Source: WeatherSTEM
The best way to gather data about climate is to take direct measurements. This could mean using instruments like a thermometer to measure temperature, for example, or a rain gauge to measure precipitation. These measurements can give a very accurate picture of the Earth’s current climate. But how do we know what the climate was like before these instruments were invented? Or before we kept written records or even had human civilizations?
The answer lies in proxy measurements. Proxy data tell us what the climate was like by leaving clues from the past. For example: each year a tree grows, it lays down a circle of new tissue called a “ring.” In years with plenty of rain and sunshine, tree grow faster, but in drought years, trees grow more slowly. By looking at the rings of very old trees, we can find out about past precipitation patterns, even though no one actually measured the rainfall.
There are many types of proxy data that can help us determine what the Earth’s climate was like a long time ago. We’ll explore some of them later in this lesson.