Scientists are always looking for reliable records of past environmental conditions, so they can see if current observations are at all unusual. Good records are frequently obtained from lake sediments, which faithfully record yearly inputs of materials washed in from their watersheds. Increasingly, records taken from the ice packs on Greenland and Antarctica are used to show global changes in our atmosphere.
But, there are some unusual sources of information about past environments, as well. One comes from local newspapers, which record the first date in spring when the ice leaves a lake or river. Others come from local bird clubs, where members have recorded the first appearance of a new species or the earliest arrival of migrant birds in the spring.
One of my favorite reports uses the content of chemicals in old wines to show changes in the chemistry of our atmosphere. Radiocarbon in the atmosphere increased during the testing of atomic weapons until the early 1960s. The radiocarbon in Austrian wines shows this increase, peaking in 1963, and declining thereafter, with the advent of the Test Ban Treaty.
Similarly, lead was emitted to the atmosphere from the use of leaded gasoline until the mid-1970s. And sure enough, the lead content of wines, derived from gasoline, increases in vintage bottles laid down in the 1950s until the early 1970s, and declines thereafter.
Old wines are a faithful, but serendipitous source of information about past atmospheric conditions. In this example, the wines record an improvement in our environment as a result of human policy decisions to cleanse our atmosphere.
Photo, taken on July 12, 2006, courtesy of Guttorm Flattabo via Flickr.