Resumen
Based on discussions at a Session of the Intergovernmental Committee on Climate Change Working Group 1 held during the period February 26 - March 2, 1990 in Great Britain, and in the context of the WG-1 Report, a review has been made of the state-of-the-art of studies on global climate change. A consensus has been reached on one of the most important conclusions that the causes of the climate warming observed during the last century remain still unclear. This determines the top urgency of studies and quantitative assessments of the internally forced variability of the climate system, without which the "filtering-out" of anthropogenic impacts on climate cannot be reliable. Such insufficiently studied factors of climate formation as ocean-atmosphere and cloud-radiation interactions are the most substantial aspects of the internal variability. The related unsolved problems have been discussed.