SALT LAKE CITY — The nagging drought in the West and frigid cold that blanketed the eastern portions of the United States this year played out with duration and effects that new research shows were amplified by greenhouse gas emissions.
A Utah State University study published in "Geophysical Research Letters" indicates a series of events that unfold in a year that is absent an El Nino or La Nina — marked by either warming ocean waters off the Pacific or cooling Pacific waters.
The absence of those conditions, the study suggests, helps to create a high-pressure system that is followed a few months later by a "ridge" that pushes the jet stream into a dip, drawing cold Arctic air to settle over the East and farther south than typical.
In the study, lead researcher Simon Wang and Robert Gillies with USU's Utah Climate Center examined the cause of the 2013-14 drought that held onto California and provoked another arid year for Utah.
In California, the ridge began in the summer of 2013 and intensified into the winter. The relentless "deepening" of the high-pressure ridge created a sort of wavelike effect, much like slapping a rope, that ultimately drove conditions ripe for the formation of a trough.
While the western ridge is blamed for the widespread drought conditions that have occurred along the West Coast, the eastern trough is associated with the series of extremely cold outbreaks across the Midwest and East Coast, the study notes.
That trough resulted in the coldest air in 20 years to settle in over the Midwest, eastern United States and the South from January to March, inflicting such extreme conditions that growth in the economy was brought to nearly a standstill.
Researchers believe the link among these weather phenomena has grown stronger since 1970, suggesting that the greenhouse gas emissions load is helping to drive more dramatic weather events from coast to coast.
"If you inject greenhouse gasses into the atmosphere, it warms the atmosphere and it makes that jet stream become wavier. The highs get higher and the lows get lower," Gillies said.
Wang said the study looked at those conditions that are a "precursor" to an El Nino.
"And the precursor itself seems amplified by a buildup of heat-trapping greenhouse gases. Then we noticed the connection between that precursor ― cold water off China, Vietnam and Taiwan ― and the recent wild winter. We tracked similar combinations of highs and lows in North America and found those combination extremes are getting stronger."
Both Gillies and Wang said the extreme nature of the weather patterns drove the desire for the study and the need to find answers.
"When the drought happened, no one saw it coming," Wang said. "No one knew it would become this big and this severe, and the drought caught everyone's attention. We began to see what is missing in these climate conditions that led to surprise for everyone."
Ultimately, they believe its findings may lead to communities being able to prepare for extreme weather.
"The hope would be that there would be that index now of some reliability," Gillies said.