A "Hockey Stick graph" is a type of chart that shows a long period of relatively stable data followed by a sharp increase, resembling the shape of a hockey stick. This visual representation is often used in discussions about climate change, economics, and other fields to illustrate sudden changes or trends over time. The term gained prominence in the late 1990s, particularly through the work of Michael Mann and his colleagues, who used it to depict global temperatures. The graph highlights the contrast between historical data and recent trends, emphasizing the urgency of addressing issues like global warming.