A new paper (Moffa-Sánchez et al) reports that they looked at layers of dead plankton in ocean mud (otherwise known as foraminifera in marine sediments) and have reconstructed the temperature and salinity of a couple of spots in the North Atlantic between 818AD – 1780 with data on δ18O and the Mg/Ca ratios. One immediate thought, an aside, is that if this technique works, there is no shortage of ocean mud, surely, and perhaps we could drill and analyze more mud for solar correlations in other places. (I hear foraminifera live in the Southern Hemisphere too). Perhaps no one is looking for the connection with the sun?
Moffa-Sánchez et al find the big climate shifts (the 100-year variations) correlate with total solar irradiance (TSI). See especially that orange line black line track in the d graph below. I stress, correlations don’t mean causation and the mechanism is mere speculation. But I find the graph intruiging. There are a lot of turning points, and in pure “curve fitting” type of analysis, this is a better curve fit than the one with CO2. (Find me a turning point that matches with carbon dioxide!) I suspect we’ll be referring back to this paper, and I hanker for more TSI comparisons with other sites and regions.
Figure 2 | Proxy records from RAPiD-17-5P. a, Solar irradiance forcing reconstruction based on the cosmogenic nuclide 10Be (ref. 10; orange) and global volcanic stratospheric aerosols30 (grey) TSI, total solar irradiance. b,
Temperature and c, salinity/18Osw estimates derived from paired Mg/Ca and 18O measurements in G. inflata calcite from RAPiD-17-5P. SMOW, standard mean ocean water. d, Three-point smoothed temperature record
from RAPiD-17-5P (black) and 1TSI (ref. 10) (orange). A 12.42-year lag has been imposed on the 1TSI forcing as indicated from the highest Pearson correlation (Supplementary Notes, Supplementary Fig. 3). Shaded areas
highlight the well-known periods of solar minima. (Click to enlarge and see original unscaled graph*)
The researchers suggest that when solar activity is low the winter jet stream over the North Atlantic is more likely to get blocked. (Which means vast tongues of cold arctic air stretch far to the south, and someone somewhere, gets freaky and not-nice weather.)
Scientists studied seafloor sediments to determine how the temperature of the North Atlantic and its localised atmospheric circulation had altered. Warm surface waters flowing across the North Atlantic, an extension of the Gulf Stream, and warm westerly winds are responsible for the relatively mild climate of Europe, especially in winter. Slight changes in the transport of heat associated with these systems can lead to regional climate variability, and the study findings matched historic accounts of climate change, including the notoriously severe winters of the 16th and 18th centuries which pre-date global industrialisation. — Science Daily
Back when CO2 levels were “ideal” the climate apparently swung wildly:
The results of these analyses revealed large and abrupt temperature and salinity changes in the north-flowing warm current on time-scales of several decades to centuries. Cold ocean conditions were found to match periods of low solar energy output, corresponding to intervals of low sunspot activity observed on the surface of the sun. Using a physics-based climate model, the authors were able to test the response of the ocean to changes in the solar output and found similar results to the data.
Low solar activity happened at the same time as blocking patterns appeared over Europe in the little Ice Age:
The results agree with the early concept that the severe winters experienced in Europe during the Maunder Minimum were caused by periods of increased atmospheric blocking1 and are also consistent with SLP field reconstructions that show a high-pressure system over northwest Europe towards the end of the Spörer and during the Maunder Minimum 20. Similarly, a number of studies suggest a negative NAO state during the Maunder Minimum or other periods of low TSI (ref. 21), in agreement with increased blocking arising from the weaker westerly winds.
Has the TSI stopped correlating? There is evidence from the last 50 years that supports the connection:
Growing evidence for the linkage between solar variability and frequency of blocking in the Northeast Atlantic has also been provided by meteorological studies. Modern observations show strong solar modulation of the blocking frequency and positioning during the 11-year solar cycles for the past 50 years, impacting substantially on UK winter temperatures22,23
The HockeySchtick points out:
The new paper contradicts claims by CAGW alarmist Jennifer Francis that global warming will cause an increase of jet stream blocking events, finding instead that jet stream blocking was more common during cold periods such as the Little Ice Age.
The researchers point out that none of these natural swings will be as big and as important as man-made CO2, not that anything in their results suggests that at all, but they have to put in these caveats in order to get published.
The essential, meaningless caveat:
“Predictions suggest a prolonged period of low sun activity over the next few decades, but any associated natural temperature changes will be much smaller than those created by human carbon dioxide emissions, say researchers.”
The two ice cores are the black dots south of Greenland and Iceland in this map.
Figure 1 | Sea surface temperature map for January 2008 showing the schematic surface circulation of the North Atlantic and the core location of RAPiD-17-5P and RAPiD-35-25B (Supplementary Methods). Solid arrows indicate the warm salty waters from the tropics, namely the North Atlantic Current (NAC) and its main branches such as the Irminger Current (IC). The dashed arrows indicate the cold polar south-flowing waters such as the East Greenland Current,West Greenland Current and Labrador Current, which constitute the western branch of the subpolar gyre (SPG). Locations of RAPiD-17-5P (61 28.900 N, 19 32.160 W, 2,303m water depth) and RAPiD-35-25B (57 30.470 N, 48 43.400 W, 3,486m water depth) are marked with a black circle (adapted from UK Met O ffice Operational Sea Surface Temperature and Ice Analysis data29).
Where are all those Australian proxies?
There are hardly any long term reconstructions of Australian temperatures. There are so few, the scientific-ABC nexus got all excited over a paper by Gergis et al which essentially reconstructed the temperature of the entirety of Australasia in 1200 AD from just two tree proxies. The paper claimed Australasia had warmed by the frightening amount of nine one hundredths of a degree in the last 1000 years. Not long later it was withdrawn. We still wonder why it was published. But my point is, can we do foraminifera studies downunder? (Or corals, stalagmites, clam shells, etc). Surely we are not short of ocean mud.
ABSTRACT
There were several centennial-scale fluctuations in the climate and oceanography of the North Atlantic region over the past 1,000 years, including a period of relative cooling from about AD 1450 to 1850 known as the Little Ice Age1. These variations may be linked to changes in solar irradiance, amplified through feedbacks including the Atlantic meridional overturning circulation2. Changes in the return limb of the Atlantic meridional overturning circulation are reflected in water properties at the base of the mixed layer south of Iceland. Here we reconstruct thermocline temperature and salinity in this region from AD 818 to 1780 using paired 18O and Mg/Ca ratio measurements of foraminifer shells from a subdecadally resolved marine sediment core. The reconstructed centennial-scale variations in hydrography correlate with variability in total solar irradiance. We find a similar correlation in a simulation of climate over the past 1,000 years.We infer that the hydrographic changes probably reflect variability in the strength of the subpolar gyre associated with changes in atmospheric circulation. Specifically, in the simulation, low solar irradiance promotes the development of frequent and persistent atmospheric blocking events, in which a quasi-stationary high-pressure system in the eastern North Atlantic modifies the flow of the westerly winds.We conclude that this process could have contributed to the consecutive cold winters documented in Europe during the Little Ice Age.
REFERENCE
Paola Moffa-Sánchez, Andreas Born, Ian R. Hall, David J. R. Thornalley & Stephen Barker (2014) Solar forcing of North Atlantic surface temperature and salinity over the past millennium, Nature Geoscience, doi:10.1038/ngeo2094 [abstract]
21. Gray, L. J. et al. Solar influences on climate. Rev. Geophys. 48, RG4001 (2010).
22. Woollings, T., Lockwood, M., Masato, G., Bell, C. & Gray, L. Enhanced
signature of solar variability in eurasian winter climate. Geophys. Res. Lett. 37,
L20805 (2010).
23. Barriopedro, D., García-Herrera, R. & Huth, R. Solar modulation of Northern
Hemisphere winter blocking. J. Geophys. Res. 113, D14118 (2008)
h/t HockeySchtick and Tallbloke see also Science Daily
*The original graph is tall and skinny. It seems a waste to compress a thousand years of information so I stretched the image horizontally, but otherwise did not change it.
*Headline order flipped, thanks to Brian in comments.