Posts Tagged ‘North Atlantic Oscillation’

Little Ice Age could well have resulted from reduced solar activity

October 4, 2013

This paper is particularly interesting because the senior author, Thomas Stocker, is the Vice-Chair of the IPCC and presented the summary of AR5 at the Press Conference last week!!

It is very strange then that the IPCC is so nonchalant about solar effects. In any event whatever the various climate models say, the Landscheidt Minimum is here and global cooling will continue for the next two decades or so. As The Register puts it.
” There’s been criticism for the Intergovernmental Panel on Climate Change (IPCC) over its latest AR5 report from many quarters for many reasons. But today there’s new research focusing on one particular aspect of that criticism.The particular part of the IPCC’s science in question is its accounting for the effects of changes in the Sun on the climate of planet Earth. Many climatologists have long sought to suggest that the effects of solar variability are minor, certainly when compared to those of human-driven CO2 emissions. Others, however, while admitting that the Sun changes only a very little over human timescales, think that it might be an important factor. This matters because solar physicists think that the Sun is about to enter a “grand minimum”, a prolonged period of low activity. 
The current 11-year peak in solar action is the weakest seen for a long time, and it may presage a lengthy quiet period. Previously, historical records suggest that such periods have been accompanied by chilly conditions on Earth – perhaps to the point where a coming minimum might counteract or even render irrelevant humanity’s carbon emissions. The “Little Ice Age” seen from the 15th to the 19th centuries is often mentioned in this context.
Lehner, Flavio, Andreas Born, Christoph C. Raible, Thomas F. Stocker, 2013: Amplified Inception of European Little Ice Age by Sea Ice–Ocean–Atmosphere Feedbacks.  J. Climate26, 7586–7602.
doi: http://dx.doi.org/10.1175/JCLI-D-12-00690.1
The University of Berne press release writes:
The study that was realized at the OCCR shows that volcanic eruptions and reduced solar radiation caused global cooling between the thirteenth and the fifteenth centuries. The resulting accelerated formation of sea ice in the Northern Seas triggered a positive feedback process that shaped the Little Ice Age. The winter weather in Europe is largely governed by the so-called North Atlantic Oscillation (NAO). ……. Until now, the NAO was believed to be jointly responsible for the cooling in the early fifteenth century along with volcanic eruptions and weakened solar radiation. The subsequent Little Ice Age continued into the nineteenth century. Now, however, Bernese climate researchers Flavio Lehner, Andreas Born, Christoph Raible and Thomas Stocker reveal that the Little Ice Age was also able to take its course without the influence of the NAO, driven purely by the consequences of strong and frequent volcanic eruptions at the time, a reduced solar radiation, or both together.
Using simulations on the CSCS supercomputer “Monte Rosa”, the climate researchers searched for a feedback process that was capable of triggering the Little Ice Age.
….. For the scientists, the fact that all the slightly altered, realistic simulations and the synthetic ice simulation yielded consistent results is solid proof that the Little Ice Age was primarily governed by external triggers. Volcanic activity and less solar radiation initially caused an increase in sea-ice formation independently of atmospheric circulation. Due to the cooling, the mean sea level pressure gradually increased over the Barents Sea, which enabled the cold air to reach Europe. “However, this pressure response is clearly a delayed reaction of the atmosphere to the preceding processes in the ocean,” says Raible.
Abstract: The inception of the Little Ice Age (~1400–1700 AD) is believed to have been driven by an interplay of external forcing and climate system internal variability. While the hemispheric signal seems to have been dominated by solar irradiance and volcanic eruptions, the understanding of mechanisms shaping the climate on a continental scale is less robust. In an ensemble of transient model simulations and a new type of sensitivity experiments with artificial sea ice growth, the authors identify a sea ice–ocean–atmosphere feedback mechanism that amplifies the Little Ice Age cooling in the North Atlantic–European region and produces the temperature pattern suggested by paleoclimatic reconstructions. Initiated by increasing negative forcing, the Arctic sea ice substantially expands at the beginning of the Little Ice Age. The excess of sea ice is exported to the subpolar North Atlantic, where it melts, thereby weakening convection of the ocean. Consequently, northward ocean heat transport is reduced, reinforcing the expansion of the sea ice and the cooling of the Northern Hemisphere. In the Nordic Seas, sea surface height anomalies cause the oceanic recirculation to strengthen at the expense of the warm Barents Sea inflow, thereby further reinforcing sea ice growth. The absent ocean–atmosphere heat flux in the Barents Sea results in an amplified cooling over Northern Europe. The positive nature of this feedback mechanism enables sea ice to remain in an expanded state for decades up to a century, favoring sustained cold periods over Europe such as the Little Ice Age. Support for the feedback mechanism comes from recent proxy reconstructions around the Nordic Seas

2010 was coldest year in Sweden in 23 years and coldest in Norway since 1941

March 8, 2011

The 2010 winter cold can be coupled to the NAO and to large blocking high pressure areas: image smhi

My actual experiences during 2010 (in Asia and in Northern Europe) and my very real electricity bills are far more compelling than fudged statistics and Hockey Stick Illusions from the global warming alarmists. The reality is that we are in for 2 or 3 decades of cooling courtesy of the sun and man-made carbon dioxide is of little consequence. The sun drives the ocean currents and the North Atlantic Oscillation was negative as it was for the 2009/10 winter.

