ftp://ftp.ncdc.noaa.gov/pub/data/paleo/icecore/greenland/vinther2009greenland.txt
Dome C temperature proxy by Jouzel, 2001. https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/epica_domec/edc96-iso-45kyr.txt
Solar Insolation by Laskar, J., 2004. http://vo.imcce.fr/insola/earth/online/earth/online/index.php.
Dome C CO2 data by Bereiter, 2016. https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/antarctica2015CO2.xls
Thanks Renee for this excellent and important article!
This post makes the important observation that global CO2 atmospheric concentration up till the industrial age has been dominated by SH and Antarctic temperatures. Figure 3 makes this clear.
This provides further evidence that the primary source of CO2 atmospheric changes is thermal equilibrium between CO2 in the ocean and atmosphere according to Henry’s law of gas solubility and temperature. There is more water in the SH than the NH. Therefore as figure 3 above shows, atmospheric CO2 follows the temperature of the SH more than that of the NH. A lot more.
This fact is very important as it exposes a trick used by Skakun and other authors in arguing that temperature change at Holocene inception, 15-10,000 years ago, followed and thus was driven by CO2. This sleight of hand employed the difference between NH and SH in temperature change at Holocene inception, together with some clever data shuffling. In the NH there was a “false start” to the Holocene, with rapid warming 14,500 years ago in the Bolling Allerod excursion followed by a fall to cooler temperature in the North Atlantic during the 1000-year Younger Dryas (YD). After the YD Holocene warming resumed in the NH while the SH has been steadily warming since 22kya.
During the YD global atmospheric CO2 continued to rise, because the SH oceans were still warming. The SH was not much affected by the YD. In general the effect of the YD was to shift forward in time the NH start of the Holocene. What Shakun and co-perpetarators did was define the onset of the Holocene by a large number of (largely biological) proxies of temperature biased toward the NH, while comparing this to the CO2 concentration that – as we have already seen – is driven mostly by SH ocean temperature. The result is the SH-following CO2 increase slightly preceding NH-biased temperature increase and a suprious (but very influential) conclusion being drawn that somehow Holocene warming from the last glacial maximum was being driven by CO2 increases (coming from God knows where).
http://geoscience.wisc.edu/geoscience/wp-content/uploads/2010/07/Shakun_Carlson_QSR_2010.pdf
It is notable that Shakun’s paper does show the Southern Ocean’s (Antarctic) temperatures as well as rising CO2 – as Renee shows in figure 3 above. But Shakun et al put the two in different figures – fig 1 and fig 7, far apart in the paper, and no comment is made as to their similarity.
It is very important to understand that global CO2 concentration (excluding human influence) is dominated by the Southern Ocean and SH. This combined with understanding the inter-hemispheric seesawing of temperatures at Holocene inception, shows that changes in ocean water temperature precede and are causative of atmospheric CO2 rise, not the other way around.
Phil,
Yes, Shakun’s paper was very misleading. It’s also very disappointing that CO2 measurements from Antarctic ice cores are the only paleo CO2 dataset we have. I believe it is not completely representative of global CO2. Antarctic CO2 conditions are dominated by the Southern ocean as you point out and oceanic process are a longer-term underlying driver of climatic conditions.
I wish scientists would have continued to gather CO2 from Greenland ice cores even with all its warts. The scant Greenland CO2 available shows more variability and may be suggesting both oceanic as well as shorter-term terrestrial CO2 fluctuations. It’s a missing piece of the CO2 puzzle that would help explain or at least put into better context the present day centennial increase in CO2.
Renee
A lot of the original work done in Greenland was by scientists with the US Army Cold Regions Research and Engineering Laboratory (formerly SIPRE), in Hanover, New Hampshire. There have been a lot of changes wrought in the staffing and mission since I was stationed there in 1966 & 1967. I wouldn’t be surprised to discover that there are a lot of reports archived in the library that never made it into the general literature. You might want to consider soliciting the lab to see if you might be allowed to have access to unpublished reports.
Clyde,
Thanks for the contact information. I will certainly look them up.
Renee
The lab is (or at least was) unique in that it had a number of cold rooms where cores could be worked on without melting. They also archived retrieved cores there. However, after more than 50 years, I’d be concerned about gases diffusing out of the ice at low pressures. So, I don’t know whether or not they could offer physical resources to be analyzed with modern instrumentation.
Shortly before mustering out of the Army, I considered an opportunity to go to Antarctica for a drilling program that was being planned. However, there was a buildup going on in Vietnam, and knowing how the military worked, I was concerned that if I extended my tour I might end up in Vietnam instead of Antarctica. Besides, when I came back I probably wouldn’t have had a wife any longer. The bottom line is that CRREL might also have had some Antarctic cores in storage. If you are in a position to do some research, it might be worthwhile to try to determine what, if anything, remains at the lab.
