Number 30 (Story #1), April 18 1991 by Phillip F. Schewe and Ben Stein THE NATIONAL ACADEMY OF SCIENCES STUDY ON GLOBAL WARMING admits that it is difficult to make firm predictions about greenhouse effects, but does suggest that a temperature rise of 1-5 C may occur in the near future. The report recommends that certain measures, such as increasing auto fuel efficiency and further decreasing greenhouse-gas emissions, be taken to mitigate possible human-induced warming tendencies. (Science 12 April 1991.)