BP - before present .
Posted on 02/02/2004 12:16:15 PM PST by presidio9
UK scientists claim they now know how Earth recovered on its own from a sudden episode of severe global warming at the time of the dinosaurs. Understanding what happened could help experts plan for the future impact of man-made global warming, experts say.
Rock erosion may have leached chemicals into the sea, where they combined with carbon dioxide, causing levels of the greenhouse gas to fall worldwide.
UK scientists report the details of their research in the journal Geology.
About 180 million years ago, temperatures on Earth rapidly shot up by about 5 Celsius.
The cause is thought to have been a sudden release of huge amounts of methane from the sea bed. Methane is itself a greenhouse gas but it is short-lived.
However, it is easily oxidised to carbon dioxide (CO2) which lingers in the atmosphere for long periods of time.
Mass extinction
Plants and animals were affected by the sudden rise in atmospheric CO2. Scientists have found evidence of a marine mass extinction during this period that killed off 84% of bivalve shellfish.
Over a period of about 150,000 years, the Earth returned to normal and life continued flourishing. How this happened was a mystery, but now scientists from the Open University in Milton Keynes claim to have a possible answer.
"Our new evidence has shown that this warming caused the weathering of rocks on the Earth's surface to rapidly increase by at least 400%," said Dr Anthony Cohen, who led the research.
"This intense rock-weathering effectively put a brake on global warming through chemical reactions that consumed the atmosphere's extra carbon dioxide."
They discovered that the rock had been subjected to high rates of weathering facilitated by warm conditions during the Jurassic hot spell.
'Methane burp'
Weathering occurs through the action of rain. Although the researchers did not uncover direct evidence for increased precipitation, they believe there were no limitations on water during the period.
The warm conditions caused by the "methane burp" would have sped up the rate at which weathering occurred. This led to minerals such as calcium and magnesium eroding from rocks and pouring into the sea.
Calcium combined with CO2, for instance, would have caused the precipitation of calcium carbonate. This process of CO2 consumption would have lowered levels of the greenhouse gas on a global scale.
As CO2 levels fell, so did global temperatures.
"Global warming is affecting the climate today, but it's very difficult to predict what's going to happen," Dr Cohen told BBC News Online.
"The reason for doing these studies is that you get the whole history. If you learn what happened then, that can inform how you deal with [the same problem] in future."
Dr Cohen added that there are still vast reserves of carbon - possibly as much as 14,000 gigatons - locked up as methane ice in ocean sediments.
If global temperatures reach a critical point, it is possible they might suddenly be released into the atmosphere causing a similar event to the one that occurred during the Jurassic.
"What we have learned from these rocks is how the Earth can, over a long time, combat global warming. What we need to discover now is why and at what point it goes into combat mode, and precisely how long the conflict takes to resolve," he explained.
Dr Cohen and his colleagues based their results on studies of mudrock rich in organic material and collected near Whitby in North Yorkshire.
BP - before present .
Who'd have thought that Taco Bell had submersible franchises that long ago?
LOL you'd never tell it from the article.
Science - Never hedge a good story with the facts.
Not trying to make fun of methane burps, which I take very seriously (especially in small cars when the windows won't go down), but today I'm more concerned about the fact that global warming is actually making things colder where I live right now.
Some CO2 history from the Vostok ice cores ---appears to cycle
Some temperature trends from the Vostok ice cores --- also appears to cycle.
LOL, only problem is temperature increases occur before the increases in CO2.
Increased temperatures from deep iceages leads to growth of biomass & warming of oceans releasing higher concentrations of CO2 into the atmosphere.
- "(1) correlation does not prove causation, (2) cause must precede effect, and (3) when attempting to evaluate claims of causal relationships between different parameters, it is important to have as much data as possible in order to weed out spurious correlations.