Clyde,
What an interesting background. Yeah, you are right about cores being too old to be resampled for gas analysis. But I’d take any old reports or CO2 data not published yet.
I did email Ed Brooks at OSU several months ago and sent him my Greenland CO2 article. I asked him for any Greenland CO2 data he was aware of. No response.
I’d consider sponsoring or donating to a university research project that would compile and re-examine Greenland ice core CO2 data. Perhaps it would lead to additional ice core data gathering directly targeting CO2 investigation.
Renee
Do you think that leaf stomatal data is of value as a proxy for CO2?
Phil,
There is some value, of course, to more data. The biggest downside about stomatal data is it tends to exhibit localized CO2 influences. But that can also be said about tree ring data, which is extensively used as Northern Hemisphere climate temperature proxy data.
If I had a choice, I would extensively re-sample the Greenland ice cores for CO2 analyses. And secondly, drill a new Greenland ice core and use the best technology available to preserve and sample for CO2 data.
Beware of crazy climatologists rewriting history, such as the bogus Minoan Warm Period. A pair of super solar minima from 1360 BC and 1250 BC drove the decline and demise of several civilisations including the Minoans. And that was super warm in Greenland because of a negative NAO/AO regime. The centennial scale noise in GISP2 is the inverse of solar variability, the coldest periods were the warmest in the mid latitudes. During the 8.2kyr event there were expansions of village settlements in Serbia, the Indus, and in England with wheat growing and the earliest known boatyard. 2700-2500 BC saw the onset of city building worldwide, that’s the real Minoan warm period, that’s when they and many others flourished from. That’s two of the three coldest periods in GISP2 during the Holocene. The warm spike in GISP2 from around 1000 AD was the Oort solar minimum, but one should ask then why the following centennial minima in Richard Alley’s series do not show as warmer spikes. It looks rather fishy to me. It’s all too easy to get the polar seesaw upside down in relation to solar variability with the wrong idea about GISP2.
How about a new hypothesis: the co2 levels in the ice cores are a result of a fractional distillation process which fractionated the co2 concentration to a ppm equilibrium level which is temperature dependent, this would explain the close correlation between the temperature and co2 concentration for both Antarctic and Greenland ice cores? This would explain the lag of co2 to temperature and the apparent rise in co2 concentration in recent decades. The evidence from both hemisphere ice cores supports this although the mechanism is elusive although Jawarovski (sorry about the spelling) hints at something like this happening and other research shows that other trace gases fractionate in the ice cores.
Renee I enjoyed your analysis, but I think solar activity has more influence over time than orbital. Different regions respond at slightly different levels of solar energy and have different lags due to basin size, land locations, and ocean currents:
The 1935-2004 solar modern maximum profoundly affected the ocean, sea ice, Greenland, and CO2.
Bob,
Nice montage. I agree there are different lags in different geographical regions. Did you do any analysis comparing solar activity to the Southern Hemisphere or Antarctic temperatures over the past thousands of years?
I’ll defer to Leif on this one. His comment above “Solar insolation changes a lot and has different effect in the two polar regions. ….the changes in insolation completely dominates changes in solar activity”.
Thanks, Renee. This is as much for Leif as for you.
Did you do any analysis comparing solar activity to the Southern Hemisphere or Antarctic temperatures over the past thousands of years?
No but I just did and added it to the list and Fig. 4b. Holocene EPICA cools SN<90.
The answer is Antarctica responds to the sun's activity in the same range as elsewhere.
I updated the scale on Fig. 4 by setting the scale average to that of the time series to the zero line of the right-side integrated normalized function scale, SOP for these type of plots.
Ocean phases respond inversely to variations in the solar wind, low solar means increased El Nino conditions and a warm AMO.
https://www.sciencedirect.com/science/article/abs/pii/S1364682616300360
“The 1935-2004 solar modern maximum profoundly affected the ocean, sea ice, Greenland, and CO2.”
But the AMO and Greenland is always warmer during centennial solar minima. While during the strongest solar wind conditions of the space age, the AMO was at its coldest. The had to be weakening of the solar wind from 1925 for the AMO to warm, irrespective of what sunspot numbers were doing.
There had to be…etc
The AMO responded to the Modern Maximum similarly as well, cooling SN<89.3
That's my last revision of this, the final link I'll use in the future.
The solar output and solar wind are definitely connected, but the solar output is directly controlling the long-term climate warming/cooling, not the solar wind.
Bob Weber:
You state “the solar output and the solar wind are definitely connected, but the solar output is directly controlling the long-term climate warming/cooling, not the solar wind”
This is not correct.
I have done an analysis of the Central England Temperatures Instrumental data set, which spans the years 1659-present, and find no evidence of any solar variability affecting the climate.
