When we talk about climate change, as might occur, for example, from global warming, we generally mean smooth and relatively slow changes over periods of many decades, or even centuries. But researchers studying ice cores have found evidence in the past of abrupt temperature swings that occurred over periods as short as ten years, suggesting that such relatively quick changes might also occur in the future.

Dr. Richard Alley from Penn State University is one of the researchers. He likens abrupt climate changes to building a tower of blocks. At first, blocks can be added on top and the tower remains stable, but once a certain threshold is crossed, the tower becomes too tall and abruptly topples.

It's good to know this kind of abrupt "toppling" of the climate has happened in the past because the computer models that we're currently using to simulate future climates all tend to change smoothly. Thus, they do a poor job of capturing abrupt changes like the ones Alley has discovered.