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article imageLife on Earth: Gone in a billion years for want of carbon dioxide

By Robert Myles     Jul 2, 2013 in Science
Saint Andrews - But the bad news for any man-made global warming skeptics is: it won’t happen tomorrow, or next year or even next millennium.
The (very) long range global warming forecast was given by Jack O’Malley James, PhD, and an astro-biologist at the University of St. Andrews in Scotland presenting a research paper this week to the 2013 National Astronomy Meeting of the UK’s Royal Astronomical Society.
It’s only taken 150 years, give or take a decade or two, since the Industrial Revolution first gave impetus to increasing levels of carbon dioxide in Earth’s atmosphere. For now, the focus is on how to curb carbon emissions but a billion or so years down the line, the problem for life on Earth may be not too much, but, rather, too little CO2 in Earth’s atmosphere to sustain life.
O'Malley-James postulates that within the next billion years or so, increased evaporation rates and chemical reactions with rainwater will increasingly reduce the amount of carbon dioxide in Earth’s atmosphere. Declining CO2 levels will have the knock-on effect of causing the disappearance of plants and animals, with Earth’s principal life-form being microbial life. Depletion of plant life will cause oxygen depletion and as if that weren’t enough, rising temperatures will start causing the oceans to evaporate. Another billion years further down the line, the oceans will be gone completely and Earth will really have become the third rock from the Sun.
As O’Malley-James said, “The far-future Earth will be very hostile to life by this point. All living things require liquid water, so any remaining life will be restricted to pockets of liquid water, perhaps at cooler, higher altitudes or in caves or underground".
In 2 billion years, life on Earth will still be clinging on but is likely to be confined to sporadic pockets of still remaining liquid water deep underground.
What will be driving these changes is the Sun. As the aeons pass, in a few billion years time, the Sun, while remaining stable, will gradually throw out more light and with light, heat. As a result, Earth will warm up, not just by a couple of degrees Celsius, but to such an extent that the increase in temperatures causes plant life and the oceans to disappear. O’Malley-James created a computer model to simulate these ultra-long range temperature predictions for Earth and used the results to predict the timescale for future extinctions. The research also has a bearing on understanding what may be the life-cycle of other worlds as more and more exoplanets — planets outwith our solar system — are discovered by the likes of NASA’s Kepler Space Telescope. The O’Malley-James model suggests that the search for extraterrestrial life may be a long and arduous one. The life-cycle hypothesis means that on other worlds, only the hardiest forms of microbial life may remain to be found, with other life-forms having long since ‘been and gone’.
Eventually, all species die off. Sometimes this can be caused by an extinction level event such as the giant impact from a meteor believed to have wiped out the dinosaurs on Earth. But even if Earth manages to dodge every near Earth orbit meteor and asteroid, the 10,000th of which was discovered by NASA barely more than a week ago, from now to eternity and beyond, the bottom line is that extinction will be slow and lingering even if the asteroids don’t get us. For when the day comes that our Sun ceases to be a life giver but switches to grim reaper mode, what is certain is that slow environmental changes will result in the extinction of all species on Earth. O’Malley-James predicts the last vestiges of life on Earth will have exited 2.8 billion years hence.
On the search for life elsewhere in the universe, O’Malley-James comments, "When we think about what to look for in the search for life beyond Earth our thoughts are largely constrained by life as we know it today, which leaves behind telltale fingerprints in our atmosphere like oxygen and ozone. Life in the Earth's far future will be very different to this, which means, to detect life like this on other planets we need to search for a whole new set of clues,"
and he added, "We have now simulated a dying biosphere composed of populations of the species that are most likely to survive to determine what types of gases they would release to the atmosphere. By the point at which all life disappears from the planet, we're left with a nitrogen:carbon-dioxide atmosphere with methane being the only sign of active life".
More about Astronomy, Exoplanets, Extinction, extinction level events, long term climate change
 
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