What IS affecting the climate is varying amounts of SO2 aerosols in the atmosphere, primarily from volcanic eruptions.
https://www.Osf.io//b2vxp/
… and find no evidence of any solar variability affecting the climate.
Burl you made me make another revision! just to show you I am correct 😉
The CET (Fig. 3c) cools @ur momisugly SN<90.8, making 10 indices on my list, and there are more climate indices in the same sunspot range not on those charts that could fill many pages.
SO2 volcanic aerosols are short-term and easily over-powered by solar forcing
Bob Weber:
Regarding your post of May 30, 8:05 pm, where you attempted to show that you were correct.
You need to download and study the link that I provided.
You will see that all of my comments are fully supported by the data, and you need to wrap your mind around them, as uncomfortable as that may be.
Burl wrote:
“I have done an analysis of the Central England Temperatures Instrumental data set, which spans the years 1659-present, and find no evidence of any solar variability affecting the climate.”
Well you cannot be looking in the right place as much of the variability in CET is solar driven at the scale of weather, and modulated by the AMO which is also solar driven
“What IS affecting the climate is varying amounts of SO2 aerosols in the atmosphere, primarily from volcanic eruptions.”
Large eruptions typically follow much colder N Hem winters, and slightly warm 1-2 following winters through a positive influence on the NAO, and slightly cool 1-2 subsequent summers. So weather effects volcanoes and then the eruptions effect the weather, but they don’t cause colder CET winters.
Ulrich Lyons:
You need to view the link which I provided.
Central England temperature excursions precisely match the temperature effects of volcanic eruptions, increasing when there are no eruptions, and decreasing when there is a VEi4 or larger eruption.
Bob wrote:
“The AMO responded to the Modern Maximum similarly as well, cooling SN<89.3"
Sunspot has little to do with it, AMO variability is an inverse response to the solar wind strength.
Ulric,
Sunspots, the long-term TSI proxy, TSI, and the IMF ie solar wind co-vary with the sun’s magnetic field, and inversely with cosmic rays.
Solar wind negative Bz events are irregular and short-lived, w/o effect on tropics, where AMO heat derives – same reason Svensmark’s cosmic ray cloud theory is bunk – no effect on the tropics where warming/cooling is TSI/insolation driven.
The AMO as a solar accumulation function has it’s own long-term tempo due basin size.
Bob writes:
“Sunspots, the long-term TSI proxy, TSI, and the IMF ie solar wind co-vary with the sun’s magnetic field, and inversely with cosmic rays.”
Not so, there were major lows in the solar wind at sunspot maximums in 1969 and 1979-80, after which the major lows shifted to about a year past sunspot minimum in 1997 and 2009. Which is why the AMO anomalies have shifted from being in phase with sunspot cycles during the cold AMO phase, to anti-phase with sunspot cycles during the warm AMO phase.
The reason why Svensmark’s ideas are wrong is because weaker solar wind drives warmer ocean phases which then reduce low cloud cover.
Weaker solar wind causes negative NAO/AO states which are directly associated with slower trade winds, that’s why there is an increase in El Nino conditions during centennial solar minima. Negative NAO/AO states directly drive warm AMO anomalies via ocean gyres in the North Atlantic effecting the overturning rates. And then there is a ~8 month lagged positive feedback from El Nino episodes driving major AMO warm pulses.
EPICA CO2 lags temperature by 400-600yr with a Millenial Sensitivity of 7.8ppm/C @ur momisugly R=.9, R^2=.8:
The annual perihelion insolation pulse peaks in January over the southern ocean, ultimately driving CO2:
The sun’s early year warming of Nino34 then first affects Antarctic sea ice, then Arctic sea ice:
The main reason the Antarctic CO2 isn’t the best overall is the larger expanse of ice-free cold waters ringing the Antarctic sea ice and shores that continually sink more CO2 than the Arctic cold waters which don’t sink anything in comparison when covered with ice.
Bob,
Thanks for confirming that Antarctic CO2 isn’t the best overall measurement to use. Unfortunately, it’s the only CO2 data available before 1960 instrumental data and is frequently used as a past comparison to global present day CO2.
Renee I am walking back my comment on that a bit, as on the flipside of that is Antarctica CO2 measurements are likely stable because the conditions there change so slowly, and since Law Dome CO2 segues so well into Mauna Loa CO2; however Law Dome CO2 data is also likely attenuated and smoothed too much going further back in time.
As evidenced by the seasonal variation in CO2 draw-down and replenishment, which shows minimal time lag, I’d say that the time lag you cite is an argument for the oceans being the primary source of atmospheric CO2, given the known slow, deep currents with a recycle time of hundreds of years.
Could local solar insolation be the missing link?
“the mechanisms that are responsible for generating the anti-correlation of the northern and southern hemisphere warrants further investigation. This phenomenon requires substantial changes in net hemispheric air-sea heat exchanges”
https://www.nature.com/articles/s41467-020-15754-3