Firm Evidence for Greenhouse Effect

(outer-limits) pointed us to this AP story which describes a study published in Nature: a comparison of infrared data from 1970 and 1997 shows that the Earth is definitely re-radiating less energy in the bands absorbed by greenhouse gases. What does this mean for global warming? <shrug> Nobody knows.

Comments

Skin cancer myth

[XNormal]

The skin cancer story is often used by well-meaning environmentalists to scare people. In fact, the increase in ultraviolet radiation from moving a hundred miles closer to the equator is much greater than the maximum increase anticipated by the worst-case ozone depletion scenarios. Differences in lifestyle also have orders of magitude greater effect on the total UV dose you receive.

I don't like it when people spread inaccurate information. Not even for a good cause. For example, the fighting drug abuse would be served better by reliable information about drugs than by irresponsible lines and inaccurate scare stories.

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Sunspots

[NTSwerver]

There is another school of thought that believes earth's temperature, and even weather (clouds, to be exact), is affected by Sunspots.

Sunspots increase the Sun's magnetic field which acts as a kind of barrier helping to protect the Earth from cosmic rays. This acts as insulation and increases the Earth's overall temperature. When there are fewer Sunspots on the Sun's surface, it's magnetic field reduces allowing more cosmic rays to reach the Earth which cools the Earth. For example, in the late 17th century, there was hardly any Sunspot activity on the Sun's surface. This period coincided with the "Little Ice Age" when rivers on the Earth remained frozen all year round.

This research is on-going. At CERN, for example, tests are being undertaken with the particle accelerator to see if cosmic rays can affect cloud formation.

What this all means is that our predictions about global warming due to the Greenhouse Effect may have been greatly exaggerated.

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Re:Sunspots

[nerdygeek]

You said that, "Sunspots increase the Sun's magnetic field." Sunspots are one of many features associated with solar activity - they are a symptom of the changing solar magnetic field, rather than the cause of it. It's a bit like saying that sunburn causes a sunny day, rather than the other way round.

There is a lot of evidence that the solar cycle has an effect on the atmosphere and climate. Saying things like cosmic rays "cool the Earth" or that a lack of them "acts as insulation" is stating the fanciful and the unproved. The link between solar activity and climate is not a new idea, and there is a lot of work already done on more concrete mechanisms. For example, the solar UV radiation (which varies considerably with the solar cycle) effects levels of ozone in the stratosphere.

People in the field are well aware of the effect of the solar cycle and suggesting that their ignorance of this fact has lead to, "predictions about global warming due to the Greenhouse Effect [possibly being] greatly exaggerated" is wrong. The effect may have been overestimated, but not because the academics forgot about solar activity.

It should be remembered that this paper is about increases in green-house gasses. It doesn't attempt to say they have seen an increase in the Earth's temperatrure.

Re:Too much theories??

[NoNeeeed]

The theory is a bit more complex, but you have it about right.

When the ice caps melt, the cold fresh water will form a layer over the warmer but more salty water of the gulf stream. This effectively prevents the warm water from rising (water doesn't mix as fast as you would think). The result of this is that something called the globl conveyor, a series of warm ocean current that flow round the earth and distribute heat from the tropics to the poles will stop. These current basically keep areas like northern europe warmer than they would otherwise be. if my memory serves me right, London is at the same latitude as Moscow, the only reason we are so much warmer is because of the gulf stream bringing warmer (and wetter :-
In theory, if the global conveyor does stop, then the isea will get colder. The effect of this is that the tropics will get warmer (due to the general increase in temperature) while the more northerly areas get colder. The most worrying aspect of this is that the effective growing reagions of the world will be squeezed from both sides. The deserts will grow from the equator (that includes the US grain belt), making many areas too hot to farm effectively, while the nothern and sothern temperate zones will get much colder and dryer becuase of reduced transpiration (now there is a word I havn't used in a long time, means the cumulative effect of evaporation from the seas and plants). Basically the worlds prime growing land is going to be squeezed between an ice burg and a desert.

What no one knows is how the global climate will react to this. It is increadibly complex and feedback mechanisms that we don't know about may kick in and either accelerate the effect, or limit it. No one really knows. We could end up with a complete reversal over the next few hundred/thousand years. The ice caps grow, reflecting more light, which means a drop in temerature, which leads to more ice growth and so on. The snowball earth theory.

Over geograpical time the earth is capable of taking care of itself. We could nuke the entire place and things would regrow over the next few (hundred) million years. Unfortunatly humans do not live on the geographical time scale, so we have to care about what happens in the short (or relatively short for the earth) time.

Basically, environmentalism is a very selfish thing. it is all about protecting the environment so that we can carry on living. Over its life the earth has been a place where humans could never have survived, and in the long term (millions of years) it probably will be again. But right here, right now, we have to protect the geo-eco-system purly for our own sakes. Without it we simply cannot survive. It isn't about saving cute little furry things, its about making sure that you and I have somewhere hospitable to live in 60 years time that isn't entirely artificial. And no, we can't move all 6billion people to the moon or mars.

