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Global warming may drive more active La Niña pattern

Broad tree-ring record provides accurate ENSO history

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Researchers say tree ring records show that El Niño activity during the 20th century has largely been outside the range of natural variability.

By Summit Voice

Climate scientists have long suspected that global warming has an influence on the Pacific Ocean El Niño- La Niña cycle (El Niño-Southern Oscillation), but instrumental records tracking the shift between above- and below average sea surface temperatures don’t go back far enough to provide context for any recent changes in the pattern.

But scientists working at the International Pacific Research Center, University of Hawaii at Manoa say a new tree ring record extending back about 700 years has helped decipher long-term trends. The tree ring samples from both the tropics and mid-latitudes in both hemispheres support the idea that the unusually high ENSO activity in the late 20th century is a footprint of global warming said Jinbao Li, lead author of the study published online in the journal Nature Climate Change. Continue reading

Climate: For El Niño, timing is everything

Study identifies wind patterns that could lead to better El Niño forecasts

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El Niño affects global weather patterns.

By Summit Voice

SUMMIT COUNTY — Climate researcher say they’ve discovered an atmospheric pattern that helps explain why El Niño often peaks during the first part of winter and usually fades away in late winter and early spring.

El Niño phases are part of a cycle when sea surface temperatures in the equatorial Pacific Ocean are warmer than average. The various phases of the so-called ENSO can have pronounced impacts on weather around the globe, spurring droughts in some areas and flooding in others.

The new study from the University of Hawai’i at Manoa Meteorology Department and International Pacific Research Center identified an unusual wind pattern that straddles the equatorial Pacific during strong El Niño events and swings back and forth with a period of 15 months as a key driver in the annual cycle. The findings were reported in the May 26 online issue of Nature Geoscience. Continue reading

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New research may help pinpoint Asian monsoon

Regional pressure fluctuations the key to unraveling monsoon mysteries

The first week of August 2010 brought extreme flooding and landslides to many parts of Asia. By August 11, floods in the Indus River basin had become Pakistan’s worst natural disaster to date, leaving more than 1,600 people dead and disrupting the lives of about 14 million people, reported Reuters. Across the border in northeast India, flash floods killed 185 with 400 still missing, reported BBC News. Floods in North Korea and northeast China buried farmland and destroyed homes, factories, railroads, and bridges. And in northwest China, rain triggered a massive landslide that left 702 dead with 1,042 missing, reported China’s state news agency, Xinhua. All of these disasters occurred as a result of unusually heavy monsoon rains, depicted in this image.

The first week of August 2010 brought extreme flooding and landslides to many parts of Asia. By August 11, floods in the Indus River basin had become Pakistan’s worst natural disaster to date, leaving more than 1,600 people dead and disrupting the lives of about 14 million people, reported Reuters. Across the border in northeast India, flash floods killed 185 with 400 still missing, reported BBC News. Floods in North Korea and northeast China buried farmland and destroyed homes, factories, railroads, and bridges. Photo courtesy NASA Earth Observatory.

By Summit Voice

FRISCO — Hawaii-based scientists say that tracking hemispheric climate patterns can help develop more accurate forecasts for the critical Asian monsoon season, which is critical to  the agriculture, economy, and people in the region.

Better monsoon forecasts have been a sort of Holy Grail for meteorologists, but season  seasonal predictions of these two types of weather phenomena are still poor. But the research done at the International Pacific Research Center, University of Hawaii at Manoa, shows the strength of the East Asian summer monsoon and  storm activity in the western North Pacific depend on fluctuations in the western Pacific Subtropical High, a major atmospheric circulation system in the global subtropics centered over the Philippine Sea.

When this system is strong in summer, then monsoon rainfall tends to be greater than normal over East Asia, and in the western North Pacific there tend to be fewer tropical storms that make landfall. Continue reading

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