25. Feb 2023
(PM) A team of researchers from the USA, Norway and Germany was able to prove 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 the Forschungszentrum Jülich assume this that dust masks up to 8 percent of warming from greenhouse gases such as carbon dioxide.
If the increase in dust were to be stopped, the previously hidden additional warming potential of greenhouse gases could lead to somewhat faster global warming. The results of the study, which have now been published in the journal Nature Reviews Earth and Environment, help to further improve climate models.
Vchanged land use leads to more desert dust in the atmosphere
The researchers, including Dr. Vlassis Karydis from the Jülich Institute for the 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 geological record, collecting data from ice cores, marine sediment records and peat bog samples, all of which show layers of atmospheric dust fallen from the sky. Despite upswings and downswings, samples from all over the world showed an overall increase in the amount of desert dust – the scientists put the increase at around 55 percent since the mid-19th century. One of the reasons for this is a change in land use, especially on the edge of the world’s large desert areas.
overall effect of the dust is cooling
Some effects of atmospheric dust are warming the planet. On the other hand, the backscattering of sunlight into space and the dissolution of high clouds by dust counteract the warming. When it falls back to earth, mineral dust can darken snow and ice by settling on top of them, causing them to absorb more heat. Dust also cools the planet by depositing nutrients like iron and phosphorus. For example, when these nutrients end up in the ocean, they encourage the growth of phytoplankton, which absorb carbon dioxide from the atmosphere, causing net cooling. Overall, the study concludes that the overall effect of the dust is a cooling one.
Even greater global warming with less dust
However, since the cooling is rather moderate, the results of the study do not differ significantly from the current climate models. However, they indicate that greenhouse gases alone could cause even greater global warming. According to the researchers, this applies, for example, if the dust content falls or even just stops growing. So far, they conclude, the dust in the atmosphere covers about 8 percent of global warming caused by greenhouse gases.
The new findings help to increase the accuracy of the climate models and thus the forecasts. This is of enormous importance, as more accurate predictions can lead to better decisions about climate change mitigation or adaptation.
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).
Text: Research Center Jülich