Re:Too much theories??

[HiQ]

Yep, that would be the same theory allright. It talked about the reduced 'pumping effect' in the area of Greenland (colder water sinks and it transported back to the caribean, to be replaced by warmer water). They said that this effect was measurably diminishing, and we could have another ice age on our hands. The big question is if humaity is causing all this, or are we just adding to an already present natural effect? This last assumption is not so strange - we have had quite a number of ice ages already. All the environmentalists are yelling that we are the cause of all this, but they easily forget the fact that there is natural occuring pattern of heating up and cooling down. Maybe humanity is a bit too arrogant to think that they are the *only* cause

Re:Too much theories??

[imipak]

You're referring to the thermo-haline circulation in the north Atlantic, aka the Gulf Stream. Warm water heads north east from the Gulf of Mexico, gradually cooling as it does so. It dumps a load more heat into the western European climate which accounts for our unnaturally warm climate. (check the temperatures of other areas on the same latitude: Siberia, northern Canada... etc.) As the water cools, it becomes denser and saltier (due to evaporation). This culminates in some areas off Greenland ("gyres") where the cold dense water sinks and heads back south to restart the cycle. The whole cycle takes several centuries.

However several rather frightening changes have been seen in the temperature and saltiness (haline) of various important currents off the northern coast of Scandanavia . One apocalyptic scenario is indeed for the Gulf Stream to shutdown, which would ****up western Europe nicely.

However this is a *local* effect in the context of the global climate. The whole system is *extremely* complex (chaotic, even) and hard to model or predict. Broad, long-period predictions are easier to make than short term ones - we can model nice equilibrium states, but it's highly likely that in the short term (a few hundred years) that the entire planet will see wild fluctuations in precipitation, temperature, sea levels, yadda yadda.

Ob links:

• UN IPCC Third Assessment Report: Summary (PDF) This is especially sobering reading; contributed to by ~1000 leading world authorities on the science)
• Intergovernmental Panel on Climate Change main site
• GEO-2000 report
• Worldwatch
• EPA Global warming site
• New Scientist special report

Note to the inevitable sceptics: if you accept (say) evolution, Relativity, Quantum mechanics (random eexamples) as being very very very likely to be true, then at least read the damn docs, look at the scientists who are putting their reps on the line on this, and consider whether it's more likely that we *are* affecting the global climate in unpredictable ways, or that vested interests are funding astroturf movements to try to convince American voters that it's all a commie plot...

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If the good lord had meant me to live in Los Angeles

Global heating = Global cooling

[Savage-Rabbit]

The latest Research seems to indecate that Global Warmin does not turn the earth into a Greenhous or a Sauna it triggers an Ice age.

How? Well the increased heating causes melting of the polar caps and increased rain fall, partickularly in the critical area of the Atlantic south of Iceland where the Gulf current heavy with warm salty water sinks to form a current that flows along the ocean floor into the Indian ocean where the current rises to the surface again. This system is called the "Great Conveyor" due to its similarity to a conveyor belt in a factory.

So why should we care about increased rainfall in the ocean around Iceland and holes melting into the N-polar ice cap.?

The reason we should care is that if the salty water in this area is dilluted the "Great Conveyor" will be cut. This means that the critical area where the Gulf current sinks moves south or the conveyor is cut alltogether.

What is the result of this development?

The Gulf current and its warm water is what makes large tracts of Europe and N-America habitable. So if the gulf current moves south we get a nasty cold period, a mini Ice age. If the Conveyor is cut we get a full blown ice age.

Contrary to popular opinion climatic changes do not happen sloooooowly they happen fast. We could see a the climate in say S-England change from what it is now to a type of climate that is common in N-Norway today within a human life time. This exact thing has happened before, the last time it happened was about 10.500 years ago when climatic conditions in S-England changed within 50-60 years to sub arctic conditions and remained htat way for over a thousand years.

Popular myths:

Climate changes happen slowly over hundreds of years! Wrong it changes fast and the changes are ill-predicteble.

The Global warming will cancel out the ice age! Wrong it causes the ice age.

I live far from the ocean and way south I should not worry! Wrong you should. All human kind should worry. A drop in temerature will cuse massive political an social upheval, crop faliures, famine and war.

The pollution quota system proposed by the US will help with the climate problem! Wrong selling liscences to pollute and produce greenhouse gasses won't help. Only an over all reduction of greenhouse gasses will help. Nature does not care about Pollurtion liscenses any more than God respects absoulution certificates signed by the pope, you'll go to hell anyway! ;)

So either we stuff a sock in the business lobbys mouth and make some relatively elementary changes to make energy consumption more efficient and industury and society more enviromentally friendly. Or we might be in for a long period of living in iglu's. And since I have been in an iglu I can tell you that you'll prefer to spend your lives in your cozy apartments.