El Niño is the periodic warming of the equatorial Pacific Ocean that takes place every few years. In the last two decades it has been returning more often, bringing with it floods, fires and devastation across the globe. Some scientists suspect that the frequency and ferocity of El Niño owe something to global warming.

Bernard Francou, a French glaciologist and mountaineer, hopes to test this theory by extracting an ice core from deep inside an Andean glacier. Since the ice has never melted, he believes that it will provide an archive of climatic change over thousands of years.