The global warming / carbon dioxide scare is driven not only by carbon trading scams and catastrophe promoting insurance companies but also by so-called climate scientists who have lost the scepticism that is at the heart of science and developed a Nostradamus complex.

From Stockholm News:

Most people who live in Sweden most certainly remember some really cold months last year, particularly the winter months of January, February and December. There was for certain a serious heat wave in July. But that did not help out: 2010 was the coldest year in Sweden in 23 years.

The Swedish Weather Agency’s preliminary estimations show that Sweden as a whole had around one degree Celsius below normal temperatures last year.

Since 1987, all years have been warmer than normal, except in 1996, which had a small temperature deficit. “Normal” in this context is the average for the years 1961-1990.

The coldest part of the country was in the west, and consequently the western neighbouring country of Norway also had a cold last year. Their general temperature was likewise one degree Celsius below normal. This made last year the coldest in Norway since 1941 and the tenth coldest year since 1900, writes the Norwegian Meteorological Institute.


La Niña and NAO driving current stormy weather

February 8, 2011
During cold La Niña episodes the normal patter...

La Nina Regional impacts: Image via Wikipedia

It may seem obvious (or it should be) that it is ocean currents that dominate weather and man-made effects pale into insignificance in relation to these. But it has been more politically correct to find that every kind of weather event is due to man-made global warming.

But as this article in PhysOrg shows, perhaps the oceans (and the sun) are beginning to get their due (but of course they don’t really care whether anybody believes in them or not – they just carry on).

The term La Niña refers to a period of cooler-than-average sea-surface temperatures in the Equatorial Pacific Ocean that occurs as part of natural climate variability. This situation is roughly the opposite of what happens during El Niño (“the boy”) events, when surface waters in this region are warmer than normal. Because the Pacific is the largest ocean on the planet, any significant changes in average conditions there can have consequences for temperature, rainfall and vegetation in distant places. Scientists at the International Research Institute for Climate and Society (IRI), part of Columbia’s Earth Institute, expect moderate-to-strong La Niña conditions to continue in the tropical Pacific, potentially causing additional shifts in rainfall patterns across many parts of the world in months to come.

These shifts, combined with socioeconomic conditions and other factors, are making some countries more vulnerable. However, La Niña and El Niño conditions actually allow for more accurate seasonal forecasts and help better predict extreme drought or rainfall in some areas. ………..

“Based on current observations and on predictions from models, we see at least a 90 percent chance that La Niña conditions will continue through March,” said IRI’s chief forecaster, Tony Barnston.

Climate scientists have found La Niña’s fingerprints on a number of extreme weather events such as the devastating flood that occurred in Pakistan in 2010, as well as flooding in West Africa, South Africa and most recently in Queensland, Australia, where an area equal to the combined size of France and Germany was underwater. La Niña is also to blame for Cyclone Yasi, one of the strongest to hit Australia, which came ashore on Feb. 2. Cyclone Yasi is the second most damaging Australian cyclone on record after Cyclone Tracy, which struck in 1974.

But La Niña isn’t to blame for the recent severe weather affecting the Northeast. Winter weather for these regions is often driven not by La Niña but by large-scale weather patterns over the U.S., the northern Atlantic Ocean and the Arctic. These are often short-term, and are generally predictable only a week or so in advance. They are the culprits responsible for the dip in temperatures and spike in snow storms in the Midwest and Northeast.

…………

Since 1950, the world has experienced six major La Niña events, wreaking havoc in countries around the world. In 2000, for example, floods associated with La Niña affected 400,000 people in southern Africa, caused at least 96 deaths and left 32,000 homeless.

La Niña conditions typically persist for 9 to 12 months, peaking sometime during the end of the year. But 2010 was a lively year for climate scientists: For the first four months of this year, El Niño conditions prevailed in the tropical Pacific, but that quickly changed, and by June, a La Niña pattern had emerged.

“Last year’s transition from El Niño to La Niña was about the most sudden we’ve ever had,” Barnston said. “When we had rapid flips like this in the past, we sometimes ended up having a two-year La Niña, such as right after the El Niño episodes of 1972 to 1973 and 1997 to 1998.”

Barnston cautions that the likelihood of this happening with the current La Niña is unknown. “Even if we do have a second year of La Niña developing in northern summer 2011, we expect at least a brief return to neutral conditions from May to July of 2011.”

Related:

https://ktwop.wordpress.com/2011/02/03/la-nina-begins-to-show-up-in-global-temperature/

https://ktwop.wordpress.com/2011/02/05/la-nina-will-last-well-into-2011-and-could-extend-into-2012/

https://ktwop.wordpress.com/tag/la-nina/


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