About these ads

Global warming may drive more active La Niña pattern

Broad tree-ring record provides accurate ENSO history

fghj

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

About these ads

New study helps pinpoint El Niño impacts

Findings could help improve long-range winter forecasts

sdfg

Shifting cycles of warmer and cooler water in the central Pacific influence weather patterns around the world.

By Summit Voice

FRISCO — A new study that sorts El Niño events into two categories could help forecasters develop better long-range forecasts to predict how the periodic warming of equatorial East Pacific waters may affect winter weather.

Part of the data for the research came from an array of buoys across the Pacific called the TAO-Triton array. The buoys observes conditions in the upper ocean to forecast El Niño months in advance, and for monitoring it as it grows and decays.

After analyzing all El Niño events since 1979, the NOAA and University of Washington scientists said the El Niños that show a drop in outgoing long-wave radiation from the tops of deep convective clouds are the ones that tend to play havoc with winter weathers. Continue reading

Colorado: A warmup, but no snow in sight

Drought expected to persist; water supply outlook grim

sdfg

Colorado’s snowpack hasn’t been above average since the big winter of 2010-2011.

By Bob Berwyn

FRISCO — Temperatures will begin to moderate across the Colorado high country the next few days, with highs climbing back to near seasonal norms, which is only in the lower 30s, but that should feel downright balmy after enduring an Arctic air mass the past few days.

klj

Dry conditions persisted across Colorado in the autumn of 2012, especially in the plains.

The nicest weather will be up on the mountain slopes, because warmer air aloft will trap cold air on the valley floors, and with no incoming weather systems to stir up the atmosphere, those inversions are likely to persist for the foreseeable future. That also means there’s no snow in the forecast for the next 10 days unless there’s a dramatic shift in the jet stream, which will stay far to the north for the next week at least. Continue reading

New coral data traces 7,000 years of El Niño history

20th century oscillations show intensification that may be linked with global warming

El Nino graphic

A NOAA graphic showing early January 2012 ocean surface temperature anomalies.

By Summit Voice

SUMMIT COUNTY — Atmospheric scientists say they’ve used coral records to trace the history of El Niño cycles going back about 7.000 years, showing that 20th century oscillations  are much stronger than those captured in the fossil record.

But the study also showed large natural variations in past ENSO strength, making it difficult to attribute the 20th century intensification of ENSO to rising carbon dioxide levels. Such large natural fluctuations in ENSO activity are also apparent in multi-century climate model simulations, but the 20th century intensification stands out as statistically significant and could be linked with global warming.

The new information will help assess the accuracy of climate model projections for 21st century climate change in the tropical Pacific. Continue reading

Colorado: Mostly dry into December

Is Colorado facing more drought?

So far, the pattern of storms across the Pacific Northwest and northern Rockies shows little signs of changing, with most of the weather action far north of Colorado.

By Bob Berwyn

FRISCO — Ullr, why has thou forsaken us?

If you’re holding out for more snow before heading out to make turns on the hill, you may want to reconsider. The outlook for the next 10 days is mostly dry and warm, with perhaps a chance of snow brushing the northern mountains Sunday night into Monday morning. Beyond that, another ridge will build into the Southwest, bringing more dry weather and a return to above normal temps for much of next week. Continue reading

Climate: Parts of the tropical Pacific Ocean are shifting toward a permanent El Niño-like pattern

Archived ocean observations help create new data set for climate models

Atmospheric circulation patterns drive convection in the tropics and can have a far-reaching effect on global climate. Bob Berwyn photo.

By Summit Voice

SUMMIT COUNTY — A new set of more complete sea surface temperature data has helped scientists explain a gradual, decades-long slowdown of a key tropical atmospheric circulation, linking it with the steady increase in global temperatures during the past few decades.

“Our experiments show that the main driver of the change in the Walker circulation is the gradual change that has taken place in the surface temperature pattern toward a more El Niño-like state,” said Hiroki Tokinaga, associate researcher at the International Pacific Research Center, University of Hawaii at Manoa. “We don’t have enough data yet to say to what degree the slowdown over the last 60 years is due to a rise in man-made greenhouse gases or to natural cycles in the climate,” Tokinaga said.

The Walker circulation determines much of the tropical Indo-Pacific climate and has a global impact as seen in the floods and droughts spawned by the El Niño-Southern Oscillation. Meteorological observations over the last 60 years show this atmospheric circulation has slowed: the trade winds have weakened and rainfall has shifted eastward toward the central Pacific. Continue reading

Climate: NOAA drops El Niño watch

Forecasters call for neutral conditions, but say a La Niña is not out of the question

n El Niño never managed to establish itself in the equatorial Pacific this year.

The three-month precipitation outlook from NOAA’s Climate Prediction Center.

By Summit Voice

FRISCO — With sea surface temps cooling to near average in much of the equatorial Pacific, NOAA’s Climate Prediction Center has dropped an El Niño watch that’s been in effect for the past several months.

El Niño is part of a cyclical pattern of sea surface temperature variations that affects global weather patterns. The emerging El Niño forecast last spring and summer offered some hope for drought relief in the parched Southwest and the southern tier of states, where warmer than average Pacific Ocean temps can help boost winter and spring precipitation.

During La Niña years, when cooler-than-average sea surface temperatures prevail in the same region, the storm track often shifts northward, driving storms into the Pacific Northwest and then down across the northern Rockies and northwest Colorado. Continue reading

Follow

Get every new post delivered to your Inbox.

Join 7,757 other followers