Greenhouse gases and atmospheric particles produced by humans have influenced global drought since at least the early 20th century, according to a study from NASA’s Goddard Institute for Space Studies.
Researchers compared several data sources to construct an overall picture of shifting global drought patterns since the Industrial Revolution. They tested soil samples for moisture, consulted precipitation records, and analyzed tree rings in order to determine whether real-world wetting and drying changes aligned with predictions about human influence on drought patterns.
In order to draw these conclusions, researchers also used the Palmer Drought Severity Index (PDSI). NASA’s current method of obtaining soil moisture data by satellite dates back only to the 1980s, so using PDSI data allowed researchers to access information from before that time.
The study, published in Nature, found that the predictions of human influence on drought began to align with real-world drought data around the early 20th century, after the Industrial Revolution. Despite the influx of greenhouse gases contributing to warmer temperatures since the first half of the 20th century, researchers detected a brief respite in this pattern between 1950 and 1975.
Due to particles in the atmosphere in the form of soot, smoke, and sulfur dioxide produced by industrial activity, researchers believe that air pollution temporarily prevented greenhouse gases from creating a warmer climate and causing drought. During this time, researchers detected a wetter period and cooler temperatures. With the implementation of anti-pollution legislation, scientists began to see a return to the previous pattern that more closely aligns with their predictions.
Study co-author Kate Marvel told Science Daily that the ability to look at the worldwide impact of human beings on drought is what makes this study an innovative research project. Previous studies on this topic have been unable to establish a concrete link between humans and drought patterns, according to co-author Ben Cook.
The increased prevalence of droughts is thought to contribute to issues such as wildfires and food and water shortages.