From the latest issue of Science comes a study by paleoecologists at the University of Copenhagen’s Nordic Center for Earth Evolution, that the Triassic extinction event was caused by global climate change, first brought about by CO2 emissions from volcanic activity that then warmed the oceans sufficiently to release previously frozen deposits of methane from the ocean floor. From the Abstract:
The end-Triassic mass extinction (~201.4 million years ago), marked by terrestrial ecosystem turnover and up to ~50% loss in marine biodiversity, has been attributed to intensified volcanic activity during the break-up of Pangaea. Here, we present compound-specific carbon-isotope data of long-chain n-alkanes derived from waxes of land plants, showing a ~8.5 per mil negative excursion, coincident with the extinction interval. These data indicate strong carbon-13 depletion of the end-Triassic atmosphere, within only 10,000 to 20,000 years. The magnitude and rate of this carbon-cycle disruption can be explained by the injection of at least ~12 × 103 gigatons of isotopically depleted carbon as methane into the atmosphere. Concurrent vegetation changes reflect strong warming and an enhanced hydrological cycle. Hence, end-Triassic events are robustly linked to methane-derived massive carbon release and associated climate change.
Micha Ruhl and colleagues from the University of Copenhagen’s Nordic Center for Earth Evolution have published a paper in Science where they contend that the mass extinction that occurred at the end of the Triassic period, was due to a “sudden” increase in the amount of methane in the atmosphere due to the effects of global warning that resulted from the spewing of carbon dioxide from volcanoes.
… Ruhl et al contend that … what happened, was that the small amount of atmospheric heating that occurred due to the exhaust from the volcanoes, caused the oceans to warm as well, leading to the melting of ice crystals at the bottom of the sea that were holding on to methane created by the millions of years of decomposing sea life. When the ice crystals melted, methane was released, which in turn caused the planet to warm even more, which led to more methane release in a chain reaction, that Ruhl says, was the real reason for the mass extinction that led to the next phase in world history, the rise of dinosaurs.
Methane is a far more powerful greengouse gas, roughly 20 times more powerful than CO2. Thus, it accelerates warming much quicker than CO2 bu=y itself.
So, how much methane was released at the end of the Triassic period? A helluva lot (from the NY Times):
Two hundred million years ago, at the end of the Triassic period, a mass extinction, often attributed to major volcanic activity, wiped out half of all marine life on Earth. But new research published in the journal Science suggests that the extinction was more likely to have been caused by the release of at least 12,000 gigatons of methane from the seafloor into the atmosphere.
Numerically 12,000 gigatons = 12,000 BILLION Tons = 12,000,000,000,000 tons of methane. In other words, TWELVE TRILLION TONS.
Guess what greenhouse gas is being released at an alarming rate as our oceans are warmed by the constant increase in CO2 emissions created by human activity? That;s right! Methane! In Siberia!
Arctic seabed stores of methane are now destabilizing and venting vast stores of frozen methane—a greenhouse gas 30 times more potent than carbon dioxide. The paper, in the prestigious journal Science, reports the permafrost under the East Siberian Arctic Shelf—long thought to be an impermeable barrier sealing in methane—is instead perforated and leaking large amounts of methane into the atmosphere. Melting of even a fraction of the clathrates stored in that shelf could trigger abrupt climate warming. Lead author Natalia Shakhova Shakhova of the International Arctic Research Center tells U of Alaska Fairbanks:
“The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the entire world’s oceans. Subsea permafrost is losing its ability to be an impermeable cap.”
The East Siberian Arctic Shelf is a methane-rich area encompassing more than three-quarter million square miles of seafloor in the Arctic Ocean—three times larger than the nearby Siberian wetlands formerly considered the primary Northern Hemisphere source of atmospheric methane.
Shakhova’s research shows the East Siberian Arctic Shelf is already emitting 7 teragrams (1 teragram = 1.1 million tons) of methane yearly, about as much as the all the oceans of the world.
And not just Siberia, but from freshwater lakes and rivers too:
An international team of scientists, which includes John Downing, an Iowa State University professor in the ecology, evolution and organismal biology department, has found greenhouse gas uptake by land environments such as forests is less than previously thought because of methane emissions from freshwater areas. Methane is considered a greenhouse gas.
