Scientists say "flash droughts" - marked by rapid onset and quick loss of moisture from plants and soil - are increasing globally as climate change leads to higher temperatures and shifting precipitation patterns around the world.
Droughts have typically been a slow-onset phenomenon that can persist for months or years because of a lack of rainfall.
However, a study led by Chinese scientists found there has been a global transition from slow-growing droughts to flash droughts that develop rapidly and can become severe in a matter of weeks.
Unlike slow-developing droughts, which are caused by a decrease in precipitation over time, flash droughts occur when there is low precipitation along with other factors such as high temperatures, which can quickly increase evaporation and remove water from soil and vegetation.
The concept of flash droughts was proposed in the early 2000s, but it did not gain much attention until a severe drought hit the United States in the summer of 2012, according to the study, which was published in Science on Thursday.
That flash drought was considered one of the most severe droughts in the US since the 1930s and led to more than US$30 billion in economic losses.
Last summer, China was hit by its most severe drought and heatwave in six decades, affecting electricity supply, food and factory production.
Previous studies found that human-induced climate change has increased the frequency of flash droughts in southern Africa and China, but the new study aimed to investigate whether there has been a transition from slow to flash droughts at the global scale.
The authors categorised more than six decades of subseasonal droughts, which last between two weeks and three months, as either flash or slow droughts based on their onset speed or how quickly soil moisture declined.
They then calculated the ratio of flash droughts to total subseasonal droughts as well as the speed of onset to see if there had been a global trend towards flash droughts.
They found that "subseasonal droughts … developed faster and shifted from slow to flash droughts at a global scale" between 1951 and 2014.
Over 74% of global regions - the Amazon and West Africa being the exceptions - saw an increase in both the ratio of flash droughts and drought onset speed during the 64-year period, according to the study.
The transition to flash droughts was most notable in North and East Asia, Australia, Europe, the Sahara and the western coast of South America.
"The results suggest that the transition to flash droughts is more stable and rapid in a warmer future, and the higher-emission scenario would lead to a greater risk of flash droughts with quicker onset, which poses a substantial challenge for climate adaptation," the study said.
Justin Sheffield, a co-author of the study and a professor at the University of Southampton in Britain, said climate change had effectively sped up the onset of droughts.
"While it varies between different regions, there has been a global shift towards more frequent flash droughts during the past 64 years," Sheffield was quoted as saying on the university's website.
"As we head towards a warmer future, flash droughts are becoming the new normal."
The transition to flash droughts may have irreversible impacts on terrestrial ecosystems and raise challenges for drought monitoring and prediction, according to the authors.
Yuan Xing, lead author of the study and a professor at the Nanjing University of Information Science and Technology, said a deeper understanding of the causes of flash droughts was needed.
That would allow scientists to design high-resolution models and develop early warning technologies to provide more reliable scientific tools to cope with flash droughts in the context of global warming, Yuan told news site The Paper on Friday.
"Early warnings for flash drought onset on the scale of a few weeks could be hugely beneficial for mitigating their impacts and managing the risk of this new normal," the study concluded.
