Solar irradiance, or the amount of sunlight reaching Earth, varies over time. Scientists have been studying these variations for over 20 years and found that they change on different time scales, from minutes to the 11-year solar cycle. Recent measurements show that the amount of sunlight at different wavelengths also changes, with more variation at shorter wavelengths. While it was previously thought that these changes were mainly due to solar activity, new data suggests that other factors like global temperature changes may also play a role. Overall, the research shows that solar and UV irradiances were higher during the peak of solar cycle 23 than expected based on magnetic activity alone.