Our Climate

Climate of the Earth: Climate (from ancient Greek: κλίμα, "Clime") is commonly defined as the weather averaged over a long period of time. The classical period is 30 years, as defined by the World Meteorological Organization.
 
Over historic time spans there are a number of static variables that determine climate, including: latitude, altitude, proportion of land to water, and proximity to oceans and mountains. Other climate determinants are more dynamic: The thermohaline circulation of the ocean distributes heat energy between the equatorial and polar regions; other ocean currents do the same between land and water on a more regional scale. Degree of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level. Alterations in the quantity of atmospheric greenhouse gases determines the amount of solar energy retained by the planet, leading to global warming or global cooling. The variables which determine climate are numerous and the interactions complex, but there is general agreement that the broad outlines are understood, at least insofar as the determinants of historical climate change are concerned.
 
 cientists use climate indices in their attempt to characterize and understand the various climate mechanisms that culminate in our daily weather. Climate indices are used to represent the essential elements of climate. Those are generally devised with the twin objectives of simplicity and completeness, and each index typically represents the status and timing of the climate factor it represents. By their very nature, indices are simple, and combine many details into a generalized, overall description of the atmosphere or ocean which can be used to characterize the factors which impact the global climate system.
 

Role of Oceans in Climate: 
From the dawn of time, people have suspected powerful forces lurking deep in the oceans ‚ from the Greeks' fearsome sea-god Neptune to John Wyndham's submarine aliens in his 1950s novel The Kraken Wakes. But science is once again going one better than science fiction. Researchers are discovering that hidden 'rivers' run through the oceans, and these powerful currents hold the destiny of our planet's climate. It's a reminder that "weather" is not just a matter of the Sun's heat affecting the Earth's atmosphere. The world's interconnected oceans can store up solar heat in one part of the globe in one season, and invisible rivers in the ocean can transport the warmth thousands of kilometres to another part of the globe and deliver it in another season. In the case of the North Atlantic, heat is carried northward and eastward by the Gulf Stream. This current warms the coast evenly through the year, in winter as well as summer. Averaged over a year, the Gulf Stream provides Western Europe with a third as much warmth as the Sun does.The warm water that is so important to Europe actually comes from the other side of the world, in the Pacific Ocean. This tepid stream, flowing unseen through the oceans, is the longest river in the world. It flows along the surface, both because it is warm (and warm water, like warm air, rises) and because it is less salty ‚ and so less dense - than the deeper water. The warm waters travel westward from the central Pacific, past the north coast of Australia and round the southern tip of Africa before moving up into the Atlantic.Around the latitude of Iceland, the moving stream becomes so dense that it sinks into the depths.

This stream now becomes a cold river, flowing back along the ocean floor. Rounding the south of Africa and Australia, it returns to the Pacific, where it is pushed to the surface and warms to complete the cycle. The whole effect is like a conveyor belt bringing Pacific warmth to the North Atlantic.
The ocean conveyor belt has run more or less smoothly since the end of the last Ice Age. But global warming may now throw a spanner into its workings. The planet is undoubtedly warming up, even if people still argue about how much of this is due to human activities, and the extra heat is melting ice in the Arctic Ocean. The ice turns into fresh water, which flows into the salty North Atlantic.
The danger is that this fresh water might dilute the salty current of the Gulf Stream so much that it stops sinking down into the ocean depths near Iceland. If the Gulf Stream does stop, there will be nothing pushing the deep cold river at the bottom of the North Atlantic. As the Atlantic portion of the ocean conveyor belt grinds to a halt, then Europe could indeed freeze ‚ ironically, as a direct result of global warming. Global warming may interfere with not just the North Atlantic currents, but may disrupt the entire system of ocean currents ‚ affecting the entire world's weather.

 
 
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