3-5m-year-old dust shows climate change is moving westerly winds
Dust left deep beneath the oceans three to five million years ago has confirmed that is pushing westerly winds towards the poles, say scientists. The winds, commonly known as the westerlies, play an important role in shaping the world's weather by influencing rainfall, ocean currents and tropical cyclone paths. They typically blow from west to east across the planet's middle latitudes, but over the past few decades, have shifted towards the poles. Until now, it wasn't clear whether this was the result of global warming or some other cause. However, researchers from Columbia University have examined core samples from the North Pacific and compared them to dust samples from elsewhere in the world. These samples, deposited over millions of years, confirm that the westerlies move towards the poles during warmer periods. Prior to this study there was very little knowledge about the westerlies during past periods of global warming, so confirming a link between the polar shift of the winds and global warming proved difficult. To solve this mystery, scientists from Columbia University came up with a new method of tracking the ancient history of the westerly winds. Senior author Dr Gisela Winckler said tracking movements of wind and how they've changed has been elusive as there was no tracer, adding that they now have one. They examined core samples from the North Pacific Ocean, as they knew the winds transport dust from desert regions to faraway places. The North Pacific Ocean is downwind from Eastern Asia, which has been one of the largest sources of dust for millions of years. Comparing the amount of desert dust in cores collected from sites thousands of miles apart allowed them to map changes in the dust and by proxy the westerlies. Co-author, graduate student Jordan Abell said, a pattern was immediately visible - adding that the data was so clear. 'Our work is consistent with modern observations, and suggests that wind patterns will change with climate warming,' said Abell. The westerlies moved closer to the poles during warmer periods such as the Pliocene three to five million years ago, the researchers found. During this time, the earth was 3.6 to 7.2 degrees Fahrenheit (2-4C) warmer than today with roughly the same amount of CO2 in the atmosphere. This suggests as global temperatures rise, atmospheric circulation patterns are likely to change in the same way, the researchers say. The UN Paris climate agreement commits governments around the world to take measures to keep global average temperatures from increasing by more than 3.6F over pre-industrial levels by the end of the century. This study suggests that if temperatures rise by the maximum agreed by the UN, then the winds will continue their shift towards the polar regions of the Earth. Land and ocean temperatures have risen by 1.26F (0.7C) every decade since 1880, although the rate of increase has doubled since 1981. Dr Winckler said: 'By using the Pliocene as an analogue for modern global warming, it seems likely that the movement of the westerlies towards the poles observed in the modern era will continue with further human-induced warming.' The movement of wind caused by climate change will have 'huge implications' for storm systems and weather patterns across the globe, the researchers say. While they are unable to predict exactly where it will rain, the results confirm rainfall will change as CO2 levels and temperatures continue to rise. The findings were published in the journal Nature.