Armed with a hammer and a pickaxe and with a drone flying overhead, Hemmo Abels studies the sediments left by rivers that once flowed across the plains of the United States. By means of painstaking detective work he is gradually piecing together a picture of how these rivers changed over time, a process influenced in part by ancient climate change. The data he is gathering sheds light on our own subsoil when it comes to detecting hydrocarbon and geothermal reservoirs. ‘The effects of climate on river systems have been hugely under-researched.’