[Iain]

This story in the Guardian raises the disturbing possibility that the Earth may be having more problems than previously thought absorbing the additional CO2 we are pumping into the atmosphere. Early days yet - I believe this finding still has to be confirmed (or otherwise) by other research centres.

There are many precedents for runaway accelerated global change in Earth's history - all are very bad for the species around at the time.

Measurements of CO2 in the atmosphere have been continuous for almost 50 years at Mauna Loa Observatory, 12,000ft up a mountain in Hawaii, regarded as far enough away from any carbon dioxide source to be a reliable measuring point.

In recent decades CO2 increased on average by 1.5 parts per million (ppm) a year because of the amount of oil, coal and gas burnt, but has now jumped to more than 2 ppm in 2002 and 2003.

Above or below average rises in CO2 levels in the atmosphere have been explained in the past by natural events.

When the Pacific warms up during El Niño - a disruptive weather pattern caused by weakening trade winds - the amount of carbon dioxide rises dramatically because warm oceans emit CO2 rather than absorb it.

But scientists are puzzled because over the past two years, when the increases have been 2.08 ppm and 2.54 ppm respectively, there has been no El Niño.

"It is possible that this is merely a reflection of natural events like previous peaks in the rate, but it is also possible that it is the beginning of a natural process unprecedented in the record."

Analysts stress that it is too early to draw any long-term conclusions.

But the fear held by some scientists is that the greater than normal rises in C02 emissions mean that instead of decades to bring global warming under control we may have only a few years. At worst, the figures could be the first sign of the breakdown in the Earth's natural systems for absorbing the gas.

That would herald the so-called "runaway greenhouse effect", where the planet's soaring temperature becomes impossible to contain. As the icecaps melt, less sunlight is refected back into space from ice and snow, and bare rocks begin to absorb more heat. This is already happening.

This is from a newspaper; I'll be interested to see what New Scientist or Scientific American have to say about it. Also, as the article makes clear, it could still be unknown natural causes and it is early days. One to watch, though.

[Unperson-S]

Heres some more on 'Runaway green-house effect' :

A Runaway Greenhouse
Effect?

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The Earth and Venus are near each other in the Solar System, and are similar in size, density, and composition. Based on our understanding of the origin of the Solar System, we would expect that their initial atmospheres would have been rather similar. Yet the present atmospheres of the two planets could hardly be much more different than they are. How did this come to be? The reason is thought to lie in what is termed the "Runaway Greenhouse Effect".

Radiation Trapping by Greenhouse Gases
Sunlight falling on the surface of a planet is primarily in the visible part of the spectrum. However, the reflection of light from the surface tends to produce light of longer wavelength called infrared (IR) radiation (also known as radiant heat; IR radiation is the heat that we sense being radiated from a hot surface like a hot piece of metal).
Now, because of their molecular structures, certain gases like carbon dioxide and water vapor (and many others) have the property that they are essentially transparent to visible light but absorb IR radiation very strongly. Such compounds are sometimes termed greenhouse gases because, if they are present in a planetary atmosphere, they absorb the scattered IR radiation and tend to raise the temperature of the atmosphere by trapping solar energy. (The analogy with a real greenhouse is imperfect because the mechanism by which a greenhouse stays warm is different, but it is sufficiently good that the name "(Planetary) Greenhouse Effect" is now the common one for this phenomenon.)

The Greenhouse Effect Out of Control
The greenhouse effect occurs for all planetary atmospheres containing greenhouse gases, and is responsible for their being warmer than would be the case otherwise. The greenhouse effect by itself could not account for the conditions that we find on Venus. However, under certain conditions we believe the greenhouse effect can "run away". For example, consider the case of a planet like the Earth. The Earth has enormous amounts of two greenhouse gases: water vapor and carbon dioxide. However, for the Earth most of the water and carbon dioxide are not in the atmosphere. The water is mostly in the oceans, and the carbon dioxide is mostly bound chemically in rocks made from compounds that chemists call carbonates (for example, limestone).
Now suppose we increased the effectiveness of greenhouse heating of the Earth's atmosphere, for example by increasing the amount of solar radiation falling on it, or by increasing the concentration of greenhouse gases in the atmosphere (for example, by burning fossil fuels, which produce water vapor and carbon dioxide as byproducts of burning). We would then expect the temperature to rise in the atmosphere (assuming no other effects intervened---a big "if" in the realistic case since the atmosphere is complicated). This would be a greenhouse effect.

