Historical increase of desert dust in the atmosphere is masking greenhouse gases' warming effect
January 25, 2023
A team of researchers from the United States, Norway and Germany has demonstrated for the first time that the increase in atmospheric desert dust since the mid-19th century has had an overall cooling effect on the Earth. The scientists from the University of California (UCLA, Merced, San Diego), Cornell University (Ithaca, New York), the National Center for Atmospheric Research in Boulder (Colorado), the University of Oslo and Forschungszentrum Jülich believe that the dust masks up to 8 percent of the warming caused by greenhouse gases such as carbon dioxide. If the increase in dust were halted, the previously hidden additional warming potential of greenhouse gases could lead to somewhat faster climate warming. The results of the study, now published in the journal Nature Reviews Earth and Environment, help to further improve climate models.
The researchers, including Dr. Vlassis Karydis of Jülich Institute of Troposphere, used satellite and ground measurements to quantify the current amount of microscopic mineral particles in the air. They found that there are 26 million tons of such particles worldwide. Next, they examined the geologic record, collecting data from ice cores, marine sediment records and samples from peat bogs, all of which show atmospheric dust falling from the sky. Samples from around the world showed an overall increase in the amount of desert dust, despite ups and downs - the scientists put the increase at about 55 percent since the mid-19th century. One of the causes is a change in land use, especially at the edge of the world's large desert areas.
Some effects of atmospheric dust are warming the planet. In contrast, the backscattering of sunlight into space and the dissipation of high clouds by dust counteract warming. When it falls back to Earth, mineral dust can obscure snow and ice by settling on them, causing them to absorb more heat. Dust also cools the planet by depositing nutrients such as iron and phosphorus. When these nutrients end up in the ocean, for example, they promote the growth of phytoplankton, which absorbs carbon dioxide from the atmosphere, causing net cooling. Overall, the study concludes that the overall effect of dust is a cooling one.
However, because the cooling is rather moderate, the study's results do not differ significantly from current climate models. They do suggest, however, that greenhouse gases alone could cause even more warming of the climate. That would be true, for example, should dust levels drop or even stop growing, the researchers said. So far, they conclude, dust in the atmosphere is masking about 8 percent of global warming from greenhouse gases.
The new findings help increase the accuracy of climate models, and thus predictions. This is hugely important because more accurate predictions can lead to better decisions about mitigating or adapting to climate change.
Original publication:
Kok, J.F., Storelvmo, T., Karydis, V.A. et al. Mineral dust aerosol impacts on global climate and climate change. Nat Rev Earth Environ (2023). https://doi.org/10.1038/s43017-022-00379-5
