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Monday, 21 February, 2000, 19:23 GMT
Date set for desert Earth
By BBC News Online's Damian Carrington in Washington DC
The Earth is entering the final 10% of its lifespan, according to a US geoscientist.
"The Sun, like all main sequence stars, is getting brighter with time and eventually temperatures will become high enough so that the oceans evaporate," said Professor Kasting. At 60 degrees Celsius (140 degrees Fahrenheit), water becomes a major constituent of the atmosphere. Much of this water drifts up to the stratosphere and is lost into space. Eventually, all the oceans will leak out of the Earth's grasp. Burnt-out planet "Astronomers always knew that the oceans would evaporate, but they typically thought it would occur only when the Sun left the main sequence - that will be in five billion years."
"However, my calculations show the oceans may evaporate much earlier," said Professor Kasting. "They are somewhat pessimistic and present a worst-case scenario, but they say a billion years." The earlier loss of carbon dioxide will occur because as the climate gets hotter and wetter, more rock is weathered by rain. This dissolves carbon dioxide and hides it away on the ocean floor as calcium carbonate. "Obviously, a billion, even a half billion years, is a long way off in the future," said Professor Kasting. "But these models can help us refine our understanding of the time that a planet remains in an orbit where life can exist." "If we calculated correctly, Earth has been habitable for 4.5 billion years and only has a half billion years left." Professor Kasting's comments were made at the annual meeting of the American Association for the Advancement of Science. |
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20 Feb 00 | Washington 2000
08 Sep 99 | Science/Nature
04 Oct 99 | Science/Nature
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