Big climate changes in the last million years might have come from something very small: dust from outer space. Earth alternates between ice ages and warm periods in a pattern that incorporates several cycles, including a mysterious one that lasts 100,000 years. Scientists recently suggested that this cycle might be due to changes in the influx of cosmic dust.
Now, Caltech researchers report in the journal Nature that they have recovered ancient cosmic dust in ocean floor drilling near the Azores islands west of Portugal. The abundance of the dust rises and falls in a 100,000-year cycle, and periods of more dust correlate with warm climates.
But that's a long way from showing that the dust affects climate, warns Caltech researcher Kenneth Farley. For one thing, it is not clear how cosmic dust would make the climate warmer while dust from volcanoes is known to make it cooler, he said. The cosmic dust is so sparse it is also hard to see how it could have any climate effect, he said.