1. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University1 ACRIM INSTRUMENT TEAM Roger S. Helizon, Jet Propulsion Laboratory Instrument Scientist/Project Mgr. roger@simdac.jpl.nasa.gov ACRIM Composite Total Solar Irradiance Time Series ACRIM SCIENCE TEAM Dr. Richard C. Willson, Columbia University Principal Investigator acrim@acrim.com Dr. Alex Mordvinov, Head –Solar Activity Laboratory Institute Of Solar Terrestrial Physics, Irkutsk, Russia Co-Investigator Dr. James Hansen, Director – NASA/GISS Co-Investigator Dr. Hugh S. Hudson – University of CA at Berkeley Co-Investigator

2. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University2 The Total Solar Irradiance Observational Database Continuous monitoring since 1978 by redundant, overlapping, satellite experiments Overlapping comparisons provide contiguous results at mutual precision levels Absolute uncertainty varies by experiment but is not demonstrably less than 0.1 % (SI) Traceability varies between experiments: ≥ 50 ppm/decade Scale differences of ± 0.4 % likely due to systematic errors in sensor metrology

3. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University3 0.4 %

4. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University4 ACRIM ‘gap’

5. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University5 ACRIM Composite TSI Approach Uses Original published results from TSI experiments Overlapping comparisons to relate experiments at mutual precision level Comparisons of ACRIM with Nimbus7/ERB to bridge the ACRIM ‘gap’ Reconciles Composite time series to ACRIM3 ‘native scale’

6. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University6

7. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University7

8. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University8 Comparison of ACRIM and PMOD Composite TSI

9. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University9 Composite TSI Measurements and Models ACRIM Composite TSI Uses original published results from TSI experiments Uses Nimbus7/ERB ACRIM ‘gap’ ratio to link ACRIM1 and ACRIM2 PMOD Composite TSI Modifies published results from TSI experiments Uses ERBS ACRIM ‘gap’ ratio to link ACRIM1 and ACRIM2

10. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University10 The ACRIM - PMOD Composite Trend Difference is an artifact of using the Nimbus7/ERB or ERBS ACRIM ‘gap’ ratios

11. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University11

12. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University12 Comparison of Nimbus7/ERB and ERBS results (Simultaneous Daily Means) ACRIM GAP

13. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University13 Comparison of Overlapping Observations during ACRIM1, ACRIM ‘gap’ and ACRIM2 Periods

14. SORCE Science Mtg. Dec. 2003 R C Willson - Columbia University14 Composite TSI Summary and Conclusions ERBS degradation during ACRIM ‘gap’ equals the ACRIM - PMOD trend difference PMOD adjustment of Nimbus7/ERB results during ACRIM ‘gap’ equals the ACRIM - PMOD trend difference The absence of a minimum-to-minimum trend in composite models using ERBS results to bridge the ACRIM ‘gap’ is an artifact of ERBS degradation Composite TSI time series using best extant data exhibit a minimum-to- minimum trend of + 0.04 %/decade during solar cycles 21 - 23