Analyzing data from 19 climate models, they concluded that much of central and northern Europe will be five times more likely to suffer very wet winters during this century. They also predict the Asian monsoon region will experience a five-fold increase of very wet summers.
Building Better Models
In both studies the scientists tied the increase in extreme climatic conditions to a rise in global temperatures driven largely by an increase in atmospheric greenhouse gases resulting from human activities.
These gases, primarily carbon dioxide, methane, and nitrous oxide, trap heat in the atmosphere, causing an increase in temperature. The increase in temperature sparks an increase in evaporation. "Warm air can hold more water," said Milly. "[Clouds] tend to suck more water up out of the ocean, and it has to drop sometime."
But climate modeling has limitations, and the authors warn that several factors could skew the results of the trend analyses. Carbon dioxide emissions are overestimated in the models, for example, because other gases such as methane are not included. Sulphate aerosols, which tend to have a cooling effect, are also not included in the computations. In addition, changes in global vegetation and land use could affect the accuracy of the models.
In a related article, Reiner Schnur of the Max Planck Institute for Meteorology in Germany argues that studies such as these make a strong case for improving computational resources in climate research so the results will be useful to decision makers.
"Until computational power increases significantly, climate scientists will have to patch models together, taking the results of ensemble climate projections, for example, and inserting their output into a high-resolution hydrological model for a specific river basin," he writes.
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