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Updated: Jul 12, 2026
09:55
Surface Renewal: An Advanced Micrometeorological Method for Measuring and Processing Field-Scale Energy Flux Density Data
Published on: December 12, 2013
Long-term downward trend in total solar irradiance
Science (New York, N.Y.)
|November 28, 1986
Summary
The Active Cavity Radiometer Irradiance Monitor (ACRIM I) observed a solar irradiance decrease of 0.019% annually from 1980-1985. This trend, linked to solar magnetic activity, was verified by multiple independent measurements.
Area of Science:
- Solar physics
- Earth science
- Space physics
Background:
- Total solar irradiance (TSI) is a key driver of Earth's climate.
- Understanding long-term TSI variations is crucial for climate modeling.
- Previous satellite missions provided limited long-term TSI data.
Purpose of the Study:
- To analyze the first five years of ACRIM I total solar irradiance data.
- To identify and quantify any trends in solar irradiance during this period.
- To investigate potential causes for observed solar irradiance variations.
Main Methods:
- Utilized data from the Active Cavity Radiometer Irradiance Monitor (ACRIM I) on the Solar Maximum Mission spacecraft.
- Cross-validated ACRIM I findings with internal self-calibrations.
- Compared ACRIM I data with independent measurements from sounding rockets, balloons, and the Nimbus-7 spacecraft.
Main Results:
- A statistically significant downward trend in total solar irradiance was detected.
- The observed trend indicated a decrease of -0.019% per year.
- The trend's existence was corroborated by multiple independent data sources.
Conclusions:
- The Sun's luminosity exhibited unpredicted variations on multi-year timescales.
- These variations may be associated with the solar cycle and its associated magnetic activity.
- ACRIM I data provided crucial insights into solar variability and its potential climate implications.
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