Long term monitoring of Total Solar Irradiance: Results and

Long term monitoring of Total Solar Irradiance: Results and Challenges Werner Schmutz, PMOD/WRC, Switzerland Wien, COPUOS, February 9, 2012

Overview • Introduction:

The role of solar forcing is not yet understood

• Results:

− 30 years of TSI space observations − Measurement of the absolute value of TSI

• Challenge #1:

− Construct a TSI composite over 30 years

• Challenge #2:

− Maintain TSI monitoring in the future !

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Comparison irradiance forcing with ice ages

Illustration from Wikipedia 9.2.2012

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Climate anomalies Maunder

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Temperature reconstruction Uncertainty is large !

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Temperature reconstructions

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IPCC radiative forcing

LOSU Level of Scientific Understanding

! 9.2.2012

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Results …

Since 1979 Total Solar Irradiance is measured from space

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TSI from space experiments

TIM/SORCE 2003 -

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TSI from space experiments

4.5 W/m2 difference in the absolute level of TIM/SORCE versus all other experiments

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PICARD – a French Micro-satellite PREMOS – Swiss radiometer on PICARD PREMOS – SOVAP – SODISM

Filter Radiometers

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Total Solar Irradiance

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Irradiance calibration PREMOS A is the first and so far only radiometer in space with a SI-traceable irradiance calibration in vacuum Traceable to the irradiance calibration facility at LASP in Boulder (TRF) •PICARD was launched June 15, 2010 •PREMOS first light was July 27th, 2010 9.2.2012

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The absolute value of the solar constant

ACRIM scattering correction determined at TRF (with ACRIM witness instrument)

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... and the new PREMOS data

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The Solar Constant PREMOS/PICARD The Solar Constant is 1361 W/m2 in agreement to the value from TIM/SORCE and (re-characterized) ACRIM3, which both were not SI-traceable calibrated PICARD: French Micro-Satellite

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There are three TSI composites

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TSI-composites normalized

PMOD, ACRIM


0.2 W/m2 / 10-years DIARAD

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normalized 2004-2005

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Is there a long-term trend?

Fröhlich 2009, A&AL 501, L27-L30

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Could we detect a trend with a composite?

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Requirements for a TSI monitoring „Any plan to rely on an unbroken chain of measurements is broken“ o o

Not only because of a potential gap; But mainly because of the continuously increasing uncertainty. Accurate absolute measurements are required !

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Presence … Presently, 4 operational space experiments observing TSI: - VIRGO (launched 1995) - ACRIM III (launched 2000) - TIM (launched 2003) - PREMOS (launched 2010)

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… and future Presently, 4 operational space experiments observing TSI: - VIRGO (launched 1995) - ACRIM III (launched 2000) Several new missions with TSI - TIM (launched 2003) instruments are in the planning … - PREMOS (launched 2010) … but no new mission is really approved so far !!

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...x ? ...x ? ...x ?

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Thank you for your attention

PREMOS

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PICARD

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