. . . and the Oceans Would Boil
It would become a runaway greenhouse effect if the rising temperature approached the boiling point of water, because then the oceans would begin to convert to water vapor, the water vapor would increase the effectiveness of heat trapping and accelerate the greenhouse effect, this would cause the temperature to rise further, thus causing the oceans to evaporate faster, etc., etc. (This type of runaway is also called a "positive feedback loop".) When the oceans were gone the atmosphere would finally stabilize at a much higher temperature and at much higher density, because all the water would now be in the atmosphere.
. . . and the Rocks Would Sublimate
We can envision even a further runaway stage in this scenario. Suppose the preceding runaway raised the temperature so high that chemical reactions begin to occur that drive the carbon dioxide from the rocks into the atmosphere (the process is called sublimation; a few hundred degrees Celsius would be sufficient). Then another runaway would occur as the carbon dioxide feeding into the atmosphere would accelerate the heating, which would in turn accelerate the transfer of carbon dioxide from the rocks to the atmosphere.
The Mother of All Environmental Disasters
The atmosphere would finally stablilize at a still higher temperature and pressure after all the carbon dioxide had been driven from the rocks. In fact, we believe that if this sequence were to take place on the Earth, the resulting temperature and pressure of the atmosphere left behind would not be very different from that for present-day Venus: the atmospheric termperature would be hundreds of degrees Celsius and the pressure would be maybe 100 times greater than it is today.
Thus, we believe that in the case of Venus the initial solar heating kept oceans from forming, or kept them from staying around if they did form, and the subsequent lack of rainfall and failure of plant life to evolve kept the carbon dioxide in the atmosphere rather than binding it in the rocks as is the case for the Earth; thus, Venus has an environmental disaster for an atmosphere.

The sobering warning for us is obvious: we have to be extremely concerned about processes such as burning of fossil fuels in large volumes that might (we don't know for sure because the scientific questions are complex) have the potential to trigger a runaway greenhouse effect and produce on the Earth atmospheric conditions such as those found on Venus.

But the most important things :

. . . and the Oceans Would Boil
It would become a runaway greenhouse effect if the rising temperature approached the boiling point of water, because then the oceans would begin to convert to water vapor, the water vapor would increase the effectiveness of heat trapping and accelerate the greenhouse effect, this would cause the temperature to rise further, thus causing the oceans to evaporate faster, etc., etc. (This type of runaway is also called a "positive feedback loop".) When the oceans were gone the atmosphere would finally stabilize at a much higher temperature and at much higher density, because all the water would now be in the atmosphere.
. . . and the Rocks Would Sublimate
We can envision even a further runaway stage in this scenario. Suppose the preceding runaway raised the temperature so high that chemical reactions begin to occur that drive the carbon dioxide from the rocks into the atmosphere (the process is called sublimation; a few hundred degrees Celsius would be sufficient). Then another runaway would occur as the carbon dioxide feeding into the atmosphere would accelerate the heating, which would in turn accelerate the transfer of carbon dioxide from the rocks to the atmosphere.

The Mother of All Environmental Disasters
The atmosphere would finally stablilize at a still higher temperature and pressure after all the carbon dioxide had been driven from the rocks. In fact, we believe that if this sequence were to take place on the Earth, the resulting temperature and pressure of the atmosphere left behind would not be very different from that for present-day Venus: the atmospheric termperature would be hundreds of degrees Celsius and the pressure would be maybe 100 times greater than it is today.

http://csep10.phys.utk.edu/astr161/lect ... house.html

If this is correct, then, in actually, within a few hundred years - at most, at our current rate, we could have similar weather conditions as Venus, in other words, the human race will be wiped out.

