“On the 31st of December, 1764, the Delaware was frozen completely over in one night, and the weather continued cold until the 28th of March with snow about two and a half feet deep.”
“The winter of 1756 was very mild. The first snow was as late as the 18th of March.”
And so it goes. 1750 was mild; 1742 “one of the coldest since the settlement of the country”; 1741 was intensely cold, 1725 mild, 1714 very mild after the 15th of January, 1697 long, stormy and severely cold. The upshot of it all is that February violets and April snows were just as well known to General Washington as they are to us.
NIMBUS
Courtesy of Richard F. Warren
Nimbus is any cloud from which rain is falling, and the important thing to know is how to judge from the formless thing how much longer it is to rain. The wind is the surest guide. In this picture the nimbus cloud is only that at the end of the cape. All the rest is torn stratus and cumulus, which needs to condense a little further before it becomes nimbus. This will likely happen because the cloud at the left is very dark. The broken appearance denotes some wind. Rain does not fall from a mottled sky nor yet a streaky one; the nimbus is uniform in appearance. In summer a break in the nimbus will show a veil of cirro-stratus above. Just nimbus by itself will not support much of a storm. In winter if the nimbus is particularly seamless snow is about to fall.
But though all facts point to the fact that the climate does not change in a decade or a generation or a dozen generations, there is some comfort for those who are not satisfied in knowing that it doesn’t stay the same forever. During the carboniferous times the poles were as warm as the tropics and when the Ice Age came on it was very chilly everywhere. If one might only live an eon or two he might then well complain of the changing climate.
Climate, however, is one thing, weather another. The climate is the sum total of the weather. Climate is as enduring as our Constitution, the weather is as changeable as our city governments. No matter how proud a scientist may be of the lasting qualities of the climate, he has to admit that our weather, taken day by day or even year by year, is versatile in the extreme. And the question he has set himself to solve is how to explain the variations of the seasonable weather. He wants to find out why all winters are not alike, and why no two successive springs are the same. Then he will be on firm ground at last and able to make scientific forecasts for the ensuing year.
The obvious thing was to find out as accurately as possible what had happened and science’s keenest eye was focused on records in the hope of discovering fixed periods of warmth or wetness, cycles of cold and drought. So far no cycles have been discovered that are beyond dispute. Nothing has been found that cannot be contradicted successfully. This is discouraging.