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Has the Sun’s Output Really Changed Significantly Since

the Little Ice Age?

Leif SvalgaardStanford University, CA, USA

leif@leif.orghttp://www.leif.org/research

Tromsø, Norway, May 27, 2010

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Was the Little Ice Age Global?Sun that gives all things birth Shine on everything on earth! If that's too much to demand Shine at least on this our land If even that's too much for thee Shine at any rate on me

Piet Hein (Danish Poet, 1905-1996)

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Craig Loehle: Global Temperature Reconstruction [non-tree ring].

Range ~1ºC

Little Ice Age

Medieval Warm Period

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Total Solar Irradiance, TSI Global Heat Flow dT/T = ¼ dS/S; dS/S = 1% dT = 0.25%T ~ 1ºC

When Jack Eddy Proposed a Connection Between the Maunder Minimum and the LIA it was thought that dS/S of 1% was a possible variation (Abbot)

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Measurement of TSI by spacecraft

0.1%

Annual Variation (due to variation of solar distance) is 70 times larger than solar cycle variation:

Solar activity

Several cavities

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Putting TSI variations in Perspective

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The ‘Solar Constant’

Adjusted for Variation of Distance to the Sun

BTW: What is the ‘Distance’ to the ‘Sun’? Sphere, Size, Moon, …

During the (avg.) 499 seconds of flight the distance changes…

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TSI is the combined effect of sunspot dimming and facular brightening (2x)

Faculae are areas with significant magnetic fields near sunspotsdifference

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Degradation of Active Cavity Instruments due to Harsh Space Environment

y = 1.00328899316e-0.00001268600x

1360

1361

1362

1363

1364

1365

1366

1367

0 1 2 3 4 5 6 71.003050

1.003100

1.003150

1.003200

1.003250

1.003300

1.003350

1.003400

1.003450

1.003500

2004.0

PMOD

SORCE

Ratio

Comparison PMOD and SORCE-TIM

2005.0 2006.0 2010.02009.02008.02007.0 2011.0

SOHO Keyholes

In an ideal world the ratio [or difference] between PMOD TSI (SOHO at L1) and SORCE TIM TSI (LEO) should be constant. This is not the case. The ratio PMOD/SORCE is slowly decreasing exponentially:

Sometime in 2003 the azimuth drive of the high gain antenna (on SOHO) got stuck. The operations people were able to move to a position which was ok for most of the halo orbit (±30 degrees seen from Earth). As the antenna is locked at one azimuthal angle, SOHO is turned around its solar axis by 180 deg for the East or West legs of the orbit, respectively. So in this context, the ’keyhole’ is when low emission in the antenna pattern close to extremes of the halo orbit are encountered. The different orientation of the spacecraft may have thermal effects.

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Reconstructions of TSI often use the Sunspot Number [going back 400 years]

Different series of sunspot numbers are in use, according to what fits your pet theory the best

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Early Reconstructions TSI ~ TSI0 +a·SSN + b·<SSN>11yr

Now

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Solar Magnetic Field Heliospheric Magnetic Field Geomagnetic Activity:Centennial Secular Increase ?

Lockwood et al., 1999 Aa-index and Method Wrong

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HMF from Geomagnetism

y = 1.4771x0.6444

R2 = 0.8898y = 0.4077x + 2.3957

R2 = 0.86370

2

4

6

8

10

0 2 4 6 8 10 12 14 16

IDV

HMF B as a Function of IDV09

B nT 1963-2010

0

2

4

6

8

10

1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

B nT

Year

B (IDV)

B (obs)

Heliospheric Magnetic Field Strength B (at Earth) Inferred from IDV and Observed

13 23

NowThen

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Historical Sunspot Number Records Probably Not Correct

0

10

20

30

40

50

60

70

1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

HLS Helsinki Nine Station Chain NUR Nurmijarvi

Stability of Amplitude of Diurnal Variation of East Component

nT

Year

Current System in Ionosphere Created by UV Radiation Produces Diurnal Magnetic Effect at the Surface (1722)

Morning

Afternoon

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Even the Scientists that Advocated the Large Variation of TSI are Doubting that now

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So, Reconstructions of TSI are converging towards having no ‘background’

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Solar Activity Influences the Production of Radioactive Nuclides

If we can understand the various processes involved it might be possible to reconstruct solar activity from the cosmogenic isotopes deposited in ice (10Be).

If the 14C production varies, there will be a difference between the age calculated from the assumption of constant production and the age determined by other means [e.g. tree rings]

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14C Age Differences Partly Due to Solar

Activity

200-yr running mean subtracted

Earth’s Field

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10Be-based Reconstructions of Heliospheric Magnetic Field

The ‘dips’ may be influenced by volcanic activity; Krakatoa, Tambora, Hekla. Or even by climate changes [circular argument?]

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Global Temp.

Solar Output, TSI

10Be and 14C-based reconstructions are largely in agreement

TSI, Steinhilber et al.

14C10Be

LIA

MWP

+1 W/m2 +0.05ºC

-1 W/m2 - 0.05ºC10Be

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Conclusion

• Variation in Solar Output is a Factor of Ten too Small to Account for The Little Ice Age,

• Unless the Climate is Extraordinarily Sensitive to Very Small Changes,

• But, Then the Phase (‘Line-Up of Wiggles’) is Not Right

• Way Out: Sensitivity and Phases Vary Semi-Randomly on All Time Scales.

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Why Were There No Sunspots During the Maunder Minimum?

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When the Magnetic Field of a Sunspot Falls Below 1500 G, the Spot Becomes Invisible

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The F10.7 cm Microwave Flux Also Shows that Lately Sunspots are Harder to See

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