Precipitation becomes more and more irregular over time. Intense downpours are more frequent, and dry periods seem to last longer and become more severe. These changes have caused concern and prompted scientists to investigate the links between climate change and these irregular fluctuations in precipitation.
The new study presents the first systematic observational evidence that human-induced climate change is causing rainfall to become more erratic around the world over time.
A joint study by the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences, the University of the Chinese Academy of Sciences (UCAS) and the UK Met Office, published in the journal Science, demonstrates a systematic increase in precipitation variability since the 1900s, from global to regional scales and from diurnal to intra-seasonal.
Precipitation variability refers to the unevenness in the timing and amount of precipitation. Higher variability means that precipitation is unevenly distributed over time, resulting in wetter wet periods and drier dry periods. For example, some places may receive annual rainfall in just a few days, there may be long dry periods followed by heavy rainfall, or drought and flooding may alternate rapidly.
Although climate models predicted that this variability would increase with future warming, this study confirms that such an increase has already manifested itself over the past century.
After analyzing a wide range of observational data, the researchers found that rainfall variability has increased since the 1900s in 75% of the areas surveyed, especially in Europe, Australia and eastern North America. The researchers found that daily rainfall variability increased globally by 1.2% over the decade.
“The increase in precipitation variability is mainly due to anthropogenic greenhouse gas emissions, which have led to a warmer and wetter atmosphere. This means that even if atmospheric circulation remains the same, the additional humidity in the air will lead to more intense rainfall and sharper fluctuations in between,” said Zhang Wenxia, lead author of the study and assistant professor at the IAP. “These changes are further influenced by regional atmospheric circulation patterns on decadal timescales.”
“The future we were worried about is already here,” said Zhou Tianjun, a senior scientist at the IAP and a professor at UCAS. “The increased variability in precipitation that we observed adds important evidence of larger daily changes, making it more difficult to predict and prepare for environmental impacts.”
According to Dr. Wu Paley, an expert scientist at the Met Office and co-author of the study, “Broad and rapid fluctuations between climate extremes not only challenge the existing capabilities of current weather and climate forecasting systems, but also have cascading effects on human society, threatening the climate resilience of infrastructures, economic development, ecosystem functioning, and terrestrial carbon sinks.” In addition, he noted that “Immediate adaptation measures are critical to address these challenges.”
Climate change is making rainfall more erratic (planet-today.ru)
