“We were stunned when the astronauts revealed in 1969 the beauty of our planet seen from space. It took Arthur C. Clarke, the science fiction writer and inventor, to observe how wrong it was to call this planet Earth when, clearly, it is Ocean,” says futurist James Lovelock, originator of the Gaia theory that views Earth as a living organism. “Despite being fifty years ago, this discovery that we live on an ocean planet is only just beginning to penetrate the dusty science of geology. It is shameful that we know far more about the surface of Mars and its atmosphere than we know about parts of our oceans. It is also risky.”
After the Sun, Earth’s oceans are the primary driver of our climate. It is vital for our survival that they are kept cool, below 15°C. Whenever the surface temperature of the ocean rises above 15°C, they become a desert more bereft of life than the Sahara.
As photographs from space show so dramatically, Earth is a water planet with nearly three-quarters of its surface covered by oceans. Life on land depends on the supply of certain essential elements such as sulphur, selenium, iodine and others. Just now these are supplied by ocean surface life as gases like dimethyl sulphide and methyl iodide. The loss of this surface life due to the heating of these waters would be catastrophic.
Climate-Change Event Horizon
On November 21, 2017, The Galaxy posted “The Climate-Change Event Horizon” –MIT Scientist Predicts the Tipping Point for Earth’s 6th Mass Extinction. MIT geophysicist Daniel Rothman predicts that given the recent rise in carbon dioxide emissions over a relatively short timescale, a sixth extinction will depend on whether a critical amount of carbon is added to the oceans. That amount, he calculates, is about 310 gigatons, which he estimates to be roughly equivalent to the amount of carbon that human activities will have added to the world’s oceans by the year 2100.
Does this mean that mass extinction will soon follow at the turn of the century? Rothman says it would take some time — about 10,000 years — for such ecological disasters to play out. However, he says that by 2100 the world may have tipped into “unknown territory.” “How can you really compare these great events in the geologic past, which occur over such vast timescales, to what’s going on today, which is centuries at the longest?” says MIT geophysicist Daniel Rothman. “So I sat down one summer day and tried to think about how one might go about this systematically.”
“This is not saying that disaster occurs the next day,” says Rothman about his new study. “It’s saying that, if left unchecked, the carbon cycle would move into a realm which would be no longer stable, and would behave in a way that would be difficult to predict. In the geologic past, this type of behavior is associated with mass extinction.”
Deciphering whether the recent spike in carbon could lead to mass extinction has been challenging. That’s mainly because it’s difficult to relate ancient carbon anomalies, occurring over thousands to millions of years, to today’s disruptions, which have taken place over just a little more than a century.
47°C sets the limit for any kind of life
“47°C sets the limit for any kind of life on an ocean planet like the Earth,” writes Lovelock in Novacene, his name for a new geological epoch of the planet, an age that succeeds the Anthropocene, which began in 1712 and is already coming to a close. “Once this temperature is passed, even silicon-based intelligence would face an impossible environment. It is even possible that the floor of the ocean would enter the supercritical state and in places where the magma emerged there would be no separation between rocks and supercritical-state steam.
“We should be amazed by and grateful for the remarkable achievement of the Gaia system in pumping down carbon dioxide to levels as low as 180 parts per million, the level it reached 18,000 years ago,” adds Lovelock. “It is now 400 parts per million and rising, with the burning of fossil fuel responsible for about half of this rise.”
Earth as Venus?
Without life, carbon dioxide would have been returned to the atmosphere as gas in geologically relatively recent times, and Earth would be just like Venus – a hot, dead planet.
It is very unlikely, Lovelock concludes, “that, in the imaginable future, the entire surface of the Earth will reach anything like 47°C. The current average temperature is about 15°C. But it is conceivable that, with feedback loops, especially the melting of the polar ice caps and methane released from permafrost, a global temperature of, say, 30°C may be a tipping point that could accelerate heating further.
Earth 55 Million Years Ago
“What is clear is that we should not simply assume, as most people do most of the time, that the Earth is a stable and permanent place with temperatures always in a range in which we can safely survive. Some 55 million years ago, for example, an event known as the Palaeocene/Eocene Thermal Maximum took place. This was a period of warming when temperatures rose about 5 degrees above their present level. Animals such as crocodiles lived in what are now the polar oceans, and all the Earth was a tropical place.”
The largest extinction in Earth’s history marked the end of the Permian period, some 252 million years ago. Long before dinosaurs, our planet was populated with plants and animals that were mostly obliterated after a series of massive volcanic eruptions in Siberia. Fossils in ancient seafloor rocks show a thriving and diverse marine ecosystem, then a swath of corpses. Some 96 percent of marine species were wiped out during the “Great Dying,” followed by millions of years when life had to multiply and diversify once more.
“Over the last 50 years, the oxygen in our oceans has decreased by around 2-5% and this is already having an effect on species’ ability to function,” said John Spicer, Professor of Marine Zoology at the University of Plymouth. “Unless they adapt, many larger marine invertebrates will either shrink in size or face extinction, which would have a profoundly negative impact on the ecosystems of which they are a part.”
The Daily Galaxy, Jon Payne, via Lovelock, James. Novacene (The MIT Press) . Kindle Edition.
Image credit: Whale shark with thanks to BBC Blue Planet 2