The study, published in the journal Science, finds methane gas release from freshwater areas changes the net absorption of greenhouse gases by natural land environments by at least 25 percent. Before, estimates of carbon and greenhouse gas exchanges on continents did not account for the methane gas that is produced by lakes and running water.
Downing compared the discovery to finding a large error in a financial budget.
“This is really a pretty big error,” he said. “Imagine being off 25 percent in your accounting. It could sink your budget.”
In the same way, Downing said, the study reveals that an underestimation in the amount of methane gas released by freshwater bodies may have made previous estimates about the rate of climate change inaccurate.
And, of course, from the oceans, such as the rapidly warming Arctic Ocean:
Scientists have uncovered what appears to be a further dramatic increase in the leakage of methane gas that is seeping from the Arctic seabed. […]
The findings come from measurements of carbon fluxes around the north of Russia, led by Igor Semiletov from the University of Alaska at Fairbanks.
“Methane release from the East Siberian Shelf is underway and it looks stronger than it was supposed [to be],” he said.
So how much methane is trapped under our ever warming oceans today? Well no one knows for certain. Here’s what the USGS has to say on the matter in 1992:
Gas hydrates occur abundantly in nature, both in Arctic regions and in marine sediments. Gas hydrate is a crystalline solid consisting of gas molecules, usually methane, each surrounded by a cage of water molecules. It looks very much like water ice. Methane hydrate is stable in ocean floor sediments at water depths greater than 300 meters, and where it occurs, it is known to cement loose sediments in a surface layer several hundred meters thick.
The worldwide amounts of carbon bound in [methane] gas hydrates is conservatively estimated to total twice the amount of carbon to be found in all known fossil fuels on Earth.
Recent estimates of methane gas hydrates (clathrates) under the ocean are quite immense
Vast quantities of methane are trapped in oceanic hydrate deposits, with estimates of 3,000, 10,000, or even 74,000 gigatons of methane carbon trapped as hydrate in ocean sediments. An increase in temperatures at the seafloor, driven by climate change, could dissociate some of these hydrates, leading to methane release into the ocean and perhaps eventually into the atmosphere. Because methane is a powerful greenhouse gas, there is concern that such a release could have adverse consequences.
So the estimates of methane trapped under our oceans is anywhere from Three Trillion Tons to 74 Trillion Tons. Remember, a release of 12 Trillion Tons may have led to one of the five largest extinction events in earth’s history. So it would appear that we have sufficient methane hydrates available to accelerate global warming and climate change to levels not seen since the end of the Triassic Period, should the release of that methane continue to accelerate. We know the methane is already leaking from the Arctic ocean and from the permafrost of Siberia where some of the most rapid warming on the planet is occurring.
We also know that oil and gas companies are actively seeking how to exploit deep sea floor methane hydrates. Interest strong enough to propose international treaties to permit exploiting this “resource” in the Arctic and elsewhere:
Political and economic interest groups would argue that it is a waste not to use methane hydrates when the exploitation of this resource will aid development. They may use simplistic, populist demagogy to encourage public acceptance of methane hydrate extraction without complete understanding of the long-term consequences.
For these reasons, it is necessary to establish a mechanism to (1) promote research on the possible effects of extracting methane hydrates from the ocean floor; (2) provide clear property rights for methane hydrate deposits located in international waters; and (3) regulate the inducement of methane hydrate use in future power systems design.
This is not good news for the potential survival of millions of species on earth, including perhaps the current dominant species, homo sapiens sapiens. It tells us that CO2 releases can warm the planet enough to trigger massive methane releases that then make a drastically warmer world an irreversible reality for thousands if not hundreds of thousands of years.
The study could be foreshadowing the effect of climate change on Earth, Dr. Ruhl said. An increase of carbon dioxide in the atmosphere from fossil-fuel use could warm up the planet enough to release methane from the ocean floors, he said.
“Methane is a much stronger greenhouse gas than CO2, so potentially that could result in a strong increase in temperature and climate change,” he said.
