We're Doomed!
Posted on 02/17/2006 8:54:21 AM PST by cogitator
Human activities are releasing greenhouse gases more than 30 times faster than the rate of emissions that triggered a period of extreme global warming in the Earth's past, according to an expert on ancient climates.
"The emissions that caused this past episode of global warming probably lasted 10,000 years. By burning fossil fuels, we are likely to emit the same amount over the next three centuries," said James Zachos, professor of Earth sciences at the University of California, Santa Cruz.
Zachos will present his findings this week at the annual meeting of the American Association for the Advancement of Science (AAAS) in St. Louis. He is a leading expert on the episode of global warming known as the Paleocene-Eocene Thermal Maximum (PETM), when global temperatures shot up by 5 degrees Celsius (9 degrees Fahrenheit). This abrupt shift in the Earth's climate took place 55 million years ago at the end of the Paleocene epoch as the result of a massive release of carbon into the atmosphere in the form of two greenhouse gases: methane and carbon dioxide.
Previous estimates put the amount of released carbon at 2 trillion tons, but Zachos showed that more than twice that amount--about 4.5 trillion tons--entered the atmosphere over a period of 10,000 years (Science, June 10, 2005). If present trends continue, this is the same amount of carbon that industries and automobiles will emit during the next 300 years, Zachos said.
Once the carbon is released into the atmosphere, it takes a long time for natural mechanisms, such as ocean absorption and rock weathering, to remove excess carbon from the air and store it in the soil and marine sediments. Weathering of land rocks removes carbon dioxide permanently from the air, but is a slow process requiring tens of thousands of years. The ocean absorbs carbon dioxide much more rapidly, but only to a point. The gas first dissolves in the thin surface layer of the ocean, but this surface layer quickly becomes saturated and its ability to absorb more carbon dioxide declines.
Only mixing with the deeper layers can help restore the ability of the surface water to absorb additional carbon dioxide from the atmosphere. But the natural processes that mix and circulate water between the ocean surface and deeper ocean layers work very slowly. A complete "mixing cycle" takes about 500 to 1,000 years, Zachos said.
The greenhouse emissions that triggered the PETM initially exceeded the ocean's absorption capacity, allowing carbon to accumulate in the atmosphere. Unfortunately, humans appear to be adding carbon dioxide to the air at a much faster rate: about the same amount of carbon (4.5 trillion tons), but within a few centuries instead of 10,000 years. What was emitted 55 million years ago over a period of about 20 ocean mixing cycles is now being emitted over a fraction of a cycle.
"The rate at which the ocean is absorbing carbon will soon decrease," Zachos said.
Compounding this concern is the possibility that higher temperatures could retard ocean mixing, further reducing the ocean's capacity to absorb carbon dioxide. This could have the kind of "positive feedback" effect that climate researchers worry about: reduced absorption, leaving more carbon dioxide in the air, causing more warming.
Higher ocean temperatures could also slowly release massive quantities of methane that now lie frozen in marine deposits. A greenhouse gas 20 times more potent than carbon dioxide, methane in the atmosphere would accelerate global warming even further.
Such positive feedback or "threshold" effects probably drove global warming during the PETM and a few other ancient climate extremes, Zachos said, and they could happen again. It is possible that we already are in the early stages of a similar climate shift, he said.
"Records of past climate change show that change starts slowly and then accelerates," he said. "The system crosses some kind of threshold."
Clues to what happened during the PETM lie buried deep inside the sediment at the bottom of the sea, which Zachos and his colleagues have probed during several cruises of the Ocean Drilling Program (ODP). Composed mainly of clay and the carbonate shells of microplankton, this sediment accumulates slowly, but steadily--up to 2 centimeters every millennium--and faithfully records changes in ocean chemistry. The layer of sediment deposited during the PETM, now buried hundreds of meters below the seafloor, tells a clear and compelling story of sudden change and slow recovery, he said.
During the PETM, unknown factors released vast quantities of methane that had been lying frozen in sediment deposits on the ocean floor. After release, most of the methane reacted with dissolved oxygen to form carbon dioxide, which made the seawater more acidic. Acidic seawater corrodes the carbonate shells of microplankton, dissolving them before they can reach the ocean floor and reducing the carbonate content of marine sediment.
Zachos led an international team of scientists that analyzed sediment cores recovered from several locations during an ODP cruise in the southeastern Atlantic. Collected at depths ranging from 2.5 to 4.8 kilometers (1.6 to 3.0 miles), each sediment core bore a telltale PETM imprint: a 10- to 30-centimeter layer of dark red carbonate-free clay sandwiched between bright white carbonate-rich layers.
by relating the thickness of the clay layer to the rate of accumulation of marine sediment, Zachos estimated that it took 100,000 years after the PETM for carbon dioxide levels in the air and water to return to normal. This finding is consistent with what geochemists have predicted using models of how the global carbon cycle will respond to carbon dioxide emissions from the burning of fossil fuels.
"We set out to test the hypotheses put forward by a small group of geochemists who model the global carbon cycle, and our findings support their predictions," Zachos said. "It will take tens of thousands of years before atmospheric carbon dioxide comes down to preindustrial levels. Even after humans stop burning fossil fuels, the effects will be long lasting."
And what exactly do animals do in this system?
No one considers that as the CO2 level increases and as temperature increases then so too does the photosynthetic efficiency of plants.
So scientists have determined that past climate change is entirely a function of emissions. Sounds like a emission to me....
In the case of the PETM, the release was, with near certainty, the cause of the warming. The PETM is a very interesting climate "incident" -- I've never been able to find a discussion of what triggered the release. But the temperature increase clearly lags the increasing carbon dioxide and methane concentrations in the atmosphere.
I can find links for you, or you can Google for them yourself. Goddard Institute of Space Studies had an article about "ocean burps" that I've posted here a few times.
Is it time to start running around in circles and screaming "we are doomed, we are doomed"?
I just read it and I agree; it's awesome.
The greeny's PR houses are cranking out this crap all this week in tune with the first anniversary of the so-called implementation of the so-called Kyoto Accords that nobody is honoring.
Geee whizzzz....I didn't know that we had "climatologists" 30,ooo years ago. You learn something new every day!
If the Democrats ever get back into control, I'm sure they'll fix it though. (/sarc.)
Well, if the scientists say it, then I have to accept it. Although I'll no doubt be ridiculed, I do not have the independent training to argue the findings or the math or the models. (In other words, I have the wrong graduate degree to talk to scientists.)
Everyone says global warming is a fact, especially scientists. People who are skeptical about it are derided as ignorant. So I'm sticking with the scientists on this one. Global warming is a fact, people. We need to do everything the scientists tell us to do in order to save our planet. We need to cut out on emissions that cause greenhouse gases... or whatever.
Weren't no dinosaurs around 55 MYA.
In yet other news, studies of political campaigns suggest Democratic Party and liberalism on fast track to nowhere.
Read Tom Clancy's 'Rainbow Six'.
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