June 24, 1988: Global Warming Has Begun, Expert Tells Senate - New York Times
...today Dr. James E. Hansen of the National Aeronautics and Space Administration told a Congressional committee that it was 99 percent certain that the warming trend was not a natural variation but was caused by a buildup of carbon dioxide and other artificial gases in the atmosphere.
If the current pace of the buildup of these gases continues, the effect is likely to be a warming of 3 to 9 degrees Fahrenheit from the year 2025 to 2050, according to these projections. This rise in temperature is not expected to be uniform around the globe but to be greater in the higher latitudes, reaching as much as 20 degrees, and lower at the Equator.
The rise in global temperature is predicted to cause a thermal expansion of the oceans and to melt glaciers and polar ice, thus causing sea levels to rise by one to four feet by the middle of the next century.
...Dr. Hansen, who records temperatures from readings at monitoring stations around the world, had previously reported that four of the hottest years on record occurred in the 1980's. Compared with a 30-year base period from 1950 to 1980, when the global temperature averaged 59 degrees Fahrenheit, the temperature was one-third of a degree higher last year. In the entire century before 1880, global temperature had risen by half a degree, rising in the late 1800's and early 20th century, then roughly stabilizing for unknown reasons for several decades in the middle of the century.