But, this is not taking into account, that we will no longer have fossil fuels, or as much as we use them, in around maximum of 50 years, but human activity, and further war - e.g. testing of nuclear weapons, will increase the temperature - short term, but could trigger a global heat wave, one of unimaginable scale, if linked in with high pollutant levels.

[Iain]

A runaway greenhouse effect is a possibility; but I don't know how likely it is.

The Earth has had runaway climates before (hot and cold); but they've never got so bad that all life has been extinguished and the Earth has managed to recover after a few tens of millions of years (not that either of those are much consolation to the human race).

Three big differences between Venus and Earth : we have a molten inside to the planet, we have a very large moon (really a companion planet - it's bigger than Pluto) and although we are near Venus, we are a bit further out and that bit might make all the difference.

[Unperson-S]

I agree, but, the fact is that Venus never had any unnatural forces playing with it. I never said that it will happen, just a possibility. I realise, that the Earth will never turn into a planet like Venus, because Venus is made up very differently, and has thoushands more volcanoe's than Earth, which is something that man will never be able to create, but, we have our own problems, which could attribute to our climate becoming somewhat of a Venus scenario.

[Demosthenes]

Analysts stress that it is too early to draw any long-term conclusions.

This is the most important sentance in the whole document. Global Warming (as caused by human hand) is not proven by any stretch of the imagination.

[Iain]

This is the most important sentance in the whole document. Global Warming (as caused by human hand) is not proven by any stretch of the imagination.

Unfortunately for your argument the sentence doesn't refer to human-caused global warming, but to the particular question of whether the earth has hit a limit in the amount of CO2 it can absorb.

Nice try, though

[Demosthenes]

Oh, there's more trust me...and I intentionally took it out of context to make the point.

I am researching this topic right now for a paper I'll be finishing on Friday. I'll be sure to share my results here.

But I know, you folks really need for this to be happening, and for it to be all man's fault so I won't hold my breath.

[Iain]

Oh, there's more trust me...and I intentionally took it out of context to make the point.

A point about the way you approach evidence?

I am researching this topic right now for a paper I'll be finishing on Friday. I'll be sure to share my results here.

Please do.

But I know, you folks really need for this to be happening, and for it to be all man's fault so I won't hold my breath.

From a sceptical position, I've been persuaded over the last few years by the evidence I've seen, first that global warming is happening and secondly that in the last 50 years human activity has significantly affected it. I've never claimed it was all man's fault and never for a moment thought that global warming was not in part due to natural processes.

To suggest that those who see evidence for global warming as being some sort of faith issue is a cheap shot and, I would have thought, beneath serious discussion on the topic.

I trust your paper will stick to the evidence and not resort to ad-hom attacks and quoting out of context to make your case.

[Demosthenes]

Ok, I don't want to bicker with you. The thing I like about science (except this particular topic) is that, for the most part, you stick to immutable facts. (gravity, thermonuclear reactions, etc.) As such people can have all manner of personal political positions but still find some common ground amongst scientific principles. Of course, I'm no scientist but as an amatuer I still identify with that.

So...I was JOKING about the environmental whacko thing, in the beginning. Ocker got it...that's why he joked back with me.

The other comment that your so offended because of it's use out of context, was also tongue in cheek. To imply that I now have a mark against me for it, it simply overalyzing the comment.

At any rate, I can already tell you won't like the paper, but I'll post it anyway, and will leave sourses intact so you can scrutinize them to your hearts content.

I just wish this science was as easily debatable as most others and didn't generate such over emotional reactions and partisanship. But I guess you can wish for anything.

[Iain]

Apologies if I didn't get the joke. I'm sure I won't agree with your paper, but I should have the time to read it and hopefully offer some "constructive criticism"

I think all science can raise high emotions in debates. Look at the emotions in the Dawkins vs Gould debates, or even in the debates over the classification systems for flora and fauna. It's natural and probably a good thing as long as the science isn't overshadowed. After all, science is exciting and potentially world-changing so it would be a bit strange if people didn't get worked up about things.