A new study led by the University of California, Los Angeles (UCLA) has found that global atmospheric dust (microscopic airborne particles from desert dust storms) has a small, yet significant cooling effect on our planet, which has hidden the full amount of warming caused by greenhouse gas emissions. According to the experts, the amount of desert dust has grown by 55 percent since the mid-19th century, thus increasing its cooling effect.
While some of the effects of atmospheric dust contribute to global warming, others counteract it – for instance, by scattering sunlight back into space and dissipating high clouds that warm the planet. Overall, the researchers estimate that dust has a cooling effect.
“We show desert dust has increased, and most likely slightly counteracted greenhouse warming, which is missing from current climate models,” said study lead author Jasper Kok, an atmospheric physicist at UCLA. “The increased dust hasn’t caused a whole lot of cooling – the climate models are still close – but our findings imply that greenhouses gases alone could cause even more climate warming than models currently predict.”
Besides its atmospheric interactions with sunlight and cloud cover, when dust falls back on the Earth’s surface, it can darken snow and ice, making them absorb more heat. In addition, dust also cools the planet by depositing nutrients such as phosphorous or iron into the oceans, which support the growth of phytoplankton that absorbs CO2 from the atmosphere, thereby causing a net cooling effect.
“We want climate projections to be as accurate as possible, and this dust increase could have masked up to eight percent of the greenhouse warming,” Kok explained. “By adding the increase in desert dust, which accounts for over half of the atmosphere’s mass of particulate matter, we can increase the accuracy of climate model predictions. This is of tremendous importance because better predictions can inform better decisions of how to mitigate or adapt to climate change.”
Although atmospheric desert dust levels have increased since the pre-industrial period, this trend has not been steady, and, since there are so many natural and human-caused variables which can cause dust levels to increase or decline, scientists cannot accurately project how the amount of dust will change during the following decades. Moreover, while the increase in atmospheric dust has somewhat masked the full potential of greenhouse gases to warm the climate, the findings do not show that existing climate models are wrong.
“The climate models are very useful in predicting future climate change, and this finding could further improve their usefulness,” Kok concluded.
The study is published in the journal Nature Reviews Earth & Environment.
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