No less a scholar and politician than Thomas Jefferson made observations on the phenomenon of global warming, way back in 1781 when he wrote:
"A change in our climate, however, is taking place very sensibly. Both heats and colds are become much more moderate, within the memory even of the middle aged. Snows are less frequent and less deep. They do not often lie, below the mountains, more than one, two, or three days, and very rarely a week. They are remembered to have been formerly frequent, deep, and of long continuance. The elderly inform me, the earth used to be covered with snow about three months in every year. The rivers, which then seldom failed to freeze over in the course of the winter, scarcely ever do so now. "
People have the impression that the winters were always worse. There was always more snow and it was always colder. Is this true? I think it is typical human perception that it was always colder, snowier, etc, and Jefferson's writings provide a bit of evidence to this.
Thomas Jefferson, Notes on the State of Virginia, p 207 http://etext.virginia.edu/toc/modeng/public/JefVirg.html