According to a recent study that examined decades’ worth of satellite records to demonstrate the connection, periods of severe drought and excessive rainfall are occurring more frequently as a result of global warming.
While climate models and scientists have predicted that droughts and pluvials will become more frequent and intense as the world warms, as well as anecdotal evidence based on what we see, Matthew Rodell, a NASA hydrologist and co-author of the study, told weather.com that this theory has been challenging to prove. In order to demonstrate that extremes in the water cycle have become more common, “our study was the first to use worldwide, satellite-based observations of terrestrial water storage.”
Rodell and his team calculated the total amount of groundwater, soil moisture, lake and river water, snow and ice, or “all the water stored on and in the land,” and found that there were four extreme water cycle events from 2015 to 2021, which also happened to be the seven hottest years in the modern record. There were just three significant events annually between 2002 and 2014.
“Furthermore, we discovered a strong, significant correlation between global mean temperature and global total intensity of droughts and pluvials, which had never been shown before,” added Rodell, who serves as the NASA Goddard Space Flight Center’s deputy director of Earth sciences for hydrosphere, biosphere, and geophysics.
As meteorologist Kait Parker of weather.com says, “Warmer air temperatures boost evaporation, which causes droughts to begin and endure more quickly. Yet, the moisture must go somewhere, and this is what is causing intense rainfall events. When the temperature rises by one degree celsius, the atmosphere can store 7% more water. The increased frequency of intense rainstorm events is a result of the increased water vapor.”
The researchers used data from the GRACE and GRACE-FO satellites to characterize 1,056 extreme occurrences that occurred between 2002 and 2021 for the study, which was published in the journal Nature.
The heavy rainfall event, or pluvial, that started in central Africa in 2019 and is still happening, was the most intense one that was found. The rain has caused Lake Victoria, which lies on the border between Kenya and Uganda, to rise by more than 3 feet.
A drought in Brazil in 2015 and 2016 that depleted reservoirs and forced water restriction in certain towns was the most severe dry period to occur in the previous 20 years.
The other study author, Bailing Li, stated in a NASA news release that while both episodes were linked to climatic variability, the Brazilian drought happened in 2016, the warmest year on record, demonstrating the effects of global warming. The recent droughts in the southwest United States and southern Europe were among the most severe ones ever, in part because of anthropogenic global warming.
The study looked at the relationships between other significant climatic indicators such the El Nio Southern Oscillation and global total intensity.
Although ENSO and the other oscillations undoubtedly have an impact, Rodell noted that they are not nearly as closely associated as the global mean temperature.
The frequency and severity of droughts and pluvials will likely continue to increase as the planet heats, according to our analysis, but the specifics are impossible to forecast, he added.
Rodell expressed optimism that further advancement and use of energy-efficient and renewable technology will result in a reversal of the current trend in climate change.
Continuous monitoring is essential because it gives people motivation to take action, he said. “… We must keep creating and using cutting-edge tools for monitoring and comprehending climate change.”