Guyana's low-elevation coast hosts the majority of its population. It is predicted to become one of the world's top 10 most impacted nations from sea level rise in terms of the percentage of the population and extent of urban area implicated. Ranging from a low estimate of 16 percent to a high estimate of 103 percent, Guyana is expected to have one of the greatest losses in gross domestic product in the Caribbean as a result of climate change. One of the poorest countries in the western hemisphere, Guyana remains reliant on foreign assistance to mitigate potential consequences. Researchers have demonstrated an urgent need to update flood control. Irrigation technologies also need rehabilitation. The name Guyana is Amerindian for "Land of Water," but the country may be losing its fresh groundwater. It has been suggested that this may contribute to coastal subsidence.

The capital city Georgetown is located along Guyana's 270-mi. (434 km.) coast. Three quarters of the national population of 765,000 lives within 20 mi. (32 km.) of the sea. This same area hosts most agricultural production. Drainage is a major problem, and agricultural irrigation systems must control seawater intrusion. The centerpiece of the outdated drainage and irrigation infrastructure is the East Demerara Water Conservancy (EDWC) Dam. This structure was developed in 1880 and holds a volume of more than 100 sq. mi. (259 sq. km.) of water, but it is currently believed to over-top and seep. Defective intake contributes to dry season water shortages.

Sea level rise in Guyana is believed to be two to five times higher than global averages. It was measured at an excess of 0.3 in. (10 mm.) annually 1951-79. Research suggests that this trend has continued. Major floods in 2005 and 2006 demonstrated an inability to clear water. The impact of the flood in 2005 has been estimated at 60 percent of GDP. Many biodiverse eco systems exist in Guyana, including mangroves in low-lying areas. Guyana hosts an extensive tropical forest that makes up a northern portion of the Amazon rainforest. In 2000, forests covered over 70 percent of the country, but multinational timber and mining concessions have accelerated deforestation.

Guyana ratified the United Nations Convention on Climate Change in 1994 and the Kyoto Protocol in 2003. The country has compiled an extensive climate change action plan. It is part of the Caribbean Planning for Adaptation to Global Climate Change Project. Georgetown hosts the administrative headquarters of the Caribbean Community (CARICOM). CARICOM is involved in climate change vulnerability assessments and adaptation programs.

As many countries in the region, including Guyana, rely heavily on fossil fuel, CARICOM oversees research on alternative energy. A bagasse cogenera-tion project is the first initiative in the nation under review for support from the Clean Development Mechanism.

SEE ALSO: Floods; Salinity; Sea Level, Rising.

BIBLIOGRAPHY. Susmita Dasgupta, et al., The Impact of Sea Level Rise on Developing Countries: A Comparative Analysis (World Bank, 2007); Global Environmental Facility, Conservancy Adaptation Project Information Document (GEF, 2006); Walter Vergara, Adapting to Climate Change (World Bank, 2005).

Mary Finley-Brook University of Richmond

Hadley, George (1685-1768)

GEORGE HADLEY was an English lawyer, physicist, and meteorologist who first accurately theorized a hypothesis for the trade winds and the associated north-south circulation pattern now known as the Hadley Cell. This piece of information was particularly important in Hadley's times, as it helped the journeys of English vessels toward North American shores. Hadley was intrigued that winds that should have blown northward had, instead, a western course.

Hadley was born on February 12, 1685, in London, England to Katherine FitzJames and George Hadley. He was part of a family of six children and his father was the high sheriff of Hertfordshire. George was initially overshadowed by the fame of his brother John, the inventor of the octant. He studied law, but soon found out that he preferred physics to legal work. For 7 years he was in charge of the meteorological observations for the Royal Society.

Yet, his fame rests on his work of the 1730s, when Hadley was able to complete Edmond Halley's theory of trade winds. Halley had failed to explain completely the westward component of the trades. In his famous paper "Concerning the Cause of the General Trade Winds," published in 1735, Hadley related the direction of trade winds to the rotation of the Earth.

The meteorologist started from the well-known fact that air at the equator is heated more strongly than at any other place on Earth. Air above the poles is cooler than at any other location. Therefore, it is speculated that surface air near the equator will ascend into the upper atmosphere and, above the poles, descend from the upper atmosphere to ground level. In order to balance these vertical movements of air, Hadley also assumed that air flows across the Earth's surface from each pole back to the equator and, in the upper atmosphere, from above the equator to above the poles.

This movement of air is called a convection cell, where convection describes the transfer of heat carried by a moving fluid. Yet, Hadley knew that his model was too simplified to explain the motion of the winds, which obviously do not blow from north to south in the Northern Hemisphere and from south to north in the Southern Hemisphere. He then explained that winds actually tend to blow from the east or west because of Earth's rotation.

The movement of the planet causes airflows that would otherwise be from the north or south to be diverted to the east or west. Because of his fame, Hadley was elected a Royal Fellow in 1745. He died on June 28, 1768.

A century after Hadley first proposed his theory, the French physicist Gaspard Gustave de Coriolis

Hadley Circulation provides westward windflow at the Earth's surface and eastward jet streams at higher altitudes. The circulating air patterns create convection currents in four global locations—each current is called a Hadley cell.

devised a mathematical description detailing how an object, in motion on a rotating body, follows a curved path in relation to any other body on the same rotating body.

SEE ALSO: Coriolis Force; Wind-Driven Circulation; Winds, Easterlies; Winds, Westerlies.

BIBLIOGRAPHY. H.F. Diaz and R.S. Bradley, eds., The Hadley Circulation: Past, Present and Future (Kluwer Academic Publishers, 2004); S. George Philander, Is the Temperature Rising? The Uncertain Science of Global Warming (Princeton University Press, 1998).

Luca Prono University of Nottingham

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