The solar irradiance is the primary natural energy input into Earth’s atmosphere and climate system. Understanding the long-term variations of the solar irradiance over time scales of the 11-year solar activity cycle and longer is critical for many Sun-climate research topics. There are satellite measurements of the solar irradiance since the 1970s that contribute to understanding the solar cycle variability over Solar Cycles 21 to 24. A summary of these satellite total solar irradiance (TSI) measurements and spectral solar irradiance (SSI) measurements, which are primarily in the ultraviolet and only recently in the visible and near infrared, will be presented. A limiting factor for the accuracy of the solar cycle variability results is the uncertainties for the instrument degradation corrections, for which there are fairly large corrections relative to the amount of solar cycle variability at some wavelengths.
Examining solar irradiance trends using a new analysis technique is helping to identify some uncorrected instrumental trends, which once applied to the solar irradiance trends has the potential to provide more accurate solar cycle variability results. This new technique examines the solar irradiance trends at different levels of solar activity to indicate long-term corrections for a solar irradiance record. One of the most common components of these derived long-term trends is a downward trend that we attribute to being most likely from uncorrected instrument degradation. Examples of this analysis will be presented for some of the satellite measurements to demonstrate this new technique. These new results have the potential to improve the understanding of solar cycle variability and to clarify the uncertainties of the trends for later combining different sets of TSI and SSI observations to make composite time series of the solar irradiance from the 1970s to the present time.
Mode of presentation: oral (Need to be confirmed by the SOC)