***
Consider, for example, the study of Fischer et al. (1999), who examined trends of atmospheric CO2 and air temperature derived from Antarctic ice core data that extended back in time a quarter of a million years. Over this extended period, the three most dramatic warming events experienced on earth were those associated with the terminations of the last three ice ages; and for each of these climatic transitions, earth's air temperature rose well in advance of any increase in atmospheric CO2. In fact, the air's CO2 content did not begin to rise until 400 to 1,000 years after the planet began to warm. Such findings have been corroborated by Mudelsee (2001), who examined the leads/lags of atmospheric CO2 concentration and air temperature over an even longer time period, finding that variations in atmospheric CO2 concentration lagged behind variations in air temperature by 1,300 to 5,000 years over the past 420,000 years."[ see also: Indermuhle et al. (2000), Monnin et al. (2001), Yokoyama et al. (2000), Clark and Mix (2000) ]
- "Other studies periodically demonstrate a complete uncoupling of CO2 and temperature "
[see: Petit et al. (1999), Staufer et al. (1998), Cheddadi et al., (1998), Raymo et al., 1998, Pagani et al. (1999), Pearson and Palmer (1999), Pearson and Palmer, (2000) ]
- "Considered in their entirety, these several results present a truly chaotic picture with respect to any possible effect that variations in atmospheric CO2 concentration may have on global temperature. Clearly, atmospheric CO2 is not the all-important driver of global climate change the climate alarmists make it out to be."
Global warming and global dioxide emission and concentration:
a Granger causality analysis
- "We find, in opposition to previous studies, that there is no evidence of Granger causality from global carbon dioxide emission to global surface temperature. Further, we could not find robust empirical evidence for the causal nexus from global carbon dioxide concentration to global surface temperature."
I would submit that global warming is relative and the current cold temperatures over the last 2 million years or so is not Earth-normal.
It's just the cycle (cirle?) of life. Things come, things go. There is no good, no bad, just what is.
Perhaps the planet needs to divest itself of most life and restart every few millennia to keep itself in balance.
Or do you think humanity is somehow so important as to be worthy of changing the cycle?
Shalom.
Researchers at Woods Hole Institute have been theorizing that global warming could have a deleterious effect on the Gulf Stream for years.
The collapse of the ice dams holding Lake Agazzis was the 'trip-wire' for the Younger-Dryas 8BC event, that is used to infer the possibility of such a catastrophe today.
Fortunately there are no analogs of Lake Agazzis and it's ice dams left to perform the same task today. They have all melted from the 10oC warming across the last 10,000yrs that brought to our current climate conditions.
It began as an obscure theory from the fringes of scientific thinking on climate, the idea that `global warming' could conspire to plunge Europe and the northeast of North America into a new ice age - and do so within our lifetimes.
The theory basically says that an increasing influx of fresh water into the North Atlantic `could' disrupt the natural sinking of salt water in the Arctic seas off Norway which draws warmer water from the south - the Gulf Stream which warms Europe. With no Gulf Stream, Europe `could' plunge into similar climatic conditions as those of Labrador, Canada, which is on similar latitudes. In other words, global warming could trigger a new ice age in Europe.
And the precedent for this outlandish scenario? 10,700 years ago, such an event did occur - the `Younger Dryas', where humungous floods of fresh water running off the melting ice caps over North America and Europe did freshen the North Atlantic sufficiently to shut down the Gulf Stream for about 300 years. Once these ice caps had melted away, the North Atlantic became sufficiently salty again to allow the Gulf Stream to re-establish itself.
But where will these enormous quantities of fresh water come from today? The industry says, coyly, `more rainfall' - from global warming. This is an absurd proposition because no amount of rain could rival the massive melt-water runoff that occurred during the Younger Dryas. If the Gulf Stream were weakening, there would be an expansion of Arctic sea ice into the high North Atlantic where the Gulf Stream finally sinks to the ocean depths, returning via the ocean floor. But no such ice expansion is taking place. Indeed, some scientists claim that sea ice is shrinking, not expanding, which suggests the Gulf Stream is as strong, or stronger, than ever.
It's certainly worth studying.
It has been repeatedly, google "Younger Dryass", or "Lake Agazzis" you will find endless such studies.
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