Fossilised rodent urine a critical piece of climate history puzzle

Fossilised rodent urine has helped researchers make a crucial climate discovery. Australian National University scientists have created a coherent picture of abrupt climate change at the end of the last Ice Age. During this period, Antarctica suddenly stopped warming and began to cool down for almost 1500 years. At the same time, the Northern Hemisphere warmed rapidly. Researchers have brought evidence of the complex variations in earth’s climate during this period together in a single study. This involved collecting samples, which give a temperature record. Samples included ice cores from Antarctica, cave samples from Northern Australia and stalagmites of fossilised rodent urine from rock hyraxes – a South African rodent. These spots where these animals urinate and defecate become middens – refuge heaps – and some are almost 30,000 years old. They have rich pollen records that researchers use to understand changes in plant dynamics over time. Paleoclimatologist Dr Brian Chase, of France's Centre National de la Recherche Scientifique used this trait to understand past changes in precipitation. “It was a combination of pulling together these existing climate records and trying to understand them in one new big synthesised story,” said research team member Claire Krause, from ANU. “The Northern Hemisphere warmed abruptly during this event. At the same time, the Southern Hemisphere cooled. Depending on where you were on the earth, you [would have seen] a very different response to this particular climate event.” The cause of this event is unknown. One popular hypothesis is it was caused by disruptions in ocean circulations, as they transport heat around the globe. This could have resulted in a build up of heat in some areas and an absence in others. However, other findings from the research complicate this theory, as atmospheric circulation compensated for the ocean’s heat transport. “The compensation is imperfect," said Dr Joel Pedro from the University of Copenhagen, also a member of the team. "Climate changes in different locations throughout the Southern Hemisphere reflect the battle between the opposing ocean and atmospheric heat transport mechanisms.” The research is published in Nature Geoscience.