The scientists from the University of California, Los Angeles, Cornell University, NASA, and several European research centers have shown that desert dust heats the planet almost twice as much as estimated before. Relying not only on climate models but also satellite and ground-based observations, they have arrived at the estimate of approximately +0.25 watts per square meter, up from previous 0.13, which is a noticeable difference for the climate, as such values influence weather forecasts and our understanding how the Earth as a whole warms and cools.
The reasons for the discrepancies are in the models themselves. First, many of them fail to account for scattering of thermal radiation by dust particles, although it is this process that provides a significant portion of the overall effect. Second, the calculations underestimate the role of large dust particles. They fall out of the atmosphere more quickly and are less easily detected by observations, but it is such particles that interact most strongly with infrared radiation and contribute most to heating. As a result, the models effectively “miss” a significant portion of the dust impact.
To get a more accurate estimate, the scientists have developed an analytical model based on real data. It incorporated information on the dust size and concentration, including large particles, as well as data on temperature, humidity, and atmospheric composition. Then the researchers made a series of calculations with different parameters and selected the results matching their observations. This approach allowed them not only to obtain an average estimate but also to account for uncertainties and reduce potential errors.
Separately, the scientists analyzed distribution of this effect across the planet. They found out that it is maximum near large dust sources (for example, over the Sahara or the Asian deserts) and intensifies during warm season. This is due to the fact that the heated surface and active updrafts lift dust higher into the atmosphere. The higher and the colder a dust layer is, the more heat is trapped, as it radiates the heat back into space less efficiently than the heated surface of the Earth.
Cloud cover significantly changes the picture. If clouds are located above the dust layer, they almost completely offset this effect. If they are located below, they only partially weaken it. Therefore, in desert areas where clouds are few, dust influence remains almost entirely, while it reduces more sharply over oceans and remote regions.
Comparison with the observations shows that the new model describes the real situation much more accurately than the traditional climate models systematically underestimating the dust influence.
The practical implications of this conclusion are quite broad. Underestimation of the contribution of dust results in errors in the temperature, cloudiness, and precipitation calculations. This means that both short-term weather forecasts and long-term climate scenarios may be less accurate. For example, the influence of dust on clouds and evaporation can alter precipitation distribution having implications for water resources, agriculture, and drought risks.
However, the key question remains open. Dust acts in two ways: it reflects sunlight, thereby cooling the Earth, but at the same time it holds back heat emission and warms the atmosphere. Which of these components is ultimately stronger remains unclear at the global level.
