“The debate on global warming has shifted. Worldwide, tailpipes and smokestacks spew 25 billion tons of carbon dioxide every year, and there's no longer doubt that this gas is heating the Earth. The new questions center around how much will our climate change, and how fast.”

Evidence hints the tipping point may have already been breached.

Stories gathered from correspondents and reporters across the globe reveal evidence of climate change. National Public Radio broadcasts this continuing audio series, along with text introductions.