VIDEO: What is a Proxy?

Preview: Ice cores and tree rings are two ways that climate scientists study what the Earth was like in the past. Climate scientists determine the past conditions two very different ways:

  1. Lab #1-Direct Data Measurements  Direct measurements allow scientists to collect data directly from the source.  A good example is a rain gauge.  After a rainstorm you can make a direct measurement of how much rain fell during a storm.  Direct measurements of the CO2 level in the atmosphere are made daily on the island of Hawaii.
  2. Lab #2-Proxy Data Measurements Proxy Data are measurements that can be substituted for direct measurements when a direct measurement is not possible.  For example, it is not possible to obtain rain gauge data for a year of rainfall that happened in the 1500s.  Scientists develop proxy tools by applying relationships found in the data of direct measurements made today, to samples of trees and ice formed thousands of years ago. (See 

In this investigation data collected from tree rings will be compared to data collected from a model ice core.  Direct measurements will be used to try to determine which sample contains a longer recorded history of the Earth’s climate.