Global warming and atmospheric circulation

According to a study conducted in 2006 by Gabriel Vecchi of the University Corporation for Atmospheric Research, the trade winds in the Pacific Ocean are weakening as a result of global warming. This conclusion is based on the findings of a study that showed the biology in the area may be changing, which could be harmful to marine life and have the long-term effect of disrupting the marine food chain. Researchers predict that it could also reduce the biological productivity of the Pacific Ocean, which could have an impact on not only the natural ecosystem and balance, but also the food supply for millions of people.

The study used climate data consisting of sea-level atmospheric pressure over the past 150 years and combined that with computer

Much of the world's population depends on fish as a food source. Not only El Niño, but also global warming and climate change have negative effects on marine life. (NOAA, Fisheries Collection)

modeling to conclude that the wind has weakened by about 3.5 percent since the mid-1800s. The researchers predict another 10 percent decrease is possible by the end of the 21st century.

Some of the computer modeling simulations included variables such as the effects of human greenhouse gas emissions, while other simulations included only natural factors that affect climate such as volcanic eruptions and solar variations. Vecchi concluded that the observed weakening of the trade winds could only be accounted for through the model that included human activity—specifically from greenhouse gases and the burning of fossil fuels. According to an interview on the LiveScience Web site, Vecchi believes "this is evidence supporting global warming and also evidence of our ability to make reasonable predictions of at least the large scale changes that we should expect from global warming."

Vecchi believes global warming is to blame because in order for the ocean and atmosphere to maintain an energy balance, the rate that the atmosphere absorbs water from the ocean must equal the amount that it loses to rainfall. As global warming increases the air temperature, more water evaporates from the ocean into the air. The atmosphere cannot convert it to rainfall and return it back fast enough. Because the air is gaining water faster than it can release it, it gets overloaded and the natural system compensates by slowing the trade winds down, decreasing the amount of water being drawn up into the atmosphere, in order to maintain the energy balance.

El Niño was named by Peruvian fishermen who first noticed a warm current that appeared off the coast of South America at the beginning of the calendar year during the Christmas season. El Niño literally means the "little boy" or the "Christ child" in Spanish.

It was not until the 1960s that El Niño was recognized as a global phenomenon that effected changes over the entire Pacific. Today, it is studied and recognized as a physical process with a huge influence on the climatic conditions over large areas of the world.

The name El Niño refers to the warm phase of a larger oscillation in which the surface temperature of the central and eastern part of the tropical Pacific varies up to 6.7°F (4°C) and is associated with changes in the winds and rainfall patterns. The complete, larger phenomenon is called the El Niño-Southern Oscillation (ENSO). The warm El Niño phase lasts for eight to 10 months. The entire ENSO cycle lasts about three to seven years. The Pacific Ocean signatures are important temperature fluctuations in surface waters of the tropical eastern Pacific Ocean. ENSO is associated with floods, droughts, and other climatic disturbances. ENSO has signatures in the Pacific, Atlantic, and Indian Oceans. While it is a natural part of the Earth's climate, scientists today are concerned about whether or not its intensity or frequency may change as a result of global warming. The first official description of ENSO in terms of its physical properties and behaviors was by Dr. Jacob Bjerknes of the University of California, Los Angeles, in 1969.

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