Climate Impacts Discussion: What economic impacts does ENSO have? What can we say about ENSO and global climate change? Are there other phenomena similar to ENSO? Can we predict ENSO?

General Circulation The surface pressure Northern Winter (January) High over Land, Low over Ocean

What is the North Atlantic Oscillation ? " A sea saw of atmospheric mass which alternates between the polar and subtropical regions. " Changes in the mass and pressure fields lead to variability in the strength and pathway of storm systems crossing the Atlantic from the US East coast to Europe. " The NAO is most noticeable during the winter season (November - April) with maximum amplitude and persistence in the Atlantic sector.

The North Atlantic Oscillation Index " An Index can be constructed that represents the phase of the NAO. Most commonly the NAO index is based on the surface pressure (SLP) difference between the Subtropical (Azores) high and the Subpolar (Island) low. " Very often the pressure readings from two stations one on Iceland and the other either the Azores, Lisbon or Gibraltar are used to construct the NAO index. The twice daily reading are averaged from November through March and the difference in then the winter NAO index.

The North Atlantic Oscillation Index " The NAO index shows large variations from year to year. This interannual signal was especially strong during the end of the 19 th century. " Sometimes the NAO index stays in one phase phase for several years in a row. This decadal variability was quite strong at the beginning and end of the 20 th century. " One might also interpret the recent 30 years as a trend in the NAO index possibly linked to "global warming".

The positive NAO index phase " The positive NAO index phase shows a stronger than usual subtropical high pressure center and a deep than normal Icelandic low. " The increased pressure difference results in more and stronger winter storms crossing the Atlantic Ocean on a more northerly track. " This results in warm and wet winters in Europe and in cold and dry winters in northern Canada and Greenland. " The eastern US experiences mild and wet winter conditions.

The negative NAO index phase " The negative NAO index phase shows a weak subtropical high and weak Icelandic low. " The reduced pressure gradient results in fewer and weaker winter storms crossing on a more west-east pathway. " They bring moist air into the Mediterranean and cold weather to northern Europe. " The US east cost experiences more cold air outbreaks and hence snowy winter conditions. " Greenland, however, will have milder winter temperatures.

Impacts of the NAO.

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Us East Coast Impacts of the NAO " The US East coast experiences milder winter conditions during a positive NAO index phase. " The amount of snow cover is reduced. " Warmer than usual ocean temperatures cause more frequent occurrence of "red tides" in the summer. " Colder than usual tropical ocean temperatures reduce the number of hurricanes in the following summer. " Cold ocean temperatures in the spawning grounds over the Grand Banks cause less cod reproduction.

Impacts of the NAO in Europe " Northern Europe experiences mild and wet winter during the positive NAO index phase. " This has dramatic consequences for hydro-electric power generation and heating oil consumption. " South-Eastern Europe receives less rain and hence causes significant problems with drinking water supply and reduced stream flow volume in the Middle East. " Harvest yield of grapes and olives have been shown to depend significantly on the NAO.

NAO and Energy in Norway " Norway experience cold winters during a negative NAO phase. " Heating Oil consumption in Norway varies by 30% in good (anti) correlation with the NAO. " Correlation with precipitation results in variability in hydropower generation.

NAO and Energy in Norway Norway gets 99% of its electricity from hydropower Sweden get 50% from hydropower, 50% from nuclear energy What happens if the rain fall varies?

NAO and Energy in Norway In Norway export and import of energy is relatively new. An open trade market has been established (Nord Pool) How will the price change with climate change?

NAO and Energy in Norway There is an amazing correlation between the price of energy and water reservoir level which varies due to changes in rain fall.

NAO and Water Resources in Turkey and the Middle East Precipitation in Turkey is well correlated with the NAO. As a result spring stream flow in the Euphrates River varies by about 50% with the NAO. An upward trend in the NAO will lead to drought conditions in the Middle East.

Climate and Society " Precipitation " Temperature " CO2 and other gases " Energy " Food " Health " Population dynamics