American scientists say that variations in atmospheric dust levels affect the temperature of the Atlantic ocean far more than global warming. Research indicates that 70 per cent of the change in Atlantic temperature over recent decades has resulted from reduced dust, rather than climate change.
The new analysis comes from scientists in the US National Oceanic and Atmospheric Administration (NOAA) and the University of Wisconsin. They say that the Atlantic temperature trend has been warmer by approximately a quarter of a degree each decade since 1980: but that most of this is actually because more sunlight is reaching the sea due to reducing levels of dirt in the air above it.
"A lot of this upward trend in the long-term pattern can be explained just by dust storms and volcanoes," says Amato Evan of Wisconsin uni. "About 70 percent of it is just being forced by the combination of dust and volcanoes, and about a quarter of it is just from the dust storms themselves."
"This makes sense, because we don't really expect global warming to make the ocean [temperature] increase that fast," he adds.
Evan and his collaborators at Wisconsin and the NOAA produced their figures by combining satellite dust data with Atlantic temperature records over the last 26 years.
The researchers say that predicting what will happen to atmospheric dust levels in future is difficult, with volcanoes notoriously random and African dust storms poorly understood. Nonetheless, according to Amato, future ocean-warming models will need to make allowance for them somehow or their predictions will be well out of whack.
Quite apart from matters such as the melting of the ice caps, species survival and so on, this will apparently mean very poor prediction of hurricanes - the killer storms being driven very largely by sea temperature. The Atlantic was on average a degree warmer for the record-breaking storm season of 2005 than it was during the quiet year seen in 1994.
"Volcanoes and dust storms are really important if you want to understand changes over long periods of time," Evan says. "If they have a huge effect on ocean temperature, they're likely going to have a huge effect on hurricane variability as well."
The researchers' new paper can be read online here (abstract: full text requires subsciption). ®