As long as there are
ice sheets anywhere in the world, the
Earth may be said to be in an ice age, even though we are enjoying a comparatively
warm inter-glacial period. Great sheets of ice cover most of Antarctica and Greenland. If all that ice were melted, the resulting water would raise sea-level by some eighty metres, enough to flood most of the world’s major cities.
The variations of climate have been growing more extreme and rapid in their oscillations. Recent work has shown that fluctuations between warm and cold conditions have occurred with astonishing swiftness. About 43,000 years
ago, there was a short-lived interlude of 2,000 or 3,000 years when summer temperatures were as high as they are now. The sudden warming of some 43,000 years ago was remarkable for the rapidity of its occurrence. A similar sudden pulse of warmer climate occurred more recently – about 12,500 years ago. The emergence from cold to warm conditions took only a few decades.
When all sources of reflection (snow, clouds, ice, deserts and land) are added together, our planet turns back into space some 36% of the solar
radiation falling on it. But the earth has some features which compensates for the energy loss caused by the reflectionof sunlight. The earth is not a totally efficient
heat radiator. The atmospheric gases generate two radiation
traps – one due to water vapor and the other due to carbon dioxide. The effect of the traps is to reduce the radiating efficiency of the earth’s surface. The surface of the earth cannot cool itself as efficiently. The heat-radiation traps in the lower atmosphere are known as the “greenhouse effect”.
Of the heat radiated from the earth’s surface, about one-third escapes into space and the other two-thirds are reabsorbed. However, evaporation of water at the ocean surface cools the ocean. The earth functions as an efficient heat engine. If the heat transfer (from hot to cool regions) were somehow reduced, the tropics would retain more heat than they have now, making the development of ice domes on tropical mountains unlikely. Only if the amount of carbon dioxide were enormously increased would the trap widen its influence significantly.
More abstracts about the Ice