Speaker
Description
The Sun is the primary external energy source for Earth, making reliable long-term records of solar irradiance essential. Measurements of total solar irradiance (TSI) have been available since 1978, although they originate from multiple relatively short-lived space-based missions that exhibit marked differences. Combining these observations into a consistent long-term record is therefore challenging and has resulted in several composite series, which imply conflicting long-term trends between activity minima.
To address the limited duration of direct observations, a range of modelling approaches has been developed to reproduce irradiance and reconstruct it over earlier periods. These models rely on observations for calibration and/or validation, but differ in the input data and their assumptions and treatment of solar magnetic features, leading to divergent long-term trends. Reconciling the secular trends inferred from direct TSI measurements and those from various irradiance reconstructions is therefore crucial, particularly for accurately assessing the solar influence on Earth’s climate. Here, I will give an overview of the current picture about long-term trends in direct irradiance measurements and the principal modelling approaches used to reconstruct solar irradiance.