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Climate change doesn’t follow the rules

New research suggests the drier-gets-drier and 
wet-becomes-wetter rule of thumb is broken

Areas that have traditionally been considered drought prone could actually become wetter under climate change.  file photo

New research is challenging the theory that climate change will cause drier areas to get drier and wetter areas to become wetter.

The simplified formula, based on models and observations, is inaccurate most of the time, a team of climate researchers suggests in Nature Geoscience.

An evaluation of trends in specific regions’ humidity and dryness by researchers with the Zurich-based Institute for Atmospheric and Climate Science found no clear trends towards a drier or wetter climate across three-quarters of the land area studied. There were solid trends in the remaining quarter. However, only half of that surface area followed the DDWW principle.

Some regions which should have become wetter, according to the simple DDWW formula, have actually become drier in the past — this includes parts of the Amazon, Central America, tropical Africa and Asia. On the other hand, there are dry areas that have become wetter: parts of Patagonia, central Australia and the Midwestern United States.

The ‘wet-gets-wetter’ rule is largely confirmed for the Eastern United States, Northern Australia and northern Eurasia. ‘Dry gets drier’ also corresponds to indications in the Sahel region, the Arabian Peninsula and parts of Central Asia and Australia.

“Our results emphasize how we should not overly rely on simplifying principles to assess past developments in dryness and humidity,” said lead author Peter Greve. This can be misleading, as it cannot do justice to the complexity of the underlying systems.

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