Thirty years ago, scientists from the Smithsonian Institution, Washington, D.C., and the National Physical Laboratory, Jerusalem reported severe changes over the years in solar radiation and issued a call for a careful study of incoming radiation at different places throughout the world...to determine the exact kind, order of magnitude and their causes.... The severe changes referred to emerged from the measurements at the site of the Smithsonian Institution's former solar radiation monitoring station on Mount St. Katherine in the southern Sinai peninsula (28¿31' N, 33¿56'E, 2643 m altitude). Measurements using modern radiometers as well as some of the original instruments used between 1933 and 1937 showed a 12% loss in global radiation during the intervening four-decade interval.