Featured Research

from universities, journals, and other organizations

Earth's Oceans Destined To Leave In Billion Years

Date:
February 23, 2000
Source:
Penn State
Summary:
The Earth's oceans will disappear in about one billion years due to increased temperatures from a maturing sun, but Earth's problems may begin in half that time because of falling levels of carbon dioxide in the atmosphere, according to a Penn State researcher.

Washington, D.C. -- The Earth's oceans will disappear in about one billion years due to increased temperatures from a maturing sun, but Earth's problems may begin in half that time because of falling levels of carbon dioxide in the atmosphere, according to a Penn State researcher.

"The sun, like all main sequence stars, is getting brighter with time and that affects the Earth's climate," says Dr. James F. Kasting, professor of meteorology and geosciences. "Eventually temperatures will become high enough so that the oceans evaporate."

At 140 degrees Fahrenheit, water becomes a major constituent of the atmosphere. Much of this water migrates to the stratosphere where it is lost to the vacuum. Eventually, the oceans will evaporate into space.

"Astronomers always knew that the oceans would evaporate, but they typically thought it would occur only when the sun left the main sequence," Kasting told attendees today (Feb. 20) at the annual meeting of the American Association for the Advancement of Science. "That will be in 5 billion years."

Stars leave the main sequence when they stop burning hydrogen. The sun, a yellow, G-2 star, will then become a red giant encompassing the orbit of Mercury. Mercury will disappear and Venus will lose its atmosphere and become a burnt out planet. The Earth will suffer the same fate, even though it is outside the red giant's immediate reach.

"However, the oceans may evaporate much earlier," says Kasting, a faculty member with the College of Earth and Mineral Sciences. "My calculations are somewhat pessimistic and present a worst case scenario that does not include the effects of clouds, but they say a billion years."

This model was developed with Ken Caldeira, now at Lawrence Livermore Laboratory.

Things may go bad long before the Earth is a waterless desert. As the climate becomes warmer, the cycle of silicate rock weathering speeds up. This cycle removes carbon dioxide from the atmosphere and sequesters it in the oceans as calcium carbonate.

"The silicate weathering cycle stabilizes the Earth's climate for a time," says Kasting. "Eventually, atmospheric carbon dioxide levels will become so low that it will not be able to do so, but before then, there will not be sufficient carbon dioxide to sustain most plants."

Plants use carbon dioxide in photosynthesis to convert the sun's energy to sugars and other carbohydrates. Two main kinds of photosynthesis exist, C3 and C4. In a half billion years, the models predict that carbon dioxide will be at the compensation point for C3 plants which make up 95 percent of all plants. Below the compensation point, carbon dioxide is not concentrated enough for these plants to photosynthesize. C3 plants include trees and most crops.

C4 plants, which include corn, sugar cane and other tropical grasses, can still photosynthesize because they have an internal mechanism to concentrate carbon dioxide, but these plants cannot sustain the biosphere as we know it today.

"If carbon dioxide levels in the atmosphere continue to increase over the next few centuries, they could remain high for a very long time," says Kasting. "Then, after fossil fuels run out, it would take a million years or so for levels to return to present."

But even if there is a pulse of high carbon dioxide in the near future, by a half billion years, levels will be too low for productive plant life.

"Obviously, a billion, even a half billion years, are a long way off in the future," says Kasting. "However, these models can help us refine our understanding of the time that a planet remains in an orbit where life can exist."

Only a narrow spherical shell of space exists at a distance from a star that is neither too cold nor too warm for life. As a sun matures and brightens, that spherical shell moves outward. A planet must remain in the livable shell for long enough for life to evolve, even while that band moves outward. If planets lose their water supply, a mandatory requirement for life, earlier than previously thought, then that creates a shorter window for livable planets.

"If we calculated correctly, Earth has been habitable for 4.5 billion years and only has a half billion years left," says Kasting.


Story Source:

The above story is based on materials provided by Penn State. Note: Materials may be edited for content and length.


Cite This Page:

Penn State. "Earth's Oceans Destined To Leave In Billion Years." ScienceDaily. ScienceDaily, 23 February 2000. <www.sciencedaily.com/releases/2000/02/000223071739.htm>.
Penn State. (2000, February 23). Earth's Oceans Destined To Leave In Billion Years. ScienceDaily. Retrieved July 30, 2014 from www.sciencedaily.com/releases/2000/02/000223071739.htm
Penn State. "Earth's Oceans Destined To Leave In Billion Years." ScienceDaily. www.sciencedaily.com/releases/2000/02/000223071739.htm (accessed July 30, 2014).

Share This




More Earth & Climate News

Wednesday, July 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Climate Change Could Cost Billions, According To White House

Climate Change Could Cost Billions, According To White House

Newsy (July 29, 2014) A report from the White House warns not curbing greenhouse gas emissions could cost the U.S. billions. Video provided by Newsy
Powered by NewsLook.com
Climate Change Could Cost Billions According To White House

Climate Change Could Cost Billions According To White House

Newsy (July 29, 2014) A report from the White House warns not curbing greenhouse gas emissions could cost the U.S. billions. Video provided by Newsy
Powered by NewsLook.com
Jane Goodall Warns Great Apes Face Extinction

Jane Goodall Warns Great Apes Face Extinction

AFP (July 29, 2014) The world's great apes face extinction within decades, renowned chimpanzee expert Jane Goodall warned Tuesday in a call to arms to ensure man's closest relatives are not wiped out. Duration: 00:58 Video provided by AFP
Powered by NewsLook.com
Rat Infestation at Paris' Tuileries Garden

Rat Infestation at Paris' Tuileries Garden

AFP (July 29, 2014) An infestation of rats is causing concern among tourists at Paris' most famous park -- the Tuileries garden next to the Louvre Museum. Duration: 00:54 Video provided by AFP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins