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B. How Glaciers Leave Behind Traces of the Past

Narrator: This is Science Today. To understand the rates of climate change, researchers often look to the geologic record to find answers. Lewis Owen, an associate professor of geology at the University of California, Riverside, says by understanding the past, researchers can try to predict what will happen in the future. Owen maps out and dates deposits where glaciers had existed over the last 20 thousand years.

Owen: Glaciers pick up rock, they erode mountainsides and they carry this rock - they're transporting agents essentially and when they melt away, they leave these rock deposits behind and these are called moraines.

Narrator: Owen has been mapping out moraines in southern California's San Bernardino mountains by walking in the field and using aerial photographs to reconstruct how extensive the ice had been.

Owen: The only way of predicting the future, really, is to develop computer models to mimic what may happen if you increase the amount of greenhouse gases in the atmosphere - but the only way we can test those is by looking at past evidence and run those models backwards, essentially, to see if those models work for times in the past that we know what the conditions were.

Narrator: For Science Today, I'm Larissa Branin.