Temperature response of Earth to the annual solar irradiance cycle
  We directly determine the sensitivity and time delay of Earth's surface temperature response to annual solar irradiance variations from 60 years of data. A two-layer energy balance model is developed to interpret the results. Explaining both the resulting low sensitivity and time delay of 1-2 months requires negative feedback. 
David H. Douglass (Univ. of Rochester), Eric G. Blackman (Univ. of   Rochester), Robert S. Knox (Univ. of Rochester)