When scientists talk about climate change, they usually mean significant changes in the measures of climate over several decades or longer. Climate variability generally refers to seasonal changes over a year or so.

Lisa Goddard, an expert on climate change and variability, focuses on where the two intersect. As director of the Earth Institute’s International Research Institute for Climate and Society, based at Columbia’s Lamont campus, she looks into climate variations over a two-to-20 year time frame.