Written By: Emma Websdale
Human activities that emit greenhouse gases and cause stratospheric ozone depletion are intensifying storms and redistributing global rainfall, warns a new study.
New research by climate scientists at Lawrence Livermore National Laboratory in California has discovered links between human-induced climate change and global precipitation (rainfall) shifts.
Although previous studies have postulated that greenhouse gas emissions will intensify storms and rainfall, they have struggled to find ‘fingerprints’ –observed climate patterns that match human activity.
This new study, published in the journal Proceedings of the National Academy of Sciences, has identified these ‘fingerprints’ and reports that strengthening and migrating storms of the past 30 years have not been influenced solely by natural climate variability, but have also been impacted by human-induced greenhouse gases.
“It’s worth saying that this is another grain of sand on that vast pile of evidence that climate change is real and is occurring”, says Kate Marvel, co-author of the study.
To reach their conclusions, researchers developed a statistical method which isolated human influences from natural variations in rainfall, based on comparisons between climate model predictions and global observations from 1979-2021.
The report pulled up two key results. First, increasing temperatures intensify the hydrological cycle (water cycle), making wetter regions wetter and dry areas drier. Second, alterations in atmospheric circulation patterns cause changes in storm tracks, pushing current subtropical dry zones toward the poles.
The study’s scientists state that the occurrence of both these results simultaneously in rainfall cannot be explained by natural variability alone. This means that external influences, including human-induced greenhouse gases, are responsible for causing recent changes in rainfall and storm patterns.
“In combination, man-made increases in greenhouse gases and stratospheric ozone depletion are expected to lead to both an intensification and redistribution of global precipitation”, says Céline Bonfils, co-author of the study. “The fact that we see both of these effects simultaneously in the observations is strong evidence that humans are affecting global precipitation.”
Bonfils added, “We have shown that the changes observed in the satellite era are externally forced and likely to be from man.”
The paper warns that alterations in rainfall patterns are one of the most challenging consequences of climate change, as many societal and natural cycles that depend upon water availability will most likely need to respond to changes in the hydrological cycle in years to come.