Rainfall Becoming Increasingly Unpredictable Over the Last Century Due to Human Impact

Rainfall Becoming Increasingly Unpredictable Over the Last Century Due to Human Impact
by Simon Mansfield
Sydney, Australia (SPX) Jul 29, 2024

Global observations have shown that rainfall patterns are becoming more unpredictable. The frequency of intense downpours has increased, and dry periods are becoming longer and more severe. These shifts have raised alarms, prompting scientific investigations into the link between climate change and these erratic rainfall patterns.

A new study provides the first systematic observational evidence that human-induced climate change is significantly increasing rainfall volatility worldwide.

Published in the journal Science on July 26, this joint study by the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences, the University of Chinese Academy of Sciences (UCAS), and the UK Met Office documents a marked increase in rainfall variability from the 1900s to the present, observable at both global and regional scales and across daily to intraseasonal timescales.

Rainfall variability indicates the inconsistency in the timing and quantity of rainfall. Greater variability means precipitation is more irregularly distributed, resulting in more extreme wet periods and drier dry periods. Some regions may experience a year's worth of rain in just a few days, followed by prolonged dry spells or rapid shifts between drought and flooding.

While climate models have predicted that such variability would increase with future warming, this study confirms that the trend has been occurring over the past century.

By examining a broad range of observational data, researchers found that rainfall variability has increased since the 1900s over 75% of the land areas studied, particularly in Europe, Australia, and eastern North America. The data shows that daily rainfall variability has increased globally by 1.2% per decade.

"The increase in rainfall variability is mainly due to anthropogenic greenhouse gas emissions, which have led to a warmer and more humid atmosphere. This means that even if the atmospheric circulation remains the same, the additional moisture in the air leads to more intense rain events and more drastic fluctuations between them," said Dr. ZHANG Wenxia, lead author of the study and associate professor at IAP. "These changes are further influenced by regional atmospheric circulation patterns on decadal time scales."

"The future we are anxious about is already here," commented Dr. ZHOU Tianjun, a senior scientist at IAP and a professor at UCAS, as well as the corresponding author of the study. "The increased variability in precipitation we observed adds crucial evidence of larger daily changes, making it more difficult to predict and prepare for environmental impacts."

Dr. WU Peili, an expert scientist at the Met Office and co-author of the study, added, "Rapid and extreme shifts in climate patterns also pose significant risks to the climate resilience of infrastructure, economic development, ecosystem functioning, and carbon sinks." He emphasized that "immediate adaptation measures are essential to address these challenges."

Research Report:Anthropogenic amplification of precipitation variability over the past century