The Total Solar Irradiance Record and Its Continuity
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GC42A Dec. 13, 2007 RICHARD C. WILLSON - COLUMBIA UNIVERSITY 1 The Total Solar Irradiance Record and Its Continuity ACRIM SCIENCE TEAM Dr. Richard C. Willson Principal Investigator Columbia University [email protected] ACRIM Active Cavity Radiometer Irradiance Monitor Experiments ACRIMSAT/ACRIM3 ACRIM INSTRUMENT TEAM Roger S. Helizon ACRIMSAT Project Mgr. Jet Propulsion Laboratory [email protected]
Transcript of The Total Solar Irradiance Record and Its Continuity
GC42A Dec. 13, 2007
RICHARD C. WILLSON -COLUMBIA UNIVERSITY 1
The Total Solar Irradiance Record and Its Continuity
ACRIM SCIENCE TEAM
Dr. Richard C. WillsonPrincipal InvestigatorColumbia [email protected]
ACRIMActiveCavityRadiometerIrradianceMonitorExperiments
ACRIMSAT/ACRIM3
ACRIM INSTRUMENT TEAM
Roger S. HelizonACRIMSAT Project Mgr.
Jet Propulsion [email protected]
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• Precision TSI record spans 26 ½ years• Redundancy & overlap required for composite time series• Composite TSI traceability traceable to ~ 100 ppm end-to-end• Systematic metrology errors caused early scale differences• SI uncertainty of ACRIM2, ACRIM3 and VIRGO ~ 0.1 %• SORCE/TIM’s scale difference not currently understood
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Climate change issues related to TSI variability
The relative significance of natural and anthropogenic climate forcing has yet to be determinedClimate response to TSI variability is not well understoodClimate models of TSI forcing have large uncertaintiesThe TSI variability database on climate time scales (> decades) has just begun
TSI variation has been a significant forcing for climate change during the industrial eraPhenomenological analysis indicates ~ 50 % of global warming caused by TSI increaseSolar activity indices and Earth surface temperature anomalies correlate with TSI variability
Historical evidence indicates a direct relationship between climate change and TSI variationSustained TSI decreases ~ 0.25 % were likely causes of the ‘little ice age’ (~1450 – 1850)A comparable TSI increase was the likely cause of the medieval warm optimum (~1100 - 1400)A climate TSI record must have ~500 ppm/century resolution to detect this signal
Rationale for a Climate Total Solar Irradiance (TSI) database
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• How to provide a TSI record with calibration traceability better than ~500 ppm/century
The SI uncertainty of TSI monitoring instrumentation is inadequate (not significantly < 1000 ppm) The measurement precision of current technology is adequate (ACRIM3: ~3 ppm/yr)
• Overlapping experiments are required to provide the record using measurement precision
Traceability is transferred between successive experiments through overlapping comparisonsAt least a year of overlap required to provide maximum scale traceability
• Redundant experiments are required to prevent database interruption by satellite or instrument failures
• A redundant, overlap monitoring strategy using existing flight instrumentation is the only approach currently capable of providing a TSI database for climate change on centennial time scales with useful traceability
Monitoring Strategy for a TSI Climate Change Database
COMPARISON OF ACRIM3, VIRGO AND TIM OBSERVATIONS
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ACRIM DEGRADATION CALIBRATIONS
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* JPL Table Mtn. Solar Test Facility
‘ACRIM GAP’ COMPARISONS
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The Total Solar Irradiance Record and Its Continuity
ACRIM SCIENCE TEAM
Dr. Richard C. WillsonPrincipal InvestigatorColumbia [email protected]
ACRIMActiveCavityRadiometerIrradianceMonitorExperiments
ACRIMSAT/ACRIM3
ACRIM INSTRUMENT TEAM
Roger S. HelizonACRIMSAT Project Mgr.
Jet Propulsion [email protected]
