Human-induced climate change making rainfall more erratic: study

By Stephen Beech via SWNS

Rainfall patterns have become increasingly "erratic" over the past 100 years - and man is to blame, according to new research.

Many people around the world have noticed that the amount and timing of rain is becoming ever more difficult to predict.

Intense downpours are occurring more frequently, while dry periods seem to last longer and become more severe.

The changes have raised concerns and prompted scientists to investigate the links between climate change and unpredictable rainfall patterns.

The new research, published in the journal Science , is the first systematic observational evidence that human-induced climate change is making rainfall patterns more volatile worldwide.

The joint study by the UK Met Office, the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences and the University of Chinese Academy of Sciences (UCAS) shows a "systematic increase" in rainfall variability since the 1900s from global to regional scales and from daily to intra-seasonal timescales.

The researchers explained that rainfall variability refers to the unevenness in the timing and amount of rain.

Higher variability means that precipitation is more unevenly distributed over time, resulting in wetter wet periods and drier dry periods. For example, some places may receive a year's worth of rain in just a few days, have long dry spells followed by heavy downpours, or alternate rapidly between drought and flooding.

While climate models have predicted that variability will increase with future warming, the new study confirms that the pattern has already emerged over the past century.

The research team found that rainfall variability has increased since the 1900s over 75% of the land areas studied, particularly in Europe, Australia, and eastern North America.

They also found that daily rainfall variability has increased globally by 1.2% per decade.

Study lead author Professor Zhang Wenxia, of IAP, said: "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.

"These changes are further influenced by regional atmospheric circulation patterns on decadal time scales."

Corresponding author Dr. Zhou Tianjun, a senior scientist at IAP, said: "The future we are anxious about is already here.

"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."

Co-author Dr. Wu Peili, an expert scientist at the Met Office, 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 warned that "immediate adaptation measures" are "essential" to address challenges posed by the change in weather patterns.

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