Claim: More persistent weather patterns in US linked to Arctic warming

Rutgers-led study suggests extreme weather will become more common

Persistent weather conditions, including dry and wet spells, generally have increased in the United States, perhaps due to rapid Arctic warming, according to a Rutgers-led study.

Persistent weather conditions can lead to weather extremes such as drought, heat waves, prolonged cold and storms that can cost millions of dollars in damage and disrupt societies and ecosystems, the study says.

Scientists at Rutgers University-New Brunswick and the University of Wisconsin-Madison examined daily precipitation data at 17 stations across the U.S., along with large upper-level circulation patterns over the eastern Pacific Ocean and North America.

Overall, dry and wet spells lasting four or more days occurred more frequently in recent decades, according to the study published online today in Geophysical Research Letters. The frequency of persistent large-scale circulation patterns over North America also increased when the Arctic was abnormally warm.

These are land surface temperatures from December 26, 2017 to January 2, 2018, compared with the 2001 to 2010 average for the same eight-day period. The persistent warm West and cold East pattern that was so prevalent last winter caused a western drought that led to summer fires, a prolonged cold spell in much of the East and a parade of nor’easters along the East Coast. CREDIT NASA Earth Observatory

In recent decades, the Arctic has been warming at least twice as fast as the global average temperature, the study notes. The persistence of warm Arctic patterns has also increased, suggesting that long-duration weather conditions will occur more often as rapid Arctic warming continues, said lead author Jennifer Francis, a research professor in Rutgers’ Department of Marine and Coastal Sciences.

“While we cannot say for sure that Arctic warming is the cause, we found that large-scale patterns with Arctic warming are becoming more frequent, and the frequency of long-duration weather conditions increases most for those patterns,” said Francis, who works in the School of Environmental and Biological Sciences.

The results suggest that as the Arctic continues to warm and melt, it’s likely that long-duration events will continue to occur more often, meaning that weather patterns – heat waves, droughts, cold spells and stormy conditions – will likely become more persistent, she said.

“When these conditions last a long time, they can become extreme events, as we’ve seen so often in recent years,” she said. “Knowing which types of events will occur more often in which regions and under what background conditions – such as certain ocean temperature patterns – will help decision-makers plan for the future in terms of infrastructure improvements, agricultural practices, emergency preparedness and managed retreat from hazardous areas.”

Future research will expand the analysis to other regions of the Northern Hemisphere, develop new metrics to find causal connections, and analyze projections to assess future risks from extreme weather events linked to persistent patterns, she said.


The paper:

North American weather regimes are becoming more persistent: Is Arctic amplification a factor?
Jennifer A. Francis,  Natasa Skific,  Stephen J. Vavrus

Rapid Arctic warming is hypothesized to favor an increased persistence of regional weather patterns in the northern hemisphere [Francis and Vavrus 2012]. Persistent conditions can lead to drought, heatwaves, prolonged cold spells, and storminess that can cost millions of dollars in damage and disrupt societal and ecosystem norms. This study defines a new metric called long‐duration events (LDEs) ‐‐ conditions that endure at least 4 consecutive days ‐‐ and takes two independent approaches to assessing seasonal changes in weather‐pattern persistence over North America. One applies precipitation measurements at weather stations across the United States; the other is based on a cluster analysis of large‐scale, upper‐level atmospheric patterns. Both methods indicate an overall increase in LDEs. We also find that large‐scale patterns consistent with a warm Arctic exhibit an increased frequency of LDEs, suggesting that further Arctic warming may favor persistent weather patterns that can lead to weather extremes.

Plain Language Summary
Rapid Arctic warming and sea‐ice loss are expected to affect weather patterns around the northern hemisphere. An increased persistent of weather regimes is one hypothesized impact. Long‐lasting weather conditions can lead to destructive extreme events, such as droughts, prolonged cold spells, heatwaves, and flooding. This study uses daily precipitation measurements across the United States, as well as daily large‐scale atmospheric patterns over the eastern Pacific and North America, to assess changes in weather‐regime persistence, and whether any changes are associated with a rapidly warming Arctic. We find an increased frequency in long‐lived patterns in recent decades, especially those with abnormally warm high latitudes, suggesting that further Arctic warming may favor an increase in extreme events caused by prolonged weather conditions.

The paper is paywalled, but the SI is here: grl58052-sup-0001-2018gl080252_s01

I’m not very impressed by this paper for several reasons.

  1. They don’t seem very cognizant of long-term natural patterns as being the driver, instead assuming climate change/AGW is the driver from the get-go.
  2. They apparently only use data back to 1950, even though older data is available. This completely eliminates the dust bowl years of the 1930’s for no apparent good reason except it might not produce the results they want.
  3. Lead author is Jennifer Francis, who in my opinion is just as openly biased as Dr. Michael Mann, which makes me doubt the veracity of her work.

via Watts Up With That?

September 26, 2018 at 12:49PM

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