Extreme-weather winters more common.

• Position: Climate - Brief article

This past July was Earth's hottest month since record keeping began, but warming is not the only danger climate change holds in store. Recent years have seen a dramatic increase in the simultaneous occurrence of extremely cold winter days in the eastern U.S. and extremely warm winter days in the West, according to a study published in the Journal of Geophysical Research.

In the past three years alone, heat-related drought in the West and bitter cold spells in the East have pinched the national economy, costing several billion dollars in insured losses, government aid, and lost productivity. When such weather extremes occur at the same time, they threaten to stretch emergency responders' disaster assistance abilities, strain resources--such as inter-regional transportation--and burden taxpayer-funded disaster relief.

Understanding the physical factors driving extreme weather could provide decisionmakers with more reliable information with which to prepare for weather disasters. Meanwhile, having a grasp of the likelihood of droughts could help engineers better plan the development and management of infrastructure to provide reliable water supplies.

The study finds that the occurrence and severity of "warm-West/ cold-East" winter events, which the authors call the North American winter temperature dipole, increased significantly between 1980-2015. This partly is because winter temperature has warmed more in the West than in the East, but the authors found that it also has been driven by the increasing frequency of a "ridge-trough" pattern, with high atmospheric pressure in the West and low atmospheric pressure in the East producing greater numbers of...