Temperature in the Northern Hemisphere
From Climate Change Reconsidered, a work of the Nongovernmental International Panel on Climate Change
Evidence of the influence of the sun on Northern Hemisphere temperatures can be found in the seminar research of Bond et al. (2001), who examined ice-rafted debris found in three North Atlantic deep-sea sediment cores and cosmogenic nuclides (10Be and 14C) sequestered in the Greenland ice cap (10Be) and Northern Hemispheric tree rings (14C).
Bond et al. found that “over the last 12,000 years virtually every centennial time-scale increase in drift ice documented in our North Atlantic records was tied to a solar minimum,” and “a solar influence on climate of the magnitude and consistency implied by our evidence could not have been confined to the North Atlantic,” suggesting that the cyclical climatic effects of the variable solar inferno are experienced throughout the world. Bond et al. also observed that the oscillations in drift-ice they studied “persist across the glacial termination and well into the last glaciation, suggesting that the cycle is a pervasive feature of the climate system.”
Björck et al. (2001) assembled a wide range of lacustrine, tree-ring, ice-core, and marine records that reveal a Northern Hemispheric, and possibly global, cooling event of less than 200 years’ duration with a 50-year cooling-peak centered at approximately 10,300 years BP. According to the authors, the onset of the cooling event broadly coincided with rising 10Be fluxes, which are indicative of either decreased solar or geomagnetic forcing; and since the authors note that “no large magnetic field variation that could have caused this event has been found,” they postulate that “the 10Be maximum was caused by distinctly reduced solar forcing.” They also note that the onset of the Younger Dryas is coeval with a rise in 10Be flux, as is the Preboreal climatic oscillation.
Pang and Yau (2002) assembled and analyzed a vast amount of data pertaining to phenomena that have been reliably linked to variations in solar activity, including frequencies of sunspot and aurora sightings, the abundance of carbon-14 in the rings of long-lived trees, and the amount of beryllium-10 in the annual ice layers of polar ice cores. In the case of sunspot sightings, the authors used a catalogue of 235 Chinese, Korean, and Japanese records compiled by Yau (1988), a catalogue of 270 Chinese records compiled by Zhuang and Wang (1988), and a time chart of 139 records developed by Clark and Stephenson (1979), as well as a number of later catalogues that made the overall record more complete.
Over the past 1,800 years, the authors identified “some nine cycles of solar brightness change,” which include the well-known Oort, Wolf, Sporer, Maunder, and Dalton Minima. With respect to the Maunder Minimum—which occurred between 1645 and 1715 and is widely acknowledged to have been responsible for some of the coldest weather of the Little Ice Age—they report that the temperatures of that period “were about one-half of a degree Celsius lower than the mean for the 1970s, consistent with the decrease in the decadal average solar irradiance.” Then, from 1795 to 1825 came the Dalton Minimum, along with another dip in Northern Hemispheric temperatures. Since that time, however, the authors say “the sun has gradually brightened” and “we are now in the Modern Maximum,” which is likely responsible for the warmth of the Current Warm Period.
The authors say that although the long-term variations in solar brightness they identified “account for less than 1% of the total irradiance, there is clear evidence that they affect the Earth’s climate.” Pang and Yau’s dual plot of total solar irradiance and Northern Hemispheric temperature from 1620 to the present (their Fig. 1c) indicates that the former parameter (when appropriately scaled, but without reference to any specific climate-change mechanism) can account for essentially all of the net change experienced by the latter parameter up to about 1980. After that time, however, the IPCC surface air temperature record rises dramatically, although radiosonde and satellite temperature histories largely match what would be predicted from the solar irradiance record. These facts could be interpreted as new evidence of the corruptness of the IPCC temperature history.
In a separate study, Rohling et al. (2003) “narrow down” temporal constraints on the millennial-scale variability of climate evident in ice-core δ18O records by “determining statistically significant anomalies in the major ion series of the GISP2 ice core,” after which they conduct “a process-oriented synthesis of proxy records from the Northern Hemisphere.” With respect to the temporal relationships among various millennial-scale oscillations in Northern Hemispheric proxy climate records, the authors conclude that a “compelling case” can be made for their being virtually in-phase, based on (1) “the high degree of similarity in event sequences and structures over a very wide spatial domain,” and (2) “the fact that our process-oriented synthesis highlights a consistent common theme of relative dominance shifts between winter-type and summer-type conditions, ranging all the way across the Northern Hemisphere from polar into monsoonal latitudes.” These findings, they additionally note, “corroborate the in-phase relationship between climate variabilities in the high northern latitudes and the tropics suggested in Blunier et al. (1998) and Brook et al. (1999).”
Rohling et al. further report that although individual cycles of the persistent climatic oscillation “appear to have different intensities and durations, a mean periodicity appears around ~1500 years (Mayewski et al., 1997; Van Kreveld et al., 2000; Alley et al., 2001).” They further report that “this cycle seems independent from the global glaciation state (Mayewski et al., 1997; Bond et al., 1999),” and that “10Be and delta 14C records may imply a link with solar variability (Mayewski et al., 1997; Bond et al., 2001).”
Lastly, we come to the study of Usoskin et al. (2003), who note that “sunspots lie at the heart of solar active regions and trace the emergence of large-scale magnetic flux, which is responsible for the various phenomena of solar activity” that may influence earth’s climate. They say “the sunspot number (SN) series represents the longest running direct record of solar activity, with reliable observations starting in 1610, soon after the invention of the telescope.” To compare SN data with the millennial-scale temperature reconstruction of Mann et al. (1999), the directly measured SN record must be extended back in time at least another 600 years, which Usoskin et al. did using records of 10Be cosmonuclide concentration derived from polar ice cores dating back to AD 850. In accomplishing this task, they employed detailed physical models that they say were “developed for each individual link in the chain connecting the SN with the cosmogenic isotopes,” and they combined these models in such a way that “the output of one model [became] the input for the next step.”
The reconstructed SN history of the past millennium looks very much like the infamous “hockey stick” temperature history of Mann et al. (1999). It slowly declines over the entire time period—with numerous modest oscillations associated with well-known solar maxima and minima—until the end of the Little Ice Age, whereupon it rises dramatically. Usoskin et al. report, for example, that “while the average value of the reconstructed SN between 850 and 1900 is about 30, it reaches values of 60 since 1900 and 76 since 1944.” In addition, they report that “the largest 100-year average of the reconstructed SN prior to 1900 is 44, which occurs in 1140-1240, i.e., during the medieval maximum,” but they note that “even this is significantly less than the level reached in the last century.” Hence, they readily and correctly conclude, on the basis of their work, that “the high level of solar activity since the 1940s is unique since the year 850.”
The studies reported in this section show that the temperature record of the Northern Hemisphere supports the theory that solar cycles strongly influence temperatures.
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