Solar Cycle Influence on Climate: Recent Evidence Ka-Kit Tung [[email protected]], Dept. of Applied Mathematics, University of Washington, Seattle It has long been suspected that the variations in the Sun’s irradiance can affect the climate near the Earth’s surface. Although evidence of solar influence in the upper atmosphere is strong, the signal to noise ratio becomes small near the surface. Even so, the annual rate of warming from solar min to solar max is comparable to that due to greenhouse gases. We can no longer claim that we are studying the Sun’s influence on climate without confronting the problem near the Earth’s surface. Recent observational and modeling evidence will be reviewed. Response to the known solar forcing is a helpful measure of climate sensitivity, and can be used to calibrate model predictions of future climate change to greenhouse radiative forcing.