DETECTION OF THE CLIMATE RESPONSE TO THE SOLAR-CYCLE

Optimal space-time signal processing is used to infer the amplitude of the large-scale, near-surface temperature response to the ''11 year'' solar cycle. The estimation procedure involves the following steps. 1 ) By correlating 14 years of monthly total solar irradiance measuremen ts made by the Nimbus-7 Satellite and monthly Wolf sunspot numbers, a monthly solar irradiance forcing function is constructed for the years 1894-1993. 2) Using this forcing function, a space-time waveform of t he climate response for the same 100 years is generated from an energy balance climate model. 3) The space-time covariance statistics in the frequency band (16.67 yr)(-1)-(7.14 yr)(-1) are calculated using cont rol runs from two different coupled ocean-atmosphere global climate mo dels. 4) Using the results from the last two steps, an optimal Filter is constructed and applied to observed surface temperature data for th e years 1894-1993. 5) An estimate of the ratio of the real climate res ponse, contained in the observed data, and the model generated climate response from step 2 is given, as well as an estimate of its uncertai nty. A number of consistency checks are presented, such as using data from different regions of the earth to calculate this ratio and using data lagged up to +/- 5 yr. Our findings allow us to reject the null h ypothesis, that no response to the solar cycle is present in the data, at a confidence level of 97.4%.