1. decreasing the output of energy by the sun
• circulation rates within sun
• availability of fuel for nuclear fusion
2. intercepting the energy between the sun and earth
• modification of ionosphere of sun
• modification of interplanetary field
  
  

1. SOLAR EVOLUTION PARADOX: 4.5 billion years ago sun was ca. 8% smaller and ca. 3 % less luminous so solar constant was ca. 25 % less. As sun converts Hydrogen to Helium, the luminosity will continue to increase over next 4 by (Walter & Barry, 1991)

2. GLACIAL EPISODES (250 my cycle) 1947 Umbgrove noted: Glacial ages occur on ca. 200 my cycle Dilke and Gough (1972) propose that mixing in the sun's core produces periodic (ca. 109 yr) fluctuations in solar luminosity STIENER - GRILLMAIR (1973) suggest that 250 my cycle in solar variability caused by the sun's orbit around the galaxy. 7 of the 12 periods during the last 4.5 by when sun farthest from center of galaxy, have "documented" glaciations 5 "missing" glacial episodes explained of lack of suitable geographical distribution of continents mechanisms: when the earth is farthest "out" lower gravity force = cooler sun due to slower circulation within sun slower orbital velocity = sun accretes less Hydrogen, less fuel Interstellar Dust?

3. SUNSPOTS AND SOLAR ACTIVITY

• European telescopic observations of sun began 1610
• Chinese observations 1000 years earlier (through loess clouds)
  

R = k(10g+s) R is the Wolf sunspot number g is the number of sunspot groups on the solar disk s is the total number of individual spots in all groups k is a variable scaling factor (usually <1)

• ¹⁰Be: polar ice cores only
• ¹⁴C: Little Ice Age sunspot minima correlate with Positive ¹⁴C anomalies
  • ¹⁴C/¹²C ratio is high when sunspot number is low
  • Dating of tree rings demonstrates a pattern of deviations
    Δ ¹⁴C ‰: difference between measured ¹⁴C and amount that would result in 1:1 ¹⁴C vs. calendar age:

A. Earth's carbon reservoir: doubling of biosphere = 0.4 - 1.0% lower ¹⁴C
B. Changes in Earth's geomagnetic field

• Unstable ¹⁴C isotopes are produced by the ¹⁴N(n,p)¹⁴C reaction in the upper atmosphere, resulting from cosmic ray bombardment.
  
• Strength of Earth's magnetic field shows inverse relationship to -¹⁴C, archeomagnetic study (Merril and McElhinny 1983)
A strong geomagnetic field deflects cosmic rays and, therefore, reduces the rate of ¹⁴C production.


C. Changes in solar activity (A.E. Douglas!)


An active sun results in a strong solar wind; deflects cosmic rays and decrease ¹⁴C production: positive ¹⁴C anomaly = cold climate (see Wang et al., 1996)



Cosmogenic Isotope Anomalies

Historic

Science NASA (cycle 22)

Satellite observations indicate that during 11-yr cycle sunspot minimum, solar irradiance is lower (0.1%), interplanetary magnetic field weaker (Radick,1990; Wang et al., 1996; Willson, & Hudson 1988; Willson, et al. 1985) Link

50% to 15% annual variability explained: SE USA colder during sunspot maxima IF QBO blowing from west - ENSO confounding (van Loon and Labitzke, 1988)

Cosmic ray bombardment produces ¹⁰Be, record is similar to ¹⁴C, confirms solar modulation (McHargue and Damon, 1991; Beer et al., 1988)

Lengths of 11 yr (Hale) cycles correlates with global temperature (Friis-Christensen and Lassen, 1991)

Positive ¹⁴C anomalies are called "Minima" due to the ¹⁴C - sunspot correlation (Eddy, 1977) older minima are named for, "the general historical period in which the apparent anomaly falls. (Eddy, 1977, p 183)."

Little Ice Age

Solar irradiance (Earth temperature) lower during long-term (200, 80 yr) sunspot minima and magnetic field weaker so more ¹⁴C produced

Medieval Warm Period

Wet MWP in the Southwest (Davis, 1994)

Dry MWP Europe

Dry MWP in the Sierra Nevada, high lake-levels during positive 14C anomalies
SUNSPOT MINIMA		PROXY RECORD		LAKE HIGH STAND
Name	Name	Age 14C	Age 10Be	Jura Alps, Fr	Mono L., CA
Dalton		1825 AD	1825 AD
Maunder	Maunder	1710 AD	1710 AD		Clover Ranch
Sporer	Sporer	1550 AD	1510 AD		Danberg Beach
			AD 1450		10-ml road lowstand
Wolf	Yuan	1330 AD	1290 AD		Rush Delta
			AD 1350		Simnis Ranch lowstand
Medieval	Song	1050 AD	1010 AD		Post Office
			AD 1100		Lee Vining lowstand
Roman IV	Medieval	690 AD	670 AD	P.Maclu 2
Roman III	Wei	450 AD	430 AD
			AD 300		Marina Lowstand
Roman II		270 AD	210 AD
Roman I		90 AD	110 AD	P.Maclu 1
Greek		330 BC	290 BC	Bourget
Homeric		750 BC	770 BC	Bourget
Egyptian		1370 BC	1370 BC	Pluvis
Silver Lake		1870 BC	1910 BC		Dechambeau R.
Noachan		2850 BC	2870 BC
Sumerian II		3290 BC	3490 BC	Chalain
Sumerian I		3570 BC	3690 BC
Jerico		5190 BC	5030 BC	Cern
Sahelan		5950 BC	6230 BC
Eddy, 1977; Davis, 1992	Youji, 1983			Magny, 1993	Stine, 1990; Stine, 1994

Correlation of solar luminosity and temperature over the last 1000 years

Modeling Crowley, 2000. Haigh, 1996. Kromer et al., 2004.

SUNSPOT "MINIMA" - ¹⁴C ANOMALIES

Damon	AD 1880-1930	Global Temp 0.5 oC lower (Jones, 1988)	L I A 5
Dalton	AD 1795-1825	"Year Without Summer" 1813
Maunder	AD 1650-1710	Little Ice Age, Global Temp 1-2 oC lower
Sporer	AD 1420-1540	Second Little Ice Age event
Wolf	AD 1280-1340	The Great Drought
Greek	330 BC
Homeric	750 BC
Egyptian	1370 BC
Silver Lake	1870 BC
Noachan	2850 BC
The Greek and Homeric events together have been called the "Hallstat Period" - a precurson or the Little Ice Age. REF All names informal, those in bold are in common usage.

CYCLICITY & PREDICTABILITY

Because ¹⁴C cycles quasi periodic, Damon and Sonett (1989) predict future climate

Cycle length	Cycle name	Last positive 14C anomaly	Next "warming"
2241	Landscheidt	AD 1400 (cool)	AD 2520
512	--?--	not used	*
232	--?--	AD 1922 (cool)	AD 2038
208	Suess	AD 1898 (cool)	AD 2002
88	Gleisberg	AD 1986 (cool)	AD 2030
22	Schwabe
11	Hale
* REFERENCES TO 512 YEAR CYCLE Chapman, M.R. and Shackleton, N.J. (2000). Evidence of 550-year and 1000-year cyclicities in North Atlantic circulation patterns during the Holocene. Holocene. 2000; 10(3): 287-291. (Eglinton et al., 1992 Nature 356: 423-426. ) NW Africa ODP core had strong 590 and 550 yr cycles from Termination IV. (Pederson, 2000 GSA Bulletin 112: 147-158.) SE Utah Lake Canyon & Black Mesa 500-550 yr wet-dry cycles late Holocene, also tree rings. Sarnthein, M., van Kreveld, S., Erlenkeuser, H., Grootes, P.M., Kucera, M., Pflaumann, U., and M. Schulz. Centennial-to-millennial-scale periodicities of Holocene climate and sediment injections off the western Barents shelf, 75°N. (Boreas, in press). Schulz, M. & Paul, A. 2002: Holocene climate variability on centennial-to- millennial time scales: 1. Climate records from the North-Atlantic realm. In Wefer, G., Berger, W. H., Behre, K.-E. & Jansen, E. (eds.): Climate development and history of the North Atlantic Realm, 41-54. Springer Verlag, Berlin. (Available from first authors' web site: http://www.palmod.uni-bremen.de/~mschulz/) (Sonett & Suess, 1984 Nature 307: 141-143.) They mention a "very strong" 500 year signal in limber pine from southern CA. Stager et al., 1997. Quat Res. 47:81-89) 510 year cycle from Lake Victoria, East Africa, diatom record. My newest core from the lake also show it. (Stuiver et al., 1995 Quat. Res. 44:341-354.) Got near 530 yr cycle in GISP2 ice core, postulated solar (Stuiver & Brauzanias, 1993 Nature 338:405-408) Cited in Mayewski et al JGR 1997.......Early Holocene had ca. 512 yr cycle maybe related to marine circulation. It's also in GISP2 (von Rad et al., 1999 Quat. Res. 51: 39-53.): Arabian Sea OMZ core had significant 500 yr cycle Yu and Ito. Possible solar forcing of century-scale drought frequency in the northern Great Plains. Geology 27: 263-266. PALEOCLIMATE LISTSERV Friday, February 28, 2003 11:30 AM, Tuesday, March 04, 2003 8:31 AM, Dr. Sushma Prasad, JAY C STAGER [stagerj@paulsmiths.edu]

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