1. Click on the image to watch a 2-minute NOAA video on proxy data.

2. For a graphical summary of "climate clues" click on the image charting out proxy data over time.

2. Microscopic, single-celled organisms called foraminifera have a fossil record that extends back more than 500 million years, providing a wealth of proxy data. Click on the image to visit a Smithsonian on-line collection of beautiful foram images.