Predictions that a warmer climate will lead to more rain for some but longer droughts for others might be wrong, according to a study of 12 centuries worth of data.
The study, published today in science journal Nature, found there was no difference between 20th-century rainfall patterns and those in the pre-industrial era. The findings are at odds with earlier studies suggesting climate change causes dry areas to become drier and wet areas to become wetter.
Fredrik Ljungqvist and colleagues at Stockholm University analysed previously published records of rain, drought, tree rings, marine sediment and ice cores, each spanning at least the past millennium across the northern hemisphere.
They found that the ninth to 11th and the 20th centuries were comparatively wet and the 12th to 19th centuries were drier, a finding that generally accords with earlier model simulations covering the years 850 to 2005.
However, their reconstruction “does not support the tendency in simulations of the 20th century for wet regions to get wetter and dry regions to get drier in a warmer climate”.
“Our reconstruction reveals that prominent seesaw patterns of alternating moisture regimes observed in instrumental data across the Mediterranean, western USA and China have operated consistently over the past 12 centuries,” the paper says.
The research also highlights the importance of using paleoclimate data to place recent and predicted rainfall-pattern changes in a millennium-